General Industries Co. RC130 Schematic

General Industries Co. RC130

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Manufacturer:General Industries Co.

Schematics Content

Page 1:

a. Loosen Allen set.screw in trip finger spacer 561327 (fig. 16)
b. Move record shelf to 10 position and run changer through cycle to play position.
c. Insert narrow width .008 " feeler gauge (Part Number 88316) between lone arm support post and tone arm support bracket.
d. Hold spacer tight against small cork washer, and tighten set screw.
e. Remove .008 feeler gauge.

a. Place 10-inch record on turntable.
b. Lift up tone arm stop lever (561330 fig. 10) so that tone arm return lever will go all the way in toward main cam.
c. Place needle is starting groove on record or 3/32 " in from outside edge of record.
d. Loosen hex screw in tone arm crank.
e. Insert. 013 " feeler gauge (part number 88317) between large cork washer (60297 Figure 16) and trip finger
f. Set tone arm crank against outer edge of cutout in tone arm return lever (No. 561354 Figure 9). Hold tone arm crank in position pressed tightly against large cork washer and retighten hex set screw.
g. Remove .013 feeler gauge.
h. Run changer through cycle to see that no parts have been displaced that might cause changer to jam.

3. 12 INCH NEEDLE LANDING - See paragraph 4, Division D.

4. ERRATIC NEEDLE LANDING - See paragraph 5, Division D.

a. Trip finger passes over stud on main cam and fails to return to normal position due to improper clearance between trip finger and tone arm crank. Set clearance with .013" feeler gauge.

a. See that reject rod is on side of trip finger spring farthest from main cam. See Figure 14.

a. Check clearance between trip finger and tone arm crank. Should be .013". If correct, see that starting lever # 07329 Figure 18 is not binding
b. See that trip finger is not bent so as to strike stud on cam thus preventing actuation of starting lever.

a. Records undersize or holes too large or eccentric (not centered).
b. Incorrect distance from distance from spindle center to the edge of record shelf. See Division B
c. Stroke is insufficient.
(1) plunger arm part number 56975) does not make contact with the record support post cover plate. Indent plate slightly. Be sure the inside of plate is lubricated with lubriplate.
(2) Pivot for record plunger rocker arm (part number 55179) may be moved slightly inward to obtain greater stroke.

a. Failure to push records from flat portion of spindle. See paragraph 1. Division F.
b. Shelf lever # 561355 may be off can m track.

a. Check spacing from spindle center to edge of record shelf, See Division 1.
b. Record Record latch not dropping down.
(1) Failure to lift record stack clear of spindle.

(2) Sticking latch due to insufficient lubrication, pin fitting too snug.
burr on latch or bent latch.
4. SHUTS OFF BEFORE LAST RECORD JS PLAYED a. Tension of spring 64322 (fig. 7) too great. 5 DOES NOT SHUT OFF a. Automatic stop pawl 561323 (fig.
9) too tight. Release pressure be. tween wave washer and pawl using a screwdriver, b. Tone arm stop lever 561330 not flat against tone arm litt rasker

1. No response.
a. Audio systein. Check with radio reception.
b. Pickup leads shorted.
c. Pickup cartridge dead. Try new cartridge,

2. Distorted tone.
a. Worn needle.
b. "WOWS" or variance in speed.
(1) Oil on idler pulley and turntable rim
(2) "C" washer 561403 (under turn table) dragging on baseplate.
c. Warped records.
d. Defective pickup cartridge.
(1) Use of badly chipped records or records with breaks.
(2) Dropping tone arm on record.
3. Thumping noise
a. Groove in idler pulley worn by motor drive pulley. Result of idler pulley being held stationary with motor running
(1) Sand idler pulley smooth or replace pulley.
4. " Grid Hum ".
a. Insert phono input plug into phono socket as far as possible.
b. Check electrical ground connection of phono socket.
5. Mechanical Hum
Check alignment of turntable motor armature.

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(1) Lever for setting to play in - inch or 12 - inch records, Manual playing or Remove records. Mechanism as shown is set for playing in - inch records.

(3) Trip mechanism designed to handle automatically records with either spiral run-in or oscillating grooves. (4) Record Support Fingers.

(5) Turntable Shaft.

(6) Trip Rod Tension Spring.

(7) Adjustment for run-in or spiral grooved records.

(8) Adjusting lock screw for controlling position of power take-off wheel

(10) Adjusting screws for locking tone arm in position so that needle will rest properly on edge of record.

(12) Rubber-tired power take-off wheel. It is through the trip mechanism this wheel contacts the inside flange of the turntable during the change cycle from one record to the next, but does not operate during the playing of a record.

(13) Pickup Arm.

(14) Record Divide Fingers,

(15) Record Support Arm.

(16) Master Trip Cam.

(18) Reject Button. By pressing this button, changing mechanism operates immediately.regardless of needle position on the record. Also by pressing this. button, the first record will drop on turntable.

(21) Adjusting screw for setting vertical movement for pickup arm. If properly set, no further adjustment will be necessary.

(22) Adjusting Tie Bar used for positioning record support arms, The adjustment of this bar properly made should require no further attention.

(23) Rim Drive Electric Motor. Be sure Voltage and Cycles are collect for your Power Line.

(45) Trip Rod.

51) Rubber-fired Drive Wheel, By means of a spring this wheel tontacts the steel pulley on the motor and the inside flange of the turntable; driving the table in clockwise rotation.

(58) Cutter Arm. At all times, except when actually recording, cutter arm is placed on cutter arm support rest.

(60) Lead Screw.

(61) Adjusting Screw and Lock Nut for proper spacing between cutter arm and record.

(62) Cutting Stylus clamp screw.

(64) Adjusting Screw by which the tension on the cutter head equalizing spring may be varied for different types of records.

