P.R. Mallory & Co. 70 Schematic

P.R. Mallory & Co. 70

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Manufacturer:P.R. Mallory & Co. (Elkon)

Schematic Pages

PNG: Page 1 Rider Manual Volume 5

Schematics Content

Page 1:

Directions for Replacing Contact Spring and Reed Assemblies in the 1933 and 1934 * 60 70 and 80 Series Mallory Self - Rectifying Elkonodes ROUTINE FOR DISMANTLING ELKONODE: (a) Remove screws holding cover on can. (b) Loosen cover from can and hold in upright position, prongs down: gently shake the rubber sock and Elkonode from the can.

(c) Closely observe the manner in which the leads from the prong base to the Elkonode are placed in the outer slots of the rubber sock. This is important for correct placement of wires when replacing assembly in can.

(d) Observe the location of the various parts, especially the position of the reed Amature (2) with respect to the coil pole shoc of the Elkonode (1).

(e) For your own protection, it will be well to make a pencil sketch of the manner in which the five leads are connected to the Elkonode terminals, before removing these leads. Do not cut them to remove, but carefully unsolder each one. In the 60 and 70 series unite, where Condensers are supplied internally, remove them also and unsolder the coil wire at the spring lug.

(t) Remove coil mounting screw from end of frame, and remove coil and pole shoe from frame. Loosen lock nuts A - I, A -
2. C - I and C-2 and remove adjusting screws B -
1. B - 2, DI and D -
2. Remove the insulating bushings from the slots in epda of springs. (1) Loosen stack screws (3) and remove. Press on the under side of the bakelite stack and reed xo as to move the assembly out from between the frame. Save the insulating bushings (5), stack screws (3), connector plate (4), adjusting screws, and the lock nuts. Remove the bakelite stack spacers and insulating tubes from the assembly.

ROUTINE FOR REBUILDING THE ELKONODE: (h) Rebuild the stack assembly (unless you are using stack assembly complete as provided under our part Number A 18448). making sure to use the thicker of the four bakelite spacers on either side of the reed. Make sure that in assembling the springs, the lugs for soldering line up on the outside edge of the stack

(i) Since the Elkonode is largely magnetic in operation.extreme care must be taken to prevent particles or filings of iron from attaching themselves to the iron parts of the Elkonode. Clean the pole shoe, frame, and reed thoroughly.

6) Hold the assembly with the reed in the position shown in illustration, (see page 2). Place the frame under the Assembly, as shown also, and insert the assembly from the top. It may be necessary to spread the frame slightly in order to make the insertion. Inspect the stack screws for signs of weakening, and if satisfactory, replace with the connector plate and tighten slightly. (k) Reinsert the driver coil and pole shoe and clamp in place with the screw removed previously. Draw the screw up

tightly, and with long-nosed pliers, turn the pole shoe to a vertical position parallel with the teed surface. The coil wire should be inserted through the hole in the frame before the coil is inserted in the frame,

1) The reed should stand approximately in the center of the frame at rest. The end of the reed should be parallel to the face of the pole shoe, and from. 003 " to. 005 " distant from it when the reed is pulled down opposite its center. Thio distance should be accurately act by feeler gauges. The reed may be adjusted because of play in the mounting holes.

(m) Insert the insulating bushings in the slots in the ends of the springs, thread the adjusting screw into place, together with the lock nuts. Adjust the screws to place the contacts close to the reed contacts. The springs should be moved so as to allow the contacts to strike the rood contacte without over lapping. The contacts should be fairly flat in making contact, and still not bind on the insulated adjusting bushing.

(n) Tighten the stack firmly without disturbing the adjustments.
Hold the reed, over a piece of white paper in the vertical position shown in illustration, (see page 24). The end edge of the reed, on the opposite side from the armature should rest from Auch with the edge of the pole piece to. 003 above same. Any bending of the reed should be done at the extreme armature end, and only slight alterations should ever be necessary. Should the pote shoc not be parallel with the armature in a vertical direction, turn the pole shoe with a pair of long-nose pliers, do not attempt to twist the reed. Check the air-gap spacing and tightness of coil mounting screws, if such adjustments are made, then recheck alignment.

() Solder the leads to the spring, and reed lugs after threading all into place first. It condensers are to be used, place them in position and solder the leads from them at the same time. Make sure that the insulation in over the "hot" condenser lead and that it does not "short" against the frame. Also make sure that the grounded lead does not touch the spring lug or wire. Solder the coil wire at the same time, and solder the connector plate lug to the reed tail. It is suggested that you use another Elkonode as a sample, since it is quite important that all wires be replaced exactly as removed.

() Some method of exerting high pressure upon the stack end of the Elkonode while the final tightening of the clamping screws is taking place is essential. It is suggested that an Arbor press, capable of exerting a total pressure of about 2000 pounds, be used. Pressure should be exerted directly over the stack, between the screws, while a large screwdriver draws the screws down firmly. This prevents loosening of the stack in service and consequent failure.

