Philco 66 - Sweet Music at Last!! - Printable Version
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RE: Philco 66 -Nothing - jph14 - 04-30-2012
Center tap straightened out. G1 on 42 tube -16v. Other voltages now much better. Still low on 75 tube.
Will check everything at vol. control. Should there be any voltage here? If so, what should it be?
Thanks,
Joe
RE: Philco 66 -Nothing - rghines1 - 04-30-2012
The low voltage on the 75 tube may not be a concern. Check R28 and R29 anyway for large increase in resistance. Would expect a bias on G1 of the 75 tube's triode to be between -1 to -2 volts.
Should hear a loud hum when the finger touches the wiper of the volume control. Any DC voltage on the volume control is negative by a few volts from AVC action.
No mention of the oscillator. Normally should see -5 volts on G1 of the 6A7 tube if it is running.
Good you got the 42 tube bias circuit straighten out.
RE: Philco 66 -Nothing - jph14 - 04-30-2012
R28 and R29 OK. G1 of 75 a little over -1v. Do not get a loud hum on vol. control. G1 of 6A7 -3.3v.
Osc. coil? How do I check this and what is the repair?
This is pushing my limits of current ability. Will continue with all the advice.
Thanks!
Joe
RE: Philco 66 -Nothing - rghines1 - 04-30-2012
With -3.3 volts on the 6A7 that tells me the oscillator is OK. Probably getting some capacitive loading from your meter not allowing more than -5 volts.
Does you signal generator have a separate audio output tone? Looks like we are down injecting a signal on the 75 and 42 tubes' G1 grids.
RE: Philco 66 -Nothing - jph14 - 05-01-2012
My signal gen. does have an audio output- never used it.
Interesting happening last night. While tuning trimmers to 460 I got good volume and went to wave trap and made adjustment. I had my signal tracer out and on and picked a channel through the tracer. It was a rather strong station here at 640. I had ant. hooked up to radio at the time and the probe was very close- the channel got louder when I touched the ant. connection. Don't know if this means anything.
Thanks,
Joe
RE: Philco 66 -Nothing - morzh - 05-01-2012
If your antenna is not strong enough, you will see the increase of volume when touching it - you become an antenna yourself.
RE: Philco 66 -Nothing - jph14 - 05-01-2012
(05-01-2012, 03:20 PM)morzh Wrote: If your antenna is not strong enough, you will see the increase of volume when touching it - you become an antenna yourself.
Touched with the probe.
RE: Philco 66 -Nothing - morzh - 05-01-2012
Does not matter. I touched mine with a Fluke meter's probe and it screamed.
RE: Philco 66 -Nothing - jph14 - 05-03-2012
Still no luck with 66.
Rechecked everything- voltages Ok. Resoldered some old joints.
Found a resistor in the osc. trans.- part 16 on schematic- cannot find on schematic. It goes from lug 2 to 4. Value? Is this part of problem?
Also- cannot get the 4 trimmers to 460- very faint - little adjustment.
Thanks,
Joe.
RE: Philco 66 -Nothing - morzh - 05-03-2012
Which one is lug 2 or lug 4? The sch does not enumerate them.
RE: Philco 66 -Nothing - jph14 - 05-03-2012
(05-03-2012, 01:45 PM)morzh Wrote: Which one is lug 2 or lug 4? The sch does not enumerate them.
I went from mounting lug and counted left. I believe it is primary winding, but not sure.
Joe
RE: Philco 66 -Nothing - rghines1 - 05-04-2012
On the Philco 66 service info it mentions changes for Run 9, July 10th using a 70 ohm resistor in series with the oscillator coil. It fixes a problem at the end of the shortwave band.
Oscillator frequency typically runs above the incoming RF antenna signal. Therefore with the radio dial at 1000 KHz, the oscillator freq. should be 1000 + 460 giving 1460 KHz. Use another radio held near to listen for a beat signal between 1400 and 1500 to verify the oscillator is running at or near the correct frequency.
RE: Philco 66 -Nothing - jph14 - 05-05-2012
(05-04-2012, 07:37 PM)rghines1 Wrote: On the Philco 66 service info it mentions changes for Run 9, July 10th using a 70 ohm resistor in series with the oscillator coil. It fixes a problem at the end of the shortwave band.
Oscillator frequency typically runs above the incoming RF antenna signal. Therefore with the radio dial at 1000 KHz, the oscillator freq. should be 1000 + 460 giving 1460 KHz. Use another radio held near to listen for a beat signal between 1400 and 1500 to verify the oscillator is running at or near the correct frequency.
Thanks. Resistor reads 82 ohms - will replace with a fresh one.
Tried with another radio- did not hear anything between 1400 and 1500.
Joe
RE: Philco 66 - suspect coil issues - jph14 - 05-12-2012
Just ordered magnetic wire. While waiting will re-check everything I have already done. The only repairs have been to the waveband switch and the compensating condensor(#13).
Other than that only recapping and new resistors.
Thanks for everything to all those taht got me this far.
Joe
RE: Philco 66 - Coil troubles? - jerryhawthorne - 05-24-2012
Something still seems suspicious concerning the audio stage. Volume control max, touch the center tap of the volume control, you should get a loud hum. You indicated you didn't. Need a strong amp prior to alignment and further troubleshooting. Confirm please, no loud hum.
Jerry