(69) Follower Arm and Spring Cam. This arm and cam mesh with lead screw (60) to provide lateral motion of cutter arm during recording.

Note: The Cutter Arm Support Rest holds cutter arm out of the way when automatic record changer is in use and also removes all strain on cutter-head equalizing spring. Mounted in inside position for shipping purposes. Before attempting to use mechanism it is necessary to move rest to the outside position shown.

How To Load Records
The record support posts must be set for either in - inch or 12 - inch records. This is accomplished by simply lifting Lever (1) then shift to the desired position. Select any number up to ten 12 - inch or twelve in - inch records, line them up with center holes, slip them onto center post of the turntable.

How To Start And Stop
All that is necessary to start the automatic Record Changer, after loading with records and properly securing needle in pickup,. is to turn on the current by throwing switch. After turntable is in motion, press button (18). To stop changer merely throw switch to off position.

How To Reject A Record
Press Reject Button (18).

How To Remove Records
Before removing records move Lever (1) away from turntable to extreme position. For Manual Playing Of A Record Move Lever (1) away from turntable to extreme position same as for removing records. This will free the trip ping mechanism so that the pickup arm can be moved by hand to and from the record.
NOTE: During recording Lever (1) must be in manual position at all times.

How To Place Record On Turntable
Place blank record disc on turntable in such a manner that the retractable pin protrudes through one of three holes near center of record. This is absolutely necessary to prevent the record from slipping and ruining the recording. When it is desired to play an ordinary record, place record on turntable; weight of record will cause pin to depress into turntable and friction between record and table is sufficient to prevent slippage.

How To Cut Records
Start motor, raise cutter arm from rest position to an angle of approximately 45 degrees and move inward until white mark on front of cutter arm is just inside record periphery. Lower arm gently as far as it will go; if stylus does not contact record, arm must be raised to relocate. The record is now being cut; inside limit of travel of recording arm will be indicated by a "clicking" sound, when this is heard, raise cutter arm immediately and place on rest. During time of cutting fine threads will accumulate about a inch inside stylus. These threads are carried to the center spindle by means of the thread collector attached to the cutter stylus clamp screw.

Phonograph Play - Back With phonograph reproducing needle in pickup arm (13) start motor and place arm on record.

Caution: Do not use changer mechanism with home recording discs.


For this mechanism to operate to the best advantage it should be mounted in a cabinet which is solidly supported and has no tendency to rock on its feet. If the floor under the cabinet is not level, shims should be placed under the feet of the cabinet until the base plate of this instrument is level.
Failure to level the instrument may result in improper feed-in of the pickup aim when the automatic record changer is in use and during recording the proper balance of the cutter head would be disturbed.

This mechanism will play in twelve inch or 12 ten inch commercial records automatically and an ordinary needle would become badly worn and cause serious record wear before the completion of this number of records. Special long playing needles made especially for automatic record changers should always be used. These needles are not as a rule recommended for playback of home recorded discs, however. For home recordings, 100 % shadowgraphed needles will give the least surface noise and prolong the life of the recording. These needles in turn are not suitable for use in an automatic record changer for playing a series of commercial records. No needle which has been used to play a commercial record should ever be used to play home recordings except in the case of the so called permanent point type ". Unless needles have a locating flat on the shank for engagement with the needle clamping screw they should never be used alter they have once been removed from the needle chuck. Even if needles have a. flat on the shank it is not always easy to locate them exactly as they were the previous time and serious damage to

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records may follow the re-use of such needles. The pickup needles used in this unit should be 5/8 inches long.


Frequent lubrication of the record changer is not required, however, certain points should receive attention at least two or three times a year. Lubricate with SAE 20 automobile engine oil (every six months or every 500 hours of operation whichever comes first) the following points: motor bearings (52) and (53), turntable shaft bearing under cam (16) and idler bearing (51). Caution: Make sure that no oil, grease, or solvent of any description gets on the rubber tread of idler (54). Oil other parts of the mechanism whenever advisable. Keep the working surfaces of cam (16) and the various cams on cam shaft (19) covered with a thin film of petroleum jelly (Vaseline).
Whenever the follower arm post (56) shows any tendency to stick or bind, in the pivot post bushing (57), apply petroleum jelly to the follower arm post above and below the pivot post bushing and work the lubricant in by alternately raising and lowering the recording arm (58).

Never oil the follower arm post. Work petroleum jelly into the bearing surfaces between the straddle plate (59) and the pivot post bushing (57). This can best be done by raising the recording arm (58) until it is free of the feed screw after which it can be swung from side to side until the lubricant is well worked into place.

Because the threads or shavings resulting from the recording process may work into the various parts of the mechanism, care should be exercised to remove this debris from the mechanism at regular intervals, At such times also thoroughly clean the threads of the feed screw (60), removing any dirt particles which may have accumulated. The use of a brush is recommended for cleaning the feed screw. Never use a sharp instrument to remove particles from the feed screw threads as scratches on the threads would be detrimental.


