General Instruments Corp. 204 Schematic

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Manufacturer:General Instruments Corp.

Schematics Content:

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The Model 204 Record Changer is an automatic cam type changer, featuring Single Button Control, Automatic Shut - Off, and Eccentric Spindle Record Selection.

Single Button Control... Initial depression of the Single Button Control (6) not only actuates the Mercury Switch (13) but at the same time contacts the Automatic Trip Bar (14). The motion of the Automatic Trip Bar (14) causes the Carrier Lever (31) and its attached Drive Wheel (10) to swing outward until the Drive Wheel (10) comes in contact with the rim of the turntable. The consequent revolving motion of the Drive Wheel (10) is transmitted to the Main Cam (15) through a Drive Spring (16) and Worm Drive (17) assembly.

Cycling... A single revolution of the Main Cam (15) results in complete automatic cycling of the changer. This includes selection of record from stack, lifting Pick - Up Arm (1) from rest position and setting needle on edge of record. Upon completion of the revolution, the Automatic Trip Cam (24) engages with the block on the Trip Lever (43) and pulls the Carrier Lever (31) back to its original position so that the Drive Wheel (10) is no longer engaged with the turntable rim.
Record Feed... The lower side of the Main Cam (15) controls record selection. Motion of the Feed Carn Roller (36) about the cam results in a backward and forward movement of the Feed Sector Lever (19) thus engaging the Record Feed Pinion (20). This in turn causes the Eccentric (35) to first rotate to proper position for record selection and to then return, allowing record to drop over Spindle (3).

Pick - Up Arm Movement... The upper side of the Main Cam (15) controls Pick - Up Arm (1) movement. Lift is effected by motion of the Lift Pin (25) along the vertical edge of the cam as the latter rotates. Direction is controlled by the engagement of the Main Cam (15) with the Sweep Lever Pinion (26). The Sweep Lever (27) is attached to the Pick - Up Arm (1) by means of a Clamp (28) around the Pick - Up Arm Pivot Sleeve (29). A boss projecting from the upper side of the Main Cam (15) displaces the Stop Lever (30) at the end of the change cycle, thus permitting the Pick - Up Arm (1) to proceed across the record.

Positive Trip Action... As the Pick - Up Arm (1) approaches the spindle assembly, the Sweep Lever (27) hits the Positive Trip Screw (37) mounted on the Trip Lever Assembly (43). This action re-engages the Drive Wheel (10) with the turntable rim and starts a new cycle.

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Pawl Trip Action... Any reversal of the direction of the Sweep Lever (27) travel before positive trip action takes place causes the Sweep Lever (27) to push forward the Pawl (38) mounted on the Auxiliary Trip Lever (34). This movement also has the effect of re engaging the Drive Wheel (10) to start a new cycle. (Pawl trip action is effective only after the Pick - Up Arm (1) reaches a distance of not more than four inches from Spindle (3).)

Ten Inch or Twelve Inch Operation... Adjusting the Record Support (4) to the ten inch or twelve inch position lowers the Selector Rod (39) a definite degree. The length of the extension of this rod determines the position of the Stop Selector Lever (40) which in turn con. trols the Stop Lever (30). The latter is the means of regulating the distance the Sweep Lever (27) and its attached Pick - Up Arm (1) travel before the Pick - Up Arm (1) is lowered to the edge of the record. (Operation of this feature is dependent on proper positioning of Record Support (4). Always turn Record Support (4) to full stop.)

Automatic Shut - Off... Release of the Record Stabi. lizer Finger (5) lowers the Shut - Off Rod (41) and forces the Stop Selector Lever (40) completely clear of the Stop Lever (30). The latter is then able to move into a position which completely blocks any forward motion of the Sweep Lever (27). Consequently, the Sweep Lever (27) cannot perform its usual function of actuating the Switch Lever (32). Thus the Switch Lever Roller (33) remains in the path of the Stop Lever (30). On completion of the cycle, the Stop Lever (30), in returning to home position, hits the Switch Lever Roller (33) and forces the Mercury Switch (13) to the OFF position.

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Changer trips before completion of record:
Turn Positive Trip Screw (37) clockwise.

Changer fails to trip after completion of record:
Turn Positive Trip Screw (37) counterclockwise,

Drop point of Pick-up Arm is not at proper point on record:
Loosen screw on Sweep Lever Clamp (28) slightly and reposition Pick-up Arm (1) with respect to Sweep Lever (27).

Slow turntable speed:
Make sure Drive Wheel (10) does not strike rim of turntable. If necessary, readjust eccentric bushing on Drive Wheel (10). (Note: This adjustment should be exceedingly slight as a large movement may Cause continuous trip.)
Check for grease or oil on Idler Wheel (9) of Motor (11) and inside of turntable. Wipe with carbon tetrachloride.
Check for sticky Idler Wheel (9) plate on Motor (11). Free with screw driver.

Stalls in cycle:
Remove any grease on Drive Wheel (10) or inside of turntable with carbon tetra chloride.
Check mesh of Worm Drive (17) and Main Com (15) for proper clearance. Loosen screws on main bracket and tighten. (See Figure 5.)
Check for bind in Spindle Assembly (See Figure 6). Disassemble index collar and Record Feed Pinion (20), remove Spindle Cap (2), Eccentric (35) and eccentric rod.
Check for freeness and remove binds.
The following cautions should be observed in reassembling Spindle Assembly:
(a) Reassemble with a maximum end play of. 005 between Eccentric (35) and Spindle Cap (2)
(b) The Eccentric (35) should be in line with the Spindle (3) when the changer has completed its cycle.
(c) The Feed Sector Lever (19) should mesh with the Record Feed Pinion (20) as shown in Figure 6.
(d) Align Spindle Cap (2) with Spindle 13) in detent position.

Records fail to drop:
Check meshing of Feed Sector Lever (19) vith Record Feed Pinion (20). Reset as shown in Figure 6.

First record does not play:
Readjust end of Lift Pin (25) so that needle will play first record. (See Figure 7.)
(Note: Do not bend Lift Pin (25) too much as this will prevent playing of top record on full stack.)
Make certain that pick-up lead does not hit top of Lift Pin (25) or hinge.

Automatic Shut - Off fails to operate:
Make certain that the Automatic Shut - Off Adjusting Screw (42) mounted on Stop Selector Lever (40) makes contact with the Shut - OH Adjusting Rod (41) when the Stabilizer Finger (5) is released. Adjust as required. Check leads on Mercury Switch (13) for interference with Switch Lever (32) motion. Check Mercury Switch (13) continuity.

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