(a) Loosen lock nuts C. C - I and C-2. Tum adjusting screw D - I clockwise until clearance between contacts G and His between 002'and. 003 * as measured with a feeler gauge. Lock nut C - I should be drawn up firmly before this measurement is taken. Adjust C-2 similarly so that the clearance between contacts E and F is between 004 " and. 006 " with the lock nut (C - 2). drawn up firmly. This adjustment sets the interrupter section for correct operation.

(7) Turn the adjusting screw (B - 1). until the clearance between contacta G and H is between. 009'and 012 ". Adjust screw B - 2 until the clearance between E and F is between 011 " and. 013 ". This sets the rectifier section in an approximately correct position for operation.

(o) If test equipment is available it is very advisable to inspect the operation of the Elkonode before assembling into the receiver. (A suitable test circuit ia outlined later in this section) The unit should start operating at 4.4 volts (2 cells of 6 - volt battery on charge), should provide current output at 6.6 volts, and should operate satisfactorily at 8.8 volts both with load and at no load,

(t) Should the unit flare or spark excessively at higher voltages, adjust the rectifier contacts slightly to control this arcing. The contacto E and F should always have slightly wider clearance between them than contacts C and H.

(u) Do nol adjust the interrupler contacts, unless the unit will not start at
4.4 volts. Then adjust the B - 2 xrew only and do not make the clearance any smaller than is absolutely necessary. After any adjustment changes, always check the operation thoroughly at all voltages.

CAUTION (v) Do not attempt to bend contact springs.
Use only Rosin Core Solder. Keep moisture from all parts of the Elkonode. Exercise extreme care to keep metallic particles out of Elkanode. Keep dust, grease and liquid from the contact surfaces. Clean with a clean, dry piece of linen paper.

(w) When inserting the Elkonode into the rubber sock, be very careful to turn the frame of the Elkonode parallel with the Aat " sides of the inside holes of the sock, so as to leave the air spaces at the open sides of the Elkonode. The tail of the reed should be pointing toward the narrower of the two slots in the outer surface of the rubber. Bring the two rectifier leado (smaller wire) down the smaller slot and the three interrupter and ground leads dowri the larger alot, One

interrupter and one rectifier lead will have to be reversed to do this and enough slack must be left at the bend to prevent wire breakage at the soldered joint. Draw the remaining wires under the lid and fold down, seeing that the wires are pot twisted in the slots.

(2) See that the rubber pad is in the can, insert assembly with the large slot adjacent to the sam of the can and screw the lid to the can with the screws provided.

The translormer should be the same as used in the set from which the Elkonode was taken. The set may be used for test if an extension cable is made up. Do not expect quiet operation while the set is open and unit is uncanned.

1. High resistance volt-meter. Scale: 0 to 300 and 0 to 600.
Resistance: Not less than 1000 ohro at 2 volta.
2. A good quality milliammeter. Scale 0 to 50 and 0 to 100.
3. One set feeler gauges.
4. One small screw driver and one large screw driver,
5. Ono pair thin long-nosed pliers.
6. One medium-sized arbor press.

Explanation of Descriptive Letters Used to identify Special Types of Mallory - Elkon "B" Eliminators

The Mallory.Elkon "B" Eliminator is supplied in two basic types Standard (no descriptive letter) and the "C" type. The standard unit is designed for receivers which employ a floating B minus circuit (B minus not grounded) and with a voltage divider composed of a 75,000 ohm, 14 watt carbon type resistor between B minus and BM and A 25,000 ohm 2 watt carbon type resistor between BM and B plus. The "C" type is designed for receivers having the B minus grounded and where only one high voltage lead is used. Therefore, no voltage divider is used in the "C" type, except in special cases where the Eliminator is built to be used with a particular type of radio set as shown below in PC - CA and CD:

Type PC - Basic type " C. " 50.000 ohm watt carbon type resistor between B plug and BM: 50,000 ohm | watt carbon type resistor between BM and B minus. Type CA - Basic type " C. " 1500 ohm 3 watt wire wound resistor between B plus and BM. Connect wire from B plus Choke to BM terminal instead of to B plus terminal. Type CD - Basic type " C. " 25,000 ohm 1 watt carbon type resistor between B plus and BM: 75,000 ohm 1 watt carbon type resistor between BM and B minus; 1850 ohm wire wound 3 watt resistor between B plus terminal and radio frequency Choke (B plus). Type P - Standard basic type. 50,000 ohm 1 watt carbon type resistor between B plus and BM; 50,000 ohm 1 watt carbon type resistor between BM and B minus,

Type M - Standard basic type. Remove resistors between B plus and BM, and BM and B minus. Install 1250 ohm 1 watt resistor between B minus and G terminal. (It is necessary to provide screw for the G terminal point on terminal board.)

Type S - Standard basic type. Use 20,000 ohm / watt resistor between B plus and BM. Install 20,000 ohm 1/2 watt resistor from BM to G terminal. Install 5000 ohm 1 watt resistor from G terminal to B minus.

Type ST - Standard basic type. Install 20.000 ohm 1/2 watt resistor between B plus and BM. Install 20.000 ohm 12 watt resistor between BM and G terminal. Install 3500 ohm 1 watt resistor between B minus and G terminal.