(1) In order to automatically change records, the record changer mechanism must first be put in motion. The trigger which accomplishes this purpose is the trip mechanism, The trip mechanism is actuated by the trip grooves at the end of the music grooves in all standard records
(2) All commercial records manufactured in recent years have either an eccentric (oscillating), or spiral (run-in) type of trip groove.
(3) This record changer will trip on any standard eccentric trip groove. It will also trip on any spiral trip groove provided that the spiral does not terminate at a larger diameter than that for which the trip mechanism is adjusted.
(4) To observe the operation of the trip mechanism, it is necessary to first remove the turntable and then move lever (1) to either the in or 12 inch position.
(5) To follow the action of the trip mechanism on eccentric trip groove records, it will be seen that as the pickup arm (13) swings inwardly, the trip rod (45) moves toward the pickup base until the serrations on the trip rod seen at (11) are in contact with the knife edge of the trip latch (24). If the pickup arm (13) is now moved outwardly, the serrations at (11) will engage with the trip latch (24) permitting the trip cam lever (3) to be released so that it will drop in and engage the trip cam (16).
(6) To observe the action of the trip mechanism on spiral trip groove records, swing the pickup arm (13) inwardly until the trip dog (7) comes in contact with the trip latch (24) and releases trip cam lift lever (3).
(7) The reject button (18) it will be noted also operates to trip the mechanism by imparting motion to latch (24).
(8) After trip cam lift lever (3) has been released so that it will engage trip cam (16), the forces required to operate the balance of the trip mechanism are derived from the motor (23) which drives cam (16) through the turntable.
(9) As trip cam (16) engages trip cam lift lever (3), cam (16) is hinged upwards so that it engages the pulley control lever (9) and forces pulley (12) into positive frictional engagement with the inside of the turntable rim.
(10) To keep pulley (12) in engagement with the turn table rim after lever (9) walks off of cam (16), lever (9) is engaged by latch (25) and the tripping operation is complete.


(11) Driven by the pulley (12) through a double worm and gear reduction, the cam shaft (19) carries cams which control the pickup arm movements, the dropping of records and at the conclusion of the change cycle, the release of latch (25).
(12) Cam (20) which is mounted on lower end of shaft (19) raises and lowers the pickup arm
(13) through a rocker arm and push rod. On the upper side of cam (20) is a dog which engages lever (17) and actuates the record handling fingers (4) (See paragraph 18). (13) The positioning of the pick up arm (13) for in or 12 inch records is controlled by two cams just above the lower cam shaft bearing. The lower of these cams (with short throw) positions the pickup for 12 inch records and the upper cam (with long throw) positions the pickup for in inch records.
(14) An examination of the pickup positioning cams will reveal spring fingers at the termination of the cam rise. These spring fingers are provided to urge the pickup needle into the starting groove on records which do not have lead in grooves.
(15) When lever (1) is set in the in or 12 inch position the pickup positioning cam follower is shifted up or down so as to engage the proper cam, The pickup positioning cam follower can easily be distinguished by the coil spring mounted thereon and linking the cam follower to its extension, This coil spring will extend, preventing damage, if for any reason the pickup arm (13) becomes obstructed while the pickup positioning cam is forcing the pickup arm (13) inwardly.
(16) Just above the pickup positioning cams is the pickup return cam which has the function of swinging the pickup arm (13) outwardly when the mechanism has been tripped.
(17) The last and uppermost cam operates through cam follower (26) to release the pulley latch (25) thus disengaging pulley (12) from the turntable rim at the completion of the cycle.
(18) On the upper side of the latch control cam is mounted a roller which engages the upper extension of lever (17) and through a linkage rotates the record support fingers (4) so as to drop a record to the turntable, After the record is dropped, the lower extension of lever (17) engages with the dog on the upper side of cam (20), rotating support fingers (4) in the opposite direction and back to their original position,


(19) To adjust the spiral trip to operate farther from the center of the record, loosen the set screw (46) holding dog (7) and move the dog (7) away from the end of the trip rod (45). (Read paragraph 20 before making adjustment).
(20) Dog (7) is set at the factory to trip when the pickup needle is 1-3 / 4 " from the edge of the hole in the record center. This standard setting is correct for all late recordings and all but a very few of the older ones. To facilitate the location of dog (7) it is best to hold a scale with the end touching the turntable pin (5) and in such a manner that the pickup needle will swing directly above the scale graduations. As noted above, the trip should release when the pickup needle reaches the 1-34 " graduation. Note: If for any reason the position of the pickup arm (13) with relation to the pickup base becomes changed, the trip dog (7) may require resetting. For this reason always check to see that the pickup is being lowered correctly onto the edge of the record before adjusting dog (7). (This pickup adjustment is covered in paragraph 34).

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(21) If the mechanism fails to trip always examine the trip grooves on the record first before attempting to make any adjustments. The record grooves may be badly worn or scratched in such a manner as to cause the pickup needle to jump the grooves. Also try a new pickup needle as the needle may have been damaged.

(22) The trip rod (45) is held in contact with trip latch (24) by the trip rod tension spring (6). If the eccentric trip fails to operate, it may be necessary to increase the pressure of spring (6) against trip rod (45) but before changing the adjustment, first, make sure that the trip rod does not bind in the bearing where it is linked to the pick up base, second, be sure that the trip rod floats freely, third, examine the serrations at (11) to be certain that the sharp edges have not been damaged, fourth, remove any dirt which may be embedded in the serrations and which would prevent the trip latch (24) from being engaged, fifth, examine the knife edge of trip latch (24) to see if it has become damaged, sixth, inspect the spring (6) to see that its long leg clears that part of supporting bracket (36) on which rests trip rod (45), seventh, make sure that the pick up needle is not jumping out of the trip grooves in the record, eighth, hold pickup base (50) with one hand, then press gently sideways on head of pickup arm (13) to detect any unusual amount of lost motion or play which might be caused by lock screws (10) not holding firmly or pivot
(47) not being correctly adjusted, ninth, sight along the length of the trip rod (45) to make sure that it has not become bent as this would seriously interfere with adjustment of spring (6). If trip rod (45) is found to be bent, always disassemble it before trying to straighten it. Note: Do not increase the pressure of spring (6) against trip rod (45) any more than is necessary to insure operation of the eccentric trip as excessive spring pressure will cause the pickup needle to jump the record grooves. To increase the tension of spring (6) against trip rod (45) loosen screw (27) and turn spring bracket (36) in a clockwise direction.

