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Philco 60B Capacitor Question - Printable Version

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RE: Philco 60B Capacitor Question - Jamie - 10-25-2013

Brenda, for what it's worth, my suspicion is that one of the wires from the voice coil was shorting to the chassis of the speaker. I don't know if that could cause an electrolytic cap to overheat like that. At the same time I unhooked that .05 cap, I also moved those speaker wires away from the speaker chassis. I am interested in yours and Mondials opinion on this, as I would like to know too.

RE: Philco 60B Capacitor Question - Mondial - 10-25-2013

It is very unlikely that the voice coil wires have anything to do with the power supply problem. The voice coil is isolated by the output transformer, and grounding of the wires to the frame, or chassis for that matter should make no difference.

As far as Brenda's question, a lot depends on what is actually wrong with the .05 cap. It is connected from the B+ line to ground, yet it did not show a short or significant resistance when the rectifier filament pins were checked to ground with an ohmmeter. This cap should just be an RF bypass, and the set seems to work without it, so it really is a mystery. Possibly the cap breaks down and arcs internally when the voltage reaches some critical level?

We really are not sure if the cap is actually at fault, so you might connect the cap back temporarily and turn up the variac just enough to see if the filter cap gets warm at all. That would confirm it once and for all that the .05 cap was the problem.

RE: Philco 60B Capacitor Question - Jamie - 10-25-2013

I'll do that tomorrow, as soon as I get home from Lexington. I'll check in then.

RE: Philco 60B Capacitor Question - Jamie - 10-28-2013

I finally got some time to work on this today. I temporarily connected the disconnected cap, powered up the set and no problem. No heat at all. Like I said in a previous post, the only other thing that had been touched were the wires coming to and from the voice coil. Other than that, I followed instructions to a tee. I have since restuffed all the bakelite caps. I plan to restuff the metal condenser bank today, then replace resistors.

RE: Philco 60B Capacitor Question - Chuck Schwark - 10-28-2013

The wires you moved away from the chassis edge were most likely the FIELD coil wires carrying the B+ voltage and not the voice coil wires.

As a further precaution, I would carefully check for cuts/wear in the insulation and slip sone heat-shrink on the those wires to be sure there is no future chance of another short in that area.

Chuck

RE: Philco 60B Capacitor Question - Jamie - 10-28-2013

Thanks Chuck. I moved them all, but the voice coil wires were the only ones that looked sketchy. The field coil wires could have been shorting though... I will insulate them all before this chassis is finished.

As of right now, I cannot get it to play. I get low volume static from the speaker and that's it. If I touch the middle lug of the volume control, or either of the grid caps, I get loud static. If I touch one the pins on the 42 or 75 tube (using the dmm), it plays a station, but it is not tunable. I've gone through it as far as my knowledge will take me. All caps are replaced, and out of spec resistors are replaced. Tubes are good, band switch is cleaned up.

Plate voltages are high. but not extremely out of line (at least I don't think).. I can post them if need be.
Once more, I turn to you guys... Any help would be appreciated... I am not good at chassis work, so I'm sure I missed something..

RE: Philco 60B Capacitor Question - Mondial - 10-28-2013

Sounds like the local oscillator of the 6A7 converter tube is not working. Might be an open oscillator coil.

You can place a transistor radio close to the chassis and listen 465 KHz above the dialed freq. You should hear a carrier as you tune the model 60 tuning dial slightly.

Do you have a signal generator which can give you a signal at the IF freq to see if the IF stage is working? If you can inject a IF signal into the 6A7 grid cap you sould be able to hear it loudly in the speaker if the IF is working.

You can also check all the coil windings for continuity.

RE: Philco 60B Capacitor Question - Jamie - 10-28-2013

I used a signal generator to inject a signal at the grid cap of the 6A7. It came through loud and clear.

I am trying to check the oscillator coil. If I am looking at the right part, it has five lugs coming off an open cylinder?... I've got continuity on 4 of them. I can also post ohm readings if need be.

BTW - I found the cause of the overheating cap. I put the old 80 tube back in the chassis. The cap exploded. Puhpow. Plate to filament short.

RE: Philco 60B Capacitor Question - Jamie - 10-29-2013

Does anyone have a link to instructions on how to check and, if need be, repair the oscillator coil? I'm about out of patience with this radio.

RE: Philco 60B Capacitor Question - Chuck Schwark - 10-29-2013

Ah, you doubt me Grasshopper? Icon_wink

Here on my site: http://www.philcorepairbench.com/tips/svctip36.htm

Equally applies to osc coils too.

Chuck

RE: Philco 60B Capacitor Question - Jamie - 10-29-2013

Thanks Chuck! .. I'll give it a shot. There are five lugs on my coil and I'm not sure if they should all have continuity or exactly how it's put together.

RE: Philco 60B Capacitor Question - Chuck Schwark - 10-29-2013

Tracing the schematic and how it's wired to the other components will tell you "who's who" on the windings.

Chuck

RE: Philco 60B Capacitor Question - Bob Andersen - 10-29-2013

Don't give up. It's a rare 60 that doesn't have an open oscillator coil. There are some hand drawn diagrams in the ARF thread that might be helpful: http://www.antiqueradios.com/forums/viewtopic.php?p=1289038

RE: Philco 60B Capacitor Question - Jamie - 10-29-2013

Thanks Bob! That link is exactly what I needed. Between that and the info Chuck provided, I should be able to figure it out. I'll let you know how it goes.

RE: Philco 60B Capacitor Question - Jamie - 11-03-2013

Mondial you are a genius! .... Chuck and Bob, thank you guys so much for those links!!!... I actually did it! I can't believe it. I rewound that coil and the whole time I am thinking "there is no way that I did this right", "I've really screwed this up".. I've never rewound a coil before. Lo and behold, I fired it up and it works!!!!

I sure can't believe it!... Thanks so much!