Kodak FS-10-N Operation & Maintenance Manual page 16

SERVICING THE AMPLIFIER
(Symbols referred to are those used in the diagrams.)
~ IF _ _ F_U __ S_E_N _ _O_T _ _ B _ _ L_O_W _ _N
I I~
IF _ _ F_U_S __ E_B __ L_O_W __N _
No Sound From Film Altho Tubes Glow
1. No "background" is heard; volume control and
exciter lamp control fully advanced. "Background"
is normal to a properly operating sound projector and
is due largely to tube noises.
a. Speaker voice coil may be open. Test coil, con-
necting cord, and speaker plug (refer to loud speaker
and cord assembly diagram).
b. Remove amplifier and check:
(1) Condensers C-14 and C-15 (part No. 79826)
for shorts.
(2) Exciter Lamp Control R-17 (part No. 58426),
Resistor R-16 (part No. 78361), Condenser C-13
(with C-2 part No. 69301), Condenser C-11 (part
No. 58527), and Condenser C-16 (part No.
- - -798-2-2).
(3) Exciter Lamp Rheostat and Amplifier Switch
R-18 (part No. 78476) for continuity; also, wiring
to Exciter Lamp Socket (part No. 58343) and to
Amplifier Plug Receptacle (part No. 58337).
2. If "background" is heard. Plug in a high-impedance
microphone or phonograph pickup and listen for sound
reproduction.
a. If sound is now heard:
(1) Inspect photocell for proper position and for
good contact with spring clip. The cathode in a
normal cell has a brownish appearance; whitish
or "silvery" appearance usually indicates leakage
of air into the cell due to fine cracks in the glass
envelope or a broken seal.
(2) Inspect sound rod for breakage or misalign-
ment. See page
XIII.
b. If sound is not heard:
(1) Check grid clip on 6J7 tube for good contact.
(2) Check position of 6J7 tube in its socket.
(3) Test 6J7 tube in tube tester.
(4) Test all other tubes.
XIV
And New Fuses Blow Repeatedly
1. Test rectifier tube, oscillator, and output tubes.
2.
Check continuity of power transformer T-4 (part
No. 78335) with special attention to ,high-voltage
secondary winding.
3. Check sections C-9 and C-12 of No. 78677 Filter
Condenser Block for shorts; also check C-16 Condenser
(part No. 79822) for short.
4. Check amplifier connecting-cord wires 2, 3, 4, and
5 for short to ground. Terminals 6 and 7 will normally
show a very low reading to ground. It may be necessary
to disconnect wires 2 and 5 to distinguish between a
short in the cord and a short in condensers.
5. Check amplifier wiring generally for shorts or
broken leads.
LOW AMPLIFIER OUTPUT
1. Test all tubes. Check all amplifier voltages-refer
to amplifier voltage diagram.
2. Exciter lamp current may be low-radio frequency
thermoammeter will be required to check current.
3. Photocell voltage may be low. Accurate setting
(maximum 90 volts) requires the use of an electrical
.
.
bridge circuit. Distortion and noise will be excessive
with voltage at too high a value and photocell will
deteriorate rapidly.
4. Extra extension cord not heavy enough to carry the
load.