(23) If the pickup needle shows a tendency to jump grooves on all records and fails to trip, make sure that the pickup arm (13) swings freely. Next check the pressure of the pickup needle against the record to make sure that counter balance spring (28) is properly adjusted. (Model GI - RC130 should have a needle pressure of: 2-1 / 2 oz.: Model GI - RC130L: 1-1 / 4 oz. minimum). To correct insufficient needle pressure, loosen lock nut on adjusting screw (29) and turn adjusting screw (29) in a clockwise direction until needle pressure is correct. Caution: Before changing adjusting screw (29) make certain that push rod (- 0) moves up and down freely and is not supporting the pickup arm (13) while the needle apparently is resting on the record. Also make sure that pickup arm (13) is not resting on the head of screw (32). If the pickup needle only jumps grooves when but one record is on the turntable, pickup arm (13) is almost certainly resting on either push rod (30) or screw (32) in which case read paragraph 33. As a final precaution see that pivot screws (47) are not so tight as to interfere with the free vertical motion of pickup arm (13).

(24) If the trip mechanism still works in a faulty manner after the foregoing precautions have been taken. next check the trip latch (24) and the trip cam lift lever (3) to make sure that they work freely and do not bind on studs (35) and (48) respectively. If either of these levers are scraping on the base plate, make sure that the studs have not worked loose.

(25) If the lever (3) moves freely when it clears the trio latch (24) but does not swing into path of the trip cam (16) then spring (39) which connects to lever (3) is either stretched or missing. If lever (3) makes a loud click when it drops in, the rubber bumper. against which it should strike, has worked up and should be pressed back into place. Note: Never attempt to make the trip mechanism operate from home recorded discs.


(26) If the trip mechanism functions in a satisfactory manner and pulley (12) is latched in position to engage the turn table rim but does not contact the turntable rim with sufficient pressure to insure operation, loosen lock nut (77) and turn adjusting screw (8) counter clockwise so as to move the pulley control lever extension (49) outwardly a distance which will bring pulley (12) into positive frictional engagement with the turntable rim then tighten lock nut (77). Caution: This adjustment is very critical and should be carefully made.. If pulley (12) is forced too tightly against the turntable rim the latch (25) will stick at the completion of the change cycle and prevent the pulley from becoming disengaged from the turntable rim. Before making any adjustment it is also advisable to check the set screw in pulley (12) to make sure that pulley (12) is tight and not turning on the shaft which carries it.

(27) If latch (25) fails to hold pulley (12) in position, check the latch to make sure that the latch fingers have not been bent. Next check spring (41) on lever (26) 1 make sure that the spring is not defective or missing pulley (12) is riding off the lower edge of the turntable un or so high as to cause it to scrape against the underside of the turntable, the height of pulley (12) may be adjusted by means of thrust screw (44). Before trying to turn screw (44) always loosen the lock nut provided.


(28) If the mechanism repeats (continues to change records without playing them), the pulley (12) may not be dis engaging from the turntable rim. This failure to dis engage may be due to the following: Faulty action of the latch (25). (See "Caution" in paragraph 26). A defective or missing return spring (40) on pulley control lever (9). A defective or missing spring (41) on lever (26). Lever (26) may be bent so that it is not contacting the pulley release cam. (See paragraph 17).

(29) If pulley (12) disengages at the completion of the change cycle and immediately re-engages, the trip mechanism is at fault and it is suggested that the following be checked: Reject lever (42) may be bearing against trip latch (24) or it might be caught under trip latch (24). Pulley control lever (9) may be bent down so that it engage's cam (16) even when cam (16) is not elevated by lift lever (3). Cam (16) may be sticking in the raised position. The reset spring (38) on trip latch (24) may be defective u missing. The stud (34) on which pulley control lever (9) is mounted may have worked loose and should be tightened.


(30) If the mechanism trips during the playing of a record and before the pickup arm has swung inwardly to the point where the trip is adjusted to operate on spiral trip groove records, the following conditions should be checked: Weak or missing reset spring (38) on latch (24). Defective shoulder on trip latch (24) or rounded corner on cam lit lever (3), permitting lever (3) to slip off of the shoulder on trip latch (24). If the mechanism trips when the pickup arm is moved by hand from the outside edge of the turn. table outwardly the trip rod (45) may be bent.


(31) When lever (1) is moved to the manual position the pickup arm (13) should be capable of free motion between the normal limits of its travel without tripping the mechanism. If the pickup arm binds or trips the mechanism under these conditions check the following: Trip rod (45) may be bent or disengagement finger (37) bent or broken. If rubber bumper (2) becomes pushed up away from the base plate, this will permit lever (9) to overtravel and may jam trip rod (45).

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(32). If two or more records are dropped at the same time or one edge of a record drops and the other edge does not then the rear record support (15) may not be correctly adjusted or record separating fingers (14) may be bent. Also check the records to make sure that they are of standard diameter and thickness. Should record separating fingers (14) be bent refer to paragraph 35 for corrective measures. An examination of the unit will disclose that the front record support has fixed positions determined by dedents which are located by lever (1). The rear record support (15) however is adjustable. If the record supports are not the correct distance apart, loosen screws (22) and move the rear record support (15) to the proper position.

Caution: Before making this adjustment always make sure the lever (1) is firmly located in the proper dedent.

Note: As home recording discs differ from standard records in thickness and diameter, they cannot be handled by the record supports.


(33) The height to which pickup arm (13) is lifted during the change cycle may be adjusted by the screw (21). In making this adjustment make sure that the pickup arm will not lift high enough to strike the bottom record on the record supports. Also make sure that the pickup needle drops low enough to rest properly on one record on the turntable. (Recommended needle length 5/8 "). If the pickup arm (13) is in contact with the push rod (30) or the pickup rest (32) when the pickup needle is resting on one record on the turntable, the needle will not exert sufficient pressure against the record for proper operation. Before adjusting the pickup lift, therefore, the pickup rest (32) should be checked to be sure that it is correctly adjust ed. Pickup rest (32) is correctly adjusted when the pick up needle just touches the top of the turntable. As a final check be sure that the pickup will track properly when reproducing the thinnest home recorded disc likely to be used.


