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680
RICHARDSON'S BLUEBOOK OF PROJECTION
14.
To Determine the Cause and Correction of NO SOUND DUE TO AMPLIFIER FAILURE
NOTE A: If any trouble has i/ivolved burning out of a part, even of a fuse, check for high line voltage; if this exists, no repair is permanent until voltage correction has been made.
NOTE B: If replacement is necessary per Test No. 39, do not install the new transformer until all its circuits have been checked to make sure no unsuspected short remains.
WARNING: AMPLIFIER VOLTAGES ARE DANGEROUS. When prescribed tests can be made with the amplifier turned off, bleed off the remaining high voltage charges of the filter condensers with a wooden-handled screwdriver or other well insulated conductor, before any work is done. Where tests must be made with the amplifier turned on, use only test prods and cords insulated for a thousand volts, and handle them carefully.
THE TROUBLE TESTS
THE CONDITION FOUND
NEXT
TEST
•
•
•
1.
Observe plate current meter
Reading normal
No.
2
No reading
No.
7
Very low reading
No.
10
No plate current meter
No.
12
2.
Operate plate current meter
All readings normal
No.
3
switch to take all possible
One or more readings xero
No.
14
readings
or very low
No plate current meter
No.
12
switch
3.
Apply test phones across
Sound heard
No.
4
resistor or transformer load
No sound heard
No.
18
of first amplifying tube
Level at first tube output known to be too low to operate headphones
No.
22
4.
Apply test phones across
Sound heard
No.
5
resistor or transformer load
No sound heard
No.
20
of second amplifying tube
5.
Apply test phones succes
Sound heard on each test
No.
6
sively across resistor or
No sound heard on one test
No.
24
transformer loads of re
maining amplifier tubes
6.
Investigate ouiput circuit for open or short
TROUBLE FOUND