|
Next touch tube pins marked "DP" on
the 12AV6 tube. If no signal, check or replace the following:
| 1. |
Check or replace 12AV6 tube.
|
| 2. |
Check or replace 12AV6 tube
socket. |
| 3. |
Check or replace condenser,
item 19 on circuit diagram and parts |
| |
layout. |
Now change signal generator from audio position to generate an
intermediate frequency signal. Set signal generator to 262
kilocycles, leaving .05 mfd condenser in signal generator lead to
protect the signal generator from "D.C." voltage. Keep signal
generator grounded to radio chassis.
Next touch tube pin marked "P" on 12BA6 intermediate frequency
amplifier tube. If no signal, check or replace the following:
| 1. |
Check or replace intermediate
frequency transformer, item 7 on circuit |
| |
diagram and parts layout.
|
| 2. |
Check or replace resistors,
items 39 and 41 on circuit diagram and parts |
| |
layout. |
| 3. |
Check or replace condenser,
item 19 on circuit diagram and parts |
| |
layout. |
| 4. |
Check or replace volume control
assembly, item 51B on circuit |
| |
diagram and parts layout.
|
Next touch tube pin marked "G" on 12BA6 intermediate frequency
amplifier tube. If no signal, check or replace the following:
| 1. |
Check or replace 12BA6 tube.
|
| 2. |
Check or replace 12BA6 tube
socket. |
| 3. |
Check or replace resistor, item
37 on circuit diagram and parts layout. |
Next touch tube pin marked "P" on 12BE6 tube. If no signal, check
or replace the following:
| 1. |
Check or replace intermediate
frequency transformer, item 6 on circuit |
| |
diagram and parts layout.
|
Next touch tube pin marked "G" on 12BE6 tube. If no signal, check
or replace the following:
| 1. |
Check or replace 12BE6 tube.
|
| 2. |
Check or replace 12BE6 tube
socket. |
Next change signal generator from intermediate frequency setting
to radio frequency signal, leaving the .05 mfd condenser in lead
to protect signal generator from "D.C." voltage. |
Set signal generator to 1000
kilocycles and tune radio receiver to 1000 kilocycles (100 on dial
scale).
Next touch tube pin marked "P" on 12BA6 radio frequency amplifier
tube. If no signal, check or replace the following:
| 1. |
Check or replace radio
frequency coil, item 4 on circuit diagram and |
| |
parts layout. |
| 2. |
Check or replace oscillator
coil, item 5 on circuit diagram and parts |
| |
layout. |
| 3. |
Check or replace condensers,
items 14A, 14B, 15A, 158 and 16 on |
| |
circuit diagram and parts
layout. |
| 4. |
Check or replace resistors,
items 35 and 38 on circuit diagram and |
| |
parts layout. |
Next touch tube pin marked "G" on 12BA6 radio frequency tube. If
no signal, check or replace the following:
| 1. |
Check or replace 12BA6 tube.
|
| 2. |
Check or replace 12BA6 tube
socket. |
| 3. |
Check or replace resistor, item
31 on circuit diagram and parts layout. |
Next touch antenna terminal at antenna socket. If no signal, check
or replace the following:
| 1. |
Check or replace antenna coil,
item I on circuit diagram and parts |
| |
layout. |
| 2. |
Check or replace condensers,
items 11 and 13 on circuit diagram and |
| |
parts layout. |
| 3. |
Check or replace chokes, items
2 and 3 on circuit diagram and parts |
| |
layout. |
This completes the entire checking procedure of the receiver, and
if the procedure has been followed as outlined, the failure will
have been located. After repairing failure, receiver will operate
and should now be aligned for proper performance.
PROCEDURE FOR ALIGNMENT
OF 987187 RADIO
All receivers are properly aligned at the factory and should
require no further adjustments, (except adjusting the receiver to
the antenna when installation is made), unless the adjustments
have been tampered with, or new coils, intermediate frequency
transformers, or tuning cores have been installed. |