(34) To adjust the pickup arm (13) so that it will be lower ed to the correct point on the outside of the record, first shift the lever (1) to the in " position and then stop the mechanism with the pickup positioning cam follower at the point of maximum rise of the pickup positioning cam. (See paragraphs 13,14 and 15). Now raise the pickup arm to the vertical position and loosen two screws (10) so that the arm (13) can be moved with relation to the pickup base (50) but not too freely. Next holding the pickup base (50) so that it will not turn, force the pickup arm (13) toward the record centering pin (5). Now place a scale under the pickup needle with the end of the scale touching the record centering pin (5). Next, carefully pull the pick up arm (13) outwardly until the pickup needle is 4-45 / 64 " from the pin (5). Raise the pickup arm (13) and tighten the two locking screws (10), being careful not to move arm (13) outwardly past the correct setting before tightening the screws. This adjustment will automatically. take care of 12" records as well as 10" as will be seen by moving lever (1) to the 12" position and running the unit through its cycle. If the pickup arm (13) always lowers in the 12 " position, regardless of the position of lever (1), the pickup positioning cam follower is sticking in the down position. Some pickups are equipped with an eccentric (31) for rotating the pickup arm (13) with relation to the pickup base (50). On such units the two locking screws (10) are loosened and eccentric (31) turned a small amount at a time until the pickup needle is lowered to the correct point on the record,


(35) The record supports (4) and the record separating fingers (14) are so designed that no chipping of standard records will take place unless through rough handling the fingers (14) become bent. For proper operation the fingers (14) must be perfectly flat. To straighten the fingers (14) it is necessary to remove the large headed screws (55) which hold the fingers in place after which the fingers (14) can be disassembled. Ordinarily straightening can be accomplished by holding the main part of finger (14) through which the clamping screw passes with one hand and then taking hold of the sickle shaped part of (14) with the fingers of the other hand, bending the sickle shaped part until it is lined up with the main body. After bending lay the finger (14) on a flat surface to make sure the straightening has been properly done.



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(167 A suggested circuit for inclusion of the magnetic cutter in the voice coil circuit is shown in Figure A.
In this circuit, the speaker is used as a monitor. Resistor R2 shunts the speaker voice coil and resistor R: shunts the cutter. Resistor values are selected which will result in the total series resistance of the two groups approximately matching the output transformer's impedance. The ratio of Riin ohms in parallel with Zc in ohms at 400 cycles to Ry in ohms in parallel with Zy in ohms at 400 cycles will represent the voltage ratio between cutting and monitoring levels. This can be converted to decibels when the resistance of each leg of the network is known. The high frequency response of the cutters is partially governed by the ratio of Zc to R1. Resistor R1 should be of the same value as the impedance of Zc or slightly higher, but should in no case exceed twice the value of Za in ohms. In al calculations, sufficient accuracy will normally be Sextured if the 400 cycle impedance of both cutter and speak er voice coil be considered as pure resistance. Generally speaking the 400 cycle impedance in ohms of a magnetic culier will be approximately 21 times its D.C. resistance irt ohms. The 400 cycle impedance in ohms of the speak er voice coil will be approximately 14/4 times its D.C. re sixiance. If the 400 cycle impedance in ohms is supplied by the manufacturer of the cutter or speaker, it should be used instead of calculations from the D.C. resistance.

(37) Typical values for Ri and R2 with various impedance voice coils are given in the above table when a 4 ohm D.C. - in ohm 400 cycle cutter is used. Value of R and R2 can be found with other impedance cutters by simply applying Ohms Law if, as mentioned before, the 400 cycle impedance in ohms is considered as pure resistance.

When connecting the cutter to an output where the monitor speaker isn't required, only Ri in parallel with Zc in ohms will be considered as the load. For example, a in ohm cutter at 400 cycles (2c) in parallel with a 16 ohm resistor (R1) would represent a load of 6.15 ohms to the output transformer of the radio receiver or amplifier. It would be satisfactory to connect this to the 6 ohm tap of the output transformer.

(38) A volume level indicator is necessary to prevent cutting too heavily. For this purpose, a high resistance voltmeter (1000 ohms per volt or higher) can be connected across the cutting head in parallel with R1. Where Zc has a value of 10 ohms as shown in the table, the voltage peaks should be about 1 volt on speech and 11/2 volts on music. A power level of approximately 44 watt is required by the average magnetic cutter for satisfactory operation. This is a voltage of 1.58 across a in ohm impedance cutter,

Other methods of volume level indication such as neon bulbs in series with resistors, tuning eyes, oscillographs, etc., are also satisfactory. Any high impedance device which will indicate low values of A.C. voltage can be used.

In cases where it is necessary to extend the cutter lead wires, insulated # 20 wire should be used. When the extension is over a few feet it is usually desirable to use a larger wire size.


(39) To record at characteristics similar to standard commercial recordings with a crystal cutter, a 50,000 ohms 1 watt resistor should be placed in series with the cutter. To emphasize high frequencies, this resistor should be shunted with a condenser between. 001 to. 01 mfd. To emphasize low frequencies, the series resistor should be varied up to 250,000 ohms.

(40) A volume level indicator is necessary to prevent cutting too heavily. The level indicator should be connected as V.I. in figures B, C and D. Any high impedance device which will indicate A.C. voltage can be used. A high resistance A.C. voltmeter (1000 ohms or more per volt) 0-150 volt scale may be used. For normal recordings, the voltage peaks should be about 100 volts. The actual voltage required can be determined after a few trial recordings are made (see section on Making A Trial Recording).

