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R-392 Troubleshooting Table


Reference: Para 97, R-392 Manual (paraphrased for brevity)

Organization: Symptom
Probable Trouble
Corrective Action
1. Function to NORMAL, Dial Dim to ON, Receiver does not operate,
dial lamp does not light.

Open LINE fuse 5 AMP, F102 on front panel

Replace fuse. If it blows again, check filament circuit
for shorts. Check power connections.
2. Dial lamps light but CARRIER LEVEL meter pointer does not
deflect w/ AGC switch set to ON, no reception.

No B+ voltage. Open PLATE fuse, 1/2 AMP, F101 on front panel.

Replace fuse. If it blows again, test B+ circuit for shorts (fig. 51)
3. No receiver output. Carrier level meter rises and dips as
KILOCYCLES control in operated.

Defect in signal circuit after 2nd IF AMP.

Connect headphones with 0.1 microfarad cap across grid and plate
circuits of successive audio stages, or use stage gain charts (par. 99)
Test tube of defective stage, check voltages and then resistance within stage.
4. AF circuits ok, but no signal output with 455 KC sig gen is applied to IF input

Faulty IF amplifier stage.

Test IF stages by signal substitution (par. 101); test tubes; localize with
voltage and resistance checks if necessary.
5. IF circuits respond to 455 KC signal, still no station received.

Faulty mixer, oscillator, or RF stage.

Test mixer, RF and oscillator states by signal substitution (par. 102)
6. No beat frequency when BFO switch is on and BFO PITCH is varied.

Faulty BFO circuit.

Test tube V604; test voltages, check BFO switch and BFO pitch control(C101) .
7. No calibration signal when AGC switch set to CAL. Cal signal does not appear
approx every 100 KC.

Defective calibration oscillator or vfo-mixer stage.

Test tubes V701, V702, V703. Test crystal Y701. Check voltages and resistances
of cal oscillator and VFO (V801).
8. Weak Signal

Weak tubes, low voltage

Test tubes; test input voltage; check B+ voltage. Check for shorted or open
capacitors, check gain of each stage. Last resort: align tuning circuits.
9. Noisy receiver.

Noisy antenna location. Poor connection or shorting elements within a tube.

Short-circuit antenna to ground, if noise reduced was external.
Check antenna and internal signal cables and connectors.
Use insulated prod to tap each tube, replace ones which generate noise with tap.
10. Receiver output noisy when controls are operated.

Dirty switch contacts, potentiometers, etc.

Clean switch contacts; clean or replace controls.
11. Distorted signal, or blocking with strong signals.

Weak tube; incorrect voltage on tube; leaky capacitors, esp C623 and
C626. No AGC voltage.

Chekc all tubes. Check AGC voltages. Check plate voltages and resistances.
12. Function switch to SQ (squelch), RF GAIN/SQUELCH THRESH at low gain setting,
noise is heard between stations/signals when KILOCYCLES control is tuned.

Faulty squelch circuit.

Check V602, V609, V 605. If a click is heard as KILOCYCLES is rotated,
check relay K601.