Electronic Corp. of America 108 Schematic

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Product Information:
Model:108
Manufacturer:Electronic Corp. of America (ECA)

Schematics Content:

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cob 4 .> :_

ELECTRONIC CORP. OF AMERICA

Rider

Page 2:

Page 15.-8 ECA. _
MODEL 108 '

ELECTRONIC coRP oF AMERICA

ln order to make a proper alignment, the following equipment is required:

I. A signal generator Capable of providing a modulated radio
frequency output over the frequencies required.

2, A suitable output meter or sensitive AC voltmeter with a .l
mfd series blocking Condenser.

5, A Coupling loop, made of three turns of stiff hookup wire,
4 inches in diameter, mounted on a suitable block of wood

f With the receiver on and the volume Control at maximum, connect the signal'
generator to the coupling loop and bring the loop close to the receiver chassis.
I Adjust the signal generator output to minimum necessary to give a suitable in-
dication on the output meter, which should be connected from B minus to the

l plate>of one output tube. CAUTION: Make sure the output meter islisolated

from DC by a series blocking condenser.

With the gang Condenser fully meshed, adjust the pointer so that the lett
hand edge of the pointer saddle is one inch from the end of the dial frame.
(See Dial Installation drawing) Using the dial scale contained in this Service
Bulletin, align the pointer to the indicated reference mark with the pointer
set as above. Then proceed with the alignment in accordance with the chart

SET SIGNAL SET LOOP ADJUST TUNE 4
GENERATOR AT GANG DWSTANCE TRIMMER FOR OPERATION
455 KC Meshed Close 9a Max. Align - i.F.

' J _ lob

`l720 KC ' Fully Open Close f 20a Mak. Align Oscillator

(C)John F. Rider

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ELECTRONIC CORP. OF AMERICA

Replacement of Dial Drive Cord

Completely remove remainder of defective dial cord. Inspect all pulleys
and make sure they revolve freely. Determine that no grease or oil is present
on any pulley surface. Attach the cord spring, part #A-AOEBQ, to one end of
the drive cord. 'Fully mesh the gang condenser and hook the spring to the hole
closest to the cord cutout on the'dia| drum. Proceed to string dial cord in
accordance with the detail drawing. Take two full turns around the drive drum,
part #A-HQT72. Pull the cord snug at this point. Wrap one complete turn i
around gang drum and pull cord Snug. Securely tie free end of cord to the
cord Spring. INext, adjust spring tension by moving the hook end of the spring
into the next spring hole.

Clip the pointer on to the dial cord with sufficient tension so as to
prevent slippage and adjust pointer position, so that with fully meshed gang,
the left edge of the pointer sad-
dle is one inch from the edge of
the dial support frame. insert
chassis in cabinet and check
pointer and scale agreement. Then
make final adjustment of pointer
position. Remove the chassis and
firmly crimp the pointer prongs
on the dial cord, and secure withY
a small drop of speaker cement. l

Replacement of Audio Output
Transformers

When replacing the Audio out-
put transformer, original lead
dress must be maintained. if ei- I
ther primary or secondary windings
are reversed, the set will have a
a severe audio oscillation, due to
the inverse feedback network.

Replacement of |.F. Transformers

When replacing intermediate frequency transformers, either input or out-
put, use caution to observe original lead dress.

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MODEL 108
ELECTRONIC CORP. OF AMERICA
Service Parts Llst
No. PART NAME PART No. No. PART NAME
1 Loop Antenna c-zo-szz' 30 Resistor,Fixed, 18K ohm. 1/ll w..10$
2 speaker s-QL-tosE' 31 ' ' 22K ' 1/ll w.
a oscillator Coil , S-LR-xzo' 32 " ' 100K ' 1/11 wumi
9 Input l.F. Transforner S-LR-127' 33 " ' 220K ' 1/u w.
10 output |.F. Transformer S-LR-1za' an ' ' ll7oK ' ilu w..10$
11 Output Transformer S-TA-116' 36 ' ' 2.2 "Eg-
12 Electrolytic condenser s-cE-lzeM' 37 Pilot Bulb. c.?., 3 w., 110 v.
111 " " 250 nmf. CM-an cabinet. Bake ite
15 " Paper. .002 mf., uoo v. cP-122E Knob Assembiy
16 ' ' .02 m . CP-1OME Dial Scale
17 " " .05 mf. cP-105E Pointer _
1B ' " .05 mf., 200 v. cP-1050 Dia] cord Spring
19 _' " .2 nr.. zoo v. cP-1330 Tuning snaf
20 Variable capacitor and Drum 3-20-500' 'Q' washer
21 on-off 5w|tch S~SR-137' Dial Cord Bushlng
ZZ vol.Control, Tone Control, 500K ohne S-RV-17u-1' Pilot nght Socket
23 Resistor, Fixed, u7K ohm. ilu w. 125-1368 Dial Background Plate
2" " ' " 33 " l/u w. its-2208 Loo spacer Block
25 " " 82 " l. W.. 10! RS-ZZLD Fel Knob washers
26 ' ' 100 ' 1/u w. RS~11uB Dial and Speaker Support
27 ' " 1500 " 1/2 w.,10% RS-1950 5 Lug Terminal Pane
28 ' ' 1500 " 2 w., 105 RS-195E Line Cord and Plug

Note: All items followed by an asterisk (') will be stocked by the Electronic corporation of Anerica.
' All unmarked itens nay be replaced by any nigh quality component of equal electrical value.

All DC voltage measurements in this Service Bulletin have been made with.
a 20,000 ohms per volt voltmeter, using B minus as a common reference point.
with lOOO ohms per volt voltmeter.

All AC voltage measurements are
age was maintained at l|7 volts
gang should be fully meshed and
Voltages may vary t|0% from the

Measurements of oscillator grid bias voltage should be made with a 50,000
and the ~pos it ive

ohm resistor in series with the

prod connected to B minus.
plete range with the meter connected.

(C)John I. Rider

for all voltage measurements.
the volume control at
indicated nominal value.

negative probe of the meter,

Rotate the tuning condenser throughout
Absence of bias voltage at any point
indication that the oscillator is not functioning.

SPEAKER . . . . . . .
POWER OUTPUT . . . .

its

. Plastic, Walnut Finish

iFREQUENCY RANGE . , . 540 t0 |720 KC

VPOWER INPUT . . . . . llO to |25 V. AC-DC
g POWER CONSUMPTION . . 60 Watts

Built-in Loop
Alnico V PM Dynamic 6"
3.2 ohms at 400 Cycles
5 watts Undlstorted

Line volt-
The condenser
its minimum point.

PART N0.

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