(41) A crystal cutter must be driven from a high impedance source, Figures C and D show means of capacity coupling the cutter to either a single or push-pull output circuit. The 0.5 mfd. 600 volt condenser blocks the direct current from reaching the cutter but will pass the voltages to be recorded. Resistors and R2 represent legs of an "L" rad to be used in attenuating the speaker level to permit its being used for monitoring when recording a radio program. These two resistors may be fixed and of such values that the total load to the output transformer will be the same as the speaker impedance. The monitoring level will be a fixed number of decibels below the recording level. See Chart E for typical values of Ri and R2. Various degrees of monitoring attenuation can be found by simply applying Ohms Law if the 400 cycle impedance of the speak er voice coil is considered as pure resistance. A simple switching arrangement can be used to remove the resistors from the circuit as well as opening the cutter circuit when not recording.

Figure B indicates a means of inductively coupling the cutter to an amplifier's 500 ohm output. Transformer Ti should have an impedance ratio of 500 to between 40,000 to 80,000. Several reputable transformer manufacturers supply transformer which can be used-some are designed primarily for crystal cutters and others are for driving push-pull grids from a 500 ohm line. If the latter transformer is used, the center tap of the secondary will be left open as shown in Fig. B.

The length of the wire from the radio or amplifier to the crystal cutter should be kept as short as possible and should be well insulated.

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(42) The amplifier should be capable of at least 5 watts out put in order to keep harmonic distortion down to a reason able level and preferably have triode output or beam tubes with inverse feedback. Frequency response should be reasonably flat within the audible range. Hum level should be low enough so that hum is not discernible at the loudspeaker with the volume adjusted to recording level. The amplifier should be stable at full volume and "microphonic" tubes avoided. If the amplifier and recorder unit are to be installed in the same cabinet, all conditions of mechanical resonance and feedback must be avoided to preclude the possibility of recorded "rumble". The cabinet should be substantially built of comparatively heavy materials, If cabinet resonance is encountered, wooden braces glued to the inside surfaces of the cabinet will sometimes serve to correct this condition.


(43) For radio recording, it is desirable to leave the speaker connected for monitoring purposes. In Fig. A the circuit components are arranged for reducing the speaker volume during recording as shown in the table.

(44) Referring to Fig C and D, an "L" pad is shown in the voice coil circuit for reducing speaker volume during recording When the radio is being used without recording this "L" pad should of course be disconnected.


(45) When recording from microphone the speaker must be disconnected to prevent feed back and a resistor of the same value as the speaker voice coil impedance substituted for the voice coil, in order that the proper load impedance be reflected back to the output tubes.


(10) The crystal pickup leads may be connected directly to the phonograph input terminals provided on most amplifier's and radio receivers, or may be connected between "grid" and "ground" of the radio receiver's second detector tube if no other connection is provided.
The volume control is usually in this circuit and the pickup lead can be connected to the two outside connections of potentiometer type volume controls. One of these connections is grounded, or at very low potential. The shield or outer conductor of the pickup wire should be connected to this terminal. The inner wire of the pickup lead should be connected to the opposite volume control connection. If desired, a single pole double throw switch can be used at this point to switch from radio to phonograph. If these connections are reversed, an A.C. hum will be heard in the loud speaker when the switch is in record playing position.


(47) For inaking microphone recordings through the audio amplifier of a radio receiver, quite satisfactory results will usually be forthcoming by use of a diaphragm type crystal microphone of reputable manufacture, connected to the phonograph input terminals of the radio receiver. Correct polarity of connections to the microphone cable should be observed, the same as for connecting the pickup cable. The shield of the cable should connect to " ground. " This arrangement will usually afford sufficient volume for microphone recording, although the microphone cannot be expected to produce the same loud speaker volume as is obtained in playing records with the pickup connected to the amplifier. The phonograph pickup delivers approximately from. 5 to 2 volts to the input of the amplifier, while the microphone is capable of furnishing only approximately 1 / 100th of this voltage or from. 01 to. 02 volts.


(48) If it is within the scope of the constructor's knowledge and ability, the assembly and installation of a microphone pre-amplifier will prove to be a material aid in microphone recording service. The purpose of the pre-amplifier is to amplify the impulses generated by the microphone, before being fed into the audio frequency amplifier, so that the amplifier will produce about the same amount of volume to the recording head, or cutter, whether recordings are made from microphone or from radio reception.


(49) This mechanism is designed to utilize short shank styli or cutting needles. Short shank styli have an overall length ranging from 9/16" to 5/8" whereas long shank styli are approximately 1/8" longer. Any attempt to use long shank styli will result in failure as it will be found impossible to correctly adjust the stylus angle (see "Stylus Angle Adjustment"). It is also essential that the cutting face of the styli le parallel to the axis of the shank, Styli having a hooked (utling face are offered for sale but as in the case of the long shank type, these cannot be used in this mechanism.

(50) Short shank, straight face cutting styli are sold at widely varying prices depending on the material and care used in their manufacture. The most inexpensive type is made from hardened steel and the cutting point is ground to a sharp "V". In contrast the higher priced styli are tipped with special metal cutting edges such as stellite or precious stones such as sapphire and the cutting points on these are ground with a slight radius. The useful life of styli ranges from 30 minutes in the case of steel styli to as much as 10 hours in the case of natural sapphire styli, but it must be remembered that the abrasive character of the l'ecorang bianks used will finally determine the actual life of any given stylus. Care must also be exercised to prevent the sharp cutting edges from coming in contact with hard surfaces, such as the turntable, which would render the stylus unfit for further use.

