Recapping Philly power supply

[Ted Coombes]

I finally got around to recapping my pointer-dial Philly (late '37 or early '38). I figured I'd start with the power supply -- that should be easy, right?

For reference, here's the schematic from Nostalