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Philco 71b Filter Condenser Bank Question - Printable Version

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Philco 71b Filter Condenser Bank Question - Philco281989 - 05-02-2013

Hi guys, It has been a while since I have posted here on the site, I had moved down to Arkansas this past December and am finally getting settled in with my job and my new apartment. I just made a trip two weeks ago to Ohio and back to finally get my radio stuff. My last project was that 38-93 tombstone I finished back during the spring, which turned out great, I gave the radio to my uncle and he really enjoys it.

My next set, and forth radio project, is this 71B Cathedral I picked up at the Michigan Radio club meet last summer. I already have a few questions for you all that know about this model or have worked on one.

I have looked at the parts list and have noticed that on the list it shows each electrolytic can as 6 mfd 50-60 cycles, but below it, after the values for the twin speaker model (I have the single speaker) it shows 8 mfd 25-60 cycles. Does each can have both a 6 and 8 mfd? I only see one lead coming out of the original terminal (that has been disconnected). Also what would the voltage rating for each electrolytic and what does the cycles part mean? I am quite confused about this. Also there are two metal filter blocks in this radio, the parts list mentions one, but the other *Part No. 3583* is not in the diagram, I know this is a original part. I don't know the capacitor values in this box.

I am working on getting a parts list.

Any Help would be greatly appreciated.

Thanks

Jon

RE: Philco 71b Filter Condenser Bank Question - Arran - 05-02-2013

The 8 mf capacitor is the value of filter used in sets designed to operate from a 25 cycle AC mains power line. If your set is a 60 cycle set it used the 6mf filter cap. Point fact you could use either, but the 25 cycle model needed the extra capacity to deal with the extra AC ripple one would get from the 25 cycle mains.
Regards
Arran

RE: Philco 71b Filter Condenser Bank Question - Geoff - 05-02-2013

Quote:Also there are two metal filter blocks in this radio, the parts list mentions one, but the other *Part No. 3583* is not in the diagram, I know this is a original part. I don't know the capacitor values in this box.

Here is the information for Philco P/n 3583.

The other condenser bank is listed as P/N 05324 in the information I have. The information for that is also attached.

- Geoff

RE: Philco 71b Filter Condenser Bank Question - Philco281989 - 05-02-2013

Arran thanks for your help, I looked at the original sticker and it does say 50-60 cycles. If I understand you correctly, since this set is a 50-60 cycle set, then I will only go with two 6 MFD electrolytics, one for each can?

RE: Philco 71b Filter Condenser Bank Question - Philco281989 - 05-02-2013

Thank you very much Geoff, that answers my question. It would make sense that there is one .5 MFD since there is one wire coming out of that metal filter block. I also looked on "Philco Repair Bench" and noticed that this part number is also listed, but states 2 under number of papers, does this mean there are two .5's or just one? Thanks.

Jon

RE: Philco 71b Filter Condenser Bank Question - Philco281989 - 05-02-2013

Also am yet again puzzled, and still a novice at radio restoration and troubleshooting. I tested all the tubes, this model uses a 42 for audio output, the st type already in the chassis tested bad and quite weak. I only have several Globe type 42's in my stock. It tested good, and I will use it as a replacement for the initial power-up. I first put the set in series with a dim bulb tester just to see if the transformer has any shorts and it didn't as I expected. I did tune the dial to see if I would get anything but didn't, most likely because of the voltage limiter caused by the bulb. I then did a slow power-up with the power cord plugged into a variac. The end result was; all tubes had a glow, there was also a 60 cycle hum heard when I increased the volume pot, it went away when the volume was at zero.

The most concerning thing is that I did not get any other type of noise out the set for those 3 minutes. I am hoping that a full recap of the electrolytics and caps will fix the problem, this is my first encounter with no noise from the speaker on an initial power up.

I also noticed the mica trimmers that come off each section of the three gang available capacitor are still present, but the second one is chipped a bit and the third one is bent up on one side as in the picture. I know there could be quite a few factors contributing but, could this of caused the silence in the set?

RE: Philco 71b Filter Condenser Bank Question - Mondial - 05-02-2013

Before you start digging into the caps, you might check the RF coils for continuity. It sounds like you might have an open winding. If you are hearing no signals at all, the oscillator coil is what I would check first, then the IF transformer windings and finally the RF interstage and antenna coils.

Open coil windings are common on these sets.

RE: Philco 71b Filter Condenser Bank Question - morzh - 05-02-2013

trimmer caps causing full silence.....I doubt it. A chip in the insulator is OK, and a bent cap can be straightened out. Just try not to break the mica.

RE: Philco 71b Filter Condenser Bank Question - codefox1 - 05-03-2013

So long as the trimmer cap is not shorting out the corresponding section of the variable capacitor you're probably OK. If you decide to take them apart to clean up, count exactly the turns and fraction of turns needed to close completely, then reassemble, tighten down, and back off to get where you started from. The mica is very very fragile!

RE: Philco 71b Filter Condenser Bank Question - Geoff - 05-03-2013

Quote:I also looked on "Philco Repair Bench" and noticed that this part number is also listed, but states 2 under number of papers, does this mean there are two .5's or just one?

I checked that site too:

http://www.philcorepairbench.com/metalcap.htm

Have no idea what 2 papers means but I do know it is just one 0.5 uF capacitor for P/N 3583.

- Geoff

RE: Philco 71b Filter Condenser Bank Question - Philco281989 - 05-03-2013

Thanks Geoff, I will take your word for it, thanks once again for checking for me. I about have a parts list complete, but before I go any further, I will check the coils as Mondial mentioned, it would make perfect since to check each of the coils since this could be the root of the problem. Also thank you all for the help with the trimmer cap problem.

Now I have another question for you all, I have never really checked a coil before, I know each have corresponding terminals coming out the bottom and I know we are checking for continuity, but I don't have any type of diagram for these coils. Should I just check each terminal with the other on each coil for continuity or is there a diagram that Philco had for these sets?

Thanks

Jon

Help on checking the coils - Philco281989 - 05-03-2013

Also I looked in some of my antique reference books, and one of the books, which is a great reference is "Case histories" of Receiver Troubles and their Remedies, copyright 1939.

Under Philco 71B the book mentions a common "Case history" with this model, it reads: "Intermittent Reception" Intermittently defective condenser No. 3. I also found the same thing on "Philco Repair Bench"

http://www.philcorepairbench.com/pdf/2-125.pdf

What does this mean exactly?

I also did check the two terminals coming off the Detector transformer (coil) and I got a continuity reading of 2.37 and a Ohm reading of 24.3 k Ohms. Let me know if any of you have any data to check these coil values to those of a schematic or other published data.

Thanks

Jon