(51) Almost all recording styli, now on the market, have a flat cut on the shank. This flat is oi great assistance in properly locating a stylus in the cutting head as the stylus sciew bears against this flat and holds the stylus in proper position. When styli are used which do not have the locating flat, it is usually difficult to properly position them in the cutting head. Even where styli have the locating flat cut on the shank, they do not always position themselves in the stylus chuck so that the thread cut from the record disc will throw toward the record center. In case the thread tends to throw to the outside, loosen the stylus clamping screw slightly and reseat the stylus in the stylus chuck.

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(52) Due to the wide range of physical properties found in various recording blanks and the varying cutting qualities of different styli, it is necessary to adjust the cutting head on this unit for the particular type of recording blank and stylus to be used if best results are to be realized. To compensate for these differences in recording materials. two adjustments must be made. First, the proper angle must be maintained between the cutting face of the stylus and the face of the record disc. Second, downward pressure of the stylus against the record must be correct. (See "Stylus Angle Adjustment" and "Depth of Cut Adjustment.")

(53) Owing to the fact that the shanks of cutting styli are or hardened steel, there is a tendency for styli to become loose in the stylus chuck during the recording process. combat this tendency, the stylus clamping screw should be tightened with the fingers at the completion of each recording. Never tighten the stylus clamping screw with pliers, however, as breakage of the clamping screw is almost certain to occur.



(54) The angle between the cutting face of the stylus and the face of the recording blank is said to "lead" when the angle is greater than 90 and is said to "lag" when the angle is less than 90. Approaching the vertical, a point will be found where the cut becomes cleaner and quieter. however. a point is always reached where the stylus tends to dive into the record face and when this happens, chaiter and squealing occur. For this reason the useful limits of adjustment are from the vertical to 5 lagging. Because of the sharp "V" point found on hardened steel styli, this type usually operates best at about 5 lagging angle. Sapphire styli on the other hand can usually be adjusted between the vertical and 5 lagging angle. Stellite and other alloy styli will be found to fall somewhere between steel and sapphire and usually can be operated almost vertically. It should be noted that when a stylus becomes dull from normal wear, surface noise increases and eventually chattering or squealing occur Chattering or squealing can also be caused by a recording blank which does not cut freely because it has become dried out or else did not have good cutting qualities initially. All of these factors must be considered when adjusting the stylus angle.

(55) The stylus angle is controlled by the length of the stylus and the distance from the top of the recording blank to the recording arm (58). As the stylus should always be inserted in the stylus chuck as far as it will go, it follows that to change the stylus angle the recording arm should be raised or lowered. Raising the recording arm decreases the lag and lowering the recording arm increases the lag. To change the height of the recording arm (58) above the record blank, first raise the recording arm to the vertical position and then adjust stop screw (61) until stylus angle'is correct.

(56) To determine the angle between the cutting face of the stylus and the top of the record blank at any time. two methods of inspection are used. (a) With the turntable stationary and the stylus resting on the record blank, a sight taken across the cutting face of the stylus and one side of the spindle in the center of the turntable will show any departure from the vertical and how much. (b) Looking across the cutting face of the stylus, both the stylus and its reflection in the face of the record blank can be seen at one time. When the stylus is vertical with respect to the record blank, the plane of the cutting face of the stylus and its reflection will of course be in a straight line. When the mechanism is mounted down in a well in a cabinet it is not always possible to make these inspections directly and in this case a mirror must be employed.

(57) The most important thing to remember in making this adjustment is that the best stylus angle is that angle which gives the quietest cut and plays back with the least surface noise.

(58) Caution: Because of the wide variation in the thickness of record blanks (.020" to .100"), the variation in the length of styli ("9/16 to 5/8") and the possibility of warped or bent recording blanks, be sure that the stylus clamping screw (62) does not strike the bottom of the slot in the end of the recording arm as the stylus follows the surface of the record blank. Also, be sure that the cork bumper (63) on top of the cutting head is not striking in the top of the recording arm. If it is suspected that the cork bumper is striking, this can be easily checked by gently applying upward pressure on the stylus clamping screw (62). 1 will raise easily if the cork bumper is not striking but do not lift this screw roughly as it might become bent.

(59) Caution: Every care should be exercised to prevent the cork bumper from striking in the top of the recording arm during recording as this would drive the cutting stylus through the coating on the recording blank and ruin the cutting edges of the stylus. The stylus may also be damaged if it is lowered roughly on to the face of the recording blank, Never allow the stylus to rest on a stationary recording, blank if energy is being fed to the cutting head, as the stylus will dig through the record coating and damage its cutting edges.


(60) The depth of cut is regulated by screw (64) located on top of the recording arm (58). Turning screw (64) clockwise increases the depth of cut. To check the depth of cut, make a trial cut of a few quiet grooves on a record blank of the same type on which recordings are to be made. This is important because of the varying hardness and cutting qualities of different blaniss. For an accurate inspection of the grooves, a magnifying glass or low powered microscope should be used to compare the width of the grooves with the land or uncut space between grooves. If a magnifying glass is not available, the examination can be made with the unaided eye provided the light strikes the record at the correct angle. When a magnifying glass is not used. how. ever, the grooves appear to be wider than they actually are and this should be born in mind. For home recording practice, a groove exactly the same width as the land, is recommended. Too narrow a groove will cause difficulty with the playback needle climbing out of the groove, while at the other extreme a very wide groove will cut across into the adjacent grooves during recording. Too wide a groove may also produce sudden variations in the turntable speed.

(61) Hardened steel styli with a sharp "V" point cut deeper for a given pressure than the higher priced styli which shive a very slight radius on the point. As styli become dulled with use more pressure is required to maintain the same depth of cut. Changing the cutting angle (angle between the cutting face of stylus and face of record) will have some effect on the depth of cut and for this reason the stylus angle adjustment should always be made before the depth of cut adjustment, where both adjustments are necessary.

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(62) If recordings are made at too low a volume level, it will be necessary to increase the gain during playback to where surface noises will be very objectionable. If on the other hand the volume level is too high, the wall of record material between grooves may be cut through, rendering the racord useless. Where only a very thin wall is left between grooves, "echo" or "ghost" may be noticeable. "Echo" is the faint reproduction of recorded sound as the playback needle travels in the adjacent groove following the groove in which the sound originally was recorded, while "ghost" is heard in a groove preceding an adjacent groove where the sound actually was recorded.


(63) After it has been determined that all of the adjustments are in correct order, and the machine is cutting correctly, a trial cut should be made to determine the correct level of volume for recording.

(64) During recording, the tone control should be set to its treble or high pitch position to avoid the possibility of losing high frequencies in the recording.

(65) In making microphone recordings, place the micro phone at a distance of about 10 to is inches for the speaking voice, and at correspondingly greater distances for recording vocal or instrumental musical renditions. When recording speech, the microphone should not be spoken into at close range, as lip sounds and sounds of breathing will be recorded, and because of shock to the microphone diaphram due to sudden bursts of sound impulses entering the microphone, the voice is caused to be recorded unnaturally.


(66) The recording arm assembly is automatically positioned for height at the pivot or back end by the "U" shaped tank (65) and the follower arm post (56). If the recording i'm assembly does not always come to the same height when the recording arm is lowered to the horizontal position, check spring (66) and also make sure the follower arm post (56) is not binding in the pivot post bushing (57). If 10k (65) is loose when the recording arm is lowered to the horizontal position, this is an indication that something is wrong. If the follower arm post (56) is binding in the pivot post bushing (57), trouble may also be experienced when trying to raise the recording arm from the horizontal position. To stop any binding between the follower arm post (56) and the pivot post bushing (57) apply grease as outlined in the section on lubrication.

(67) Two hex-head set screws (67) secure the recording arr assembly to follower arm post (56). If the hex-head screws (67) become loosened or the relationship between the recording arm platform (68) and the follower arm (69) become altered in any manner, make sure that both of the following conditions are complied with. (a) The end of the follower arm post (56) should extend through the recording arm platform (68) approximately 1/32 ". Note that this dimension is taken from the top surface of the platform (68) and not from the staked end of the bushing attached to the platform. (b) With the follower arm (69) swung in to where it is in contact with the stop (70), the recording stylus should be cutting a circle approximately 3 inches in diameter. If the spring blade on the end of the follower arm strikes the casting carrying the feed screw before the follower arm strikes stop (70) or the knife edge (71) can no longer engage the feed screw threads, loosen screw (72) and reset stop (170). When resetting stop (70) make sure that knife edge (71) will still engage with the threads of the feed screw (60) when recording at the outside of a 10 inch diameter record blank.

(68) Caution: Any time that the recording arm mounting is adjusted, it is always necessary to readjust the tension screw (73) (See "Proper Engagement of Feed Screw").

(69) If after hex-head set screws (67) are properly tightened there is any lost motion between the recording arm and the follower arm (69), check the adjustment of the pivot screw (74). When pivot screw (74) is properly adjust ed there should be no lost motion between the recording arm (58) and the recording arm platform (68).


(70) Engagement between the knife edge (71) and the feed Screw (60) usually starts to take place when the nose of the recording arm is around 2 inches above the turntable. When The recording arm (58) is raised to a greater height than this, unhampered horizontal motion of the recording arm is possible between the normal limits of its travel. To per init disengagement of the recording arm from the feed screw at a minimum height above the turntable, stop screw (73) has been provided. Adjustment of screw (73) should be made with the recording arm in the lowered position and with the feed screw engaged. Adjust screw (73) so that it barely touches spring blade (75) when the knife edge (71) is engaged at any point in the length of feed screw (60).

(71) Normally the full pressure of knife edge (71) against feed screw (60) is desirable. If this pressure is sufficient to cause uneven turntable speed, however, the pressure of knife edge (71) against feed screw (60) can be reduced by turning screw (73) in a clockwise direction. Great care should be used however in reducing the blade pressure as uneven grove spacing may result,


(72) If screw (73) is turned too far, in a clockwise direction, it will reduce the pressure of the knife blade (71)
gainst feed screw (60), to where the knife blade (71) will climb the sides of the threads in the feed screw and cause uneven spacing of the recorded grooves in the record disc. Always be sure that the threads of feed screw (60) are free of dirt or other foreign matter, as these particles may cause uneven spacing of recorded grooves. Excessive end play in the feed screw will also cause uneven groove spacing.

(73) Thrust screw (76) is provided to keep the end play out of feed screw (60). Care must be used in adjusting screw (76) to prevent binding feed screw (60) between the end thrusts'as this would put an excessive load on the motor and cause speed variations in the turntable.

(74) Lost motion or play between the follower arm (69) and recording arm (58) in the horizontal direction will prevent the recording arm from accurately following the fol lower arm, and this play should be eliminated (See "Adjustment of Recording Arm Mounting" paragraphs 67 and 69).


1. Remove the stylus screw (62).
2. With the arm (58) in the vertical position, press the balance spring against the top of the arm which will throw the cutter head out where it can be firmly grasped.
3. Pull the cutter head upwards until the knife edge at the back of the cutter clears its seat in the arm.
4. Unhook the balance spring from the cutter head.
5. It will now be noticed that a cork bumper (63) is glued to the top of the cutter head. This bumper is put there to prevent the stylus screw from being bent if the recorder arm is roughly handled. Remove this cork from the old head and glue it to the new head in precisely the same location as before.
6. Hook the balance spring to the new cutter head and extend the spring sufficiently so that the cutter head knife can be placed in its seat in the arm.
7. Replace stylus screw with shaving collector between cutter head and cutter arm with bottom of collector to left of center.
8. Thread the cutter leads through the arm, the arm platform, the base plate and the leads clamp on the underside of the base plate and arrange them exactly as before.