 | No signal - AM ,CW ,SSB or swish:
 | (1) VFO - XTL switch position. PTO out-put, XTL oscillator output, Ant. Coaxial leads. |
|
| Signals weak on 40/80 M., nearly normal on 15/10:
| (1) Check T1 for lightning damage, or RF burn out. |
|
| No reception on one band:
| (1) Band switch contacts or XTL of band. |
|
| SSB ok, AM distorted:
| (1) D-7, Q-5 |
|
| No SSB, AM OK:
| (1) C-173 |
|
| SSB distorted:
| (1) PB tuner - Knob settings, Alignment |
|
| SSB, AM distorted :
| (1) Audio amplifier. |
|
| Cathode resistor burned up R-44:
| (1) V-7 shorted. |
|
| Anti-VOX low, below 90 VAC :
| (1) V-7, audio drive to V-7 (3V or more) |
|
| Intermittent noise, not subject to mechanical shock:
| (1) C-67, C-68 |
|
| Noise when tapping chassis "S" meter drops, no solder joints or switch contacts:
| (1) (1) C-126 |
|
| Loss of sensitivity, hum on signal:
| (1) V-10 |
|
| Hum in NB position, with no signal applied:
| (1) V-10 |
|
| PTO jumps in frequency:
| (1) PTO cover loose |
| (2) D-9 zener. |
|
| Noise level raises with calibrator on:
| (1) D-9 zener. |
|
| Signal shifts frequency when calibrator is switched on:
| (1) D-9 zener. |
|
| "S" meter up scales switching from AVC off to AM:
| (1) V-4, V-5, V-9, Q-4 |
|
| "S" meter up scales after warm up
| (1) Q-4 |
|
| "S" meter cannot be set on Sl, down scales
| (1) V-3 |
|
| "S" meter up scales, zero adjust has no effect. Loss of signal strength,
maybeintermittent:
| (1) T-10 |
|
AVC TROUBLE IN R-4 and
R-4A
Injection voltage is usually .2 to .3 volts R.F. with cables
connected. If loss is decided on a particular band, retuning of injection trimmers per instruction manual is recommended.
After the unit has been on for 15 to 20 minutes AVC in slow position, remove 12BZ6 (V-l). Note if AVC falls to 1.35 volts at TP-2.
Leaving V-1 out, replace 12BE6 (V-3) with known good tube. Leave this tube in. The voltage at TP-2 should start falling towards 1.35 volts unless leakage is occurring at one or more of the following stages:
12AV6 (V-13), 12BA6 (V-4), 12BA6 (V-5).
Remove VTVM probe and zero the S-meter switch through AVC positions to off and back to slow position. The S-meter should not have moved over one half S unit. If movement was over one half S unit, substitute 12AV6 with one or more tubes until requirement is met.
Reconnect VTVM probe to TP-2, slow AVC position. Adjust R-87 for 1.35 volts. Remove probe and zero S-meter. Advance R.F. gain fully counterclockwise and adjust R-40 for 60 over S-9. Recheck S-meter zero and 1.35 volt settings.
Install new 12BZ6 and allow warm-up time. Monitor 1.35 volts at TP-2. If no change after warm-up, the AVC circuit is normal. To double check leakage of V-4 and V-5, advance S-meter zero to maximum, S-meter should read S-5 to S-8. Failure to do so indicates leakage in V-4 or V-5, or both. if these require changing, recheck S-meter zero and 1.35 volt settings.
The difference in plate current between transceive and transmitter and receive positions, at a given setting of the
gain control, is normal if the gain is set substantially less than maximum.
The receiver's premixer output is coupled to the transmitter's transceive switch, via the injection cable, when the units are
connected together.
In transmitter mode, this line is opened by the switch, and at the same time a negative voltage is sent down the injection cable, biasing the grid of the receiver premixer tube to cut-off. The premixer stage of the transmitter then drives the mixer stage of the transmitter.
When the switch is put in "Receiver" position, the premixer stage of the transmitter is biased off by the negative voltage, the premixer output of the transmitter switched out and the premixer output of the R-4 B is then coupled into the mixer stage.
In both positions, the injection cable has the premixer output on it and some loss occurs due to the loading effect of the cable.
In transceive position, the cable is switched out of the transmitter section and the loading effect is gone. Therefore, the premixer output of the transmitter rises somewhat, giving more drive in this position.
Normally, with the gain advanced to 12 o'clock or better, saturation occurs and the output of the transmitter remains nearly the same in all three positions, usually less than 30 mils of plate current.
