The PHILCO Phorum

Full Version: 1941 Ford car Philco model F-1841
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Working on a Philco car radio model F-1841, I have been able to work through some of the issues, but I need to know where to hook up my signal generator to align it. Which pin to what tube, it appears my audio stage is working as I do have noise coming through the speaker, some crackling when I move switches. I'm not getting any radio signals. Unless there is something else I am missing I sometimes get to a certain point then I get stuck. The instructions I do have are not clear or very good for that matter as far as my paperwork is concerned.
> I need to know where to hook up my signal generator to align it. 
Pin 6 of the 7A8 to align the 455KC IF
Ant connection for the rf and osc adjustments.
To check the audio circuits use the 400cy tone output from your generator connected to pin 6 of the 7C5 (output) and pin 3 of the 7B6 (1st audio stage).

Thanks Terry, I will give it a try this evening when I get home, hopefully I can bring this thing back to life. If I have any more questions or more than likely confusions I'll let you know what happens.
Terry, so here is what I found last night, it appears it is working very surprisingly considering the condition this thing was in. So I went to the first audio stage, tone came through clear, went to the output, nothing. I thought that this was strange so I went to the 7B8 for the 455KC and that was working as I had a tone coming through that. The alignment is off just a little so I will need to adjust accordingly. But the problem with the output wasn't with the tube, but with the volume control, it is still very dirty. I've sprayed WD40 in it but it's not clean enough yet any suggestions? Also I haven't been able to figure out how to go from the 5 channel station selector to manual tuning it appears to be stuck on the selector but I would prefer to manually tune, have any idea what controls that at all?
So I was able to align the unit, that helped it out a lot, and I was able to figure out how to get it into the manual tune mode. I need to know how to deal with cleaning the pot for the volume control, and tone control, neither work well at all. The tone control doesn't work at all, and it is a slider type, and the volume pot either won't control the volume or let sound come through at all.
More than likely the volume control is worn out and needs to be replaced. Inside it has a carbon track eventually the carbon on the track wears off from usage. You can measure it's resistance from end to end, should see abt 350,000 ohms (350K). Then using an analog meter (easier to watch the needle than the numbers jump around on a digital) connected to one end and the center connection. What you should see is a smooth transition from 0 ohms to 350K. If the readings are jumping around it indicates that it's carbon trace is worn/broken. Your particular control has 4 connections. The one that is off to the side is a tap used for tone compensation. This makes it a little more difficult/expensive to find a replacement. You can do the same tests on the tone control just it's 100,000 ohms or 100K.

I did check the volume control last night and it is for sure shot, I don't get the 350k resistance through it at all, it reads 0. Through the sweeper it reads everywhere high and low. Is there a place I would be able to source a new on from, or is it going to be a hard one to find?
Try Mark Oppat at

He can supply a replacement for just about any control.
So Mark did have the exact replacement control I needed, I have the control and have now installed it, but now I have absolutely no sound at all. Not even a crackel from the speaker. Any tests I can perform to figure out whats wrong now?
Well have a look to see if you have it wired correctly.
I had to turn my phone upside down to make the drawing match the switch and it's hooked up exactly the way you have it drawn. 22k resistor in line with a .01 capacitor to ground. The wipe meets with the .004 capacitor. The final connection meets with the 1 meg resistor. Just scratching my head as it was kind of working before I replaced the control.
Ok so back to troubleshooting 101.
Got a good strong 6vdc source to power it with?
tubes lit up?
Is the spkr plugged in /connected?
Check for HV dc at pin 2 of the 41 tube?
If so remove the grid cap lead from the 75 and touch
the cap on the tube. Should buzz loud.
Power source is in good shape, I had just recharged the battery. One side of the speaker is hooked to ground, the other on the audio output side of the transformer. I think the tubes we need to look at is the 7C5, and 7B6 right? Which pin should have HV on the 7C5, and which pin would I touch on the 7B6?
Sorry had an older set on the brain.
Still pin 2 of the output tube.
Pin 3 of the 7B6
I'm not sure where the HV is supposed to be but my meters read 296 volts DC if that's the right. And nothing happens on pin 3 of the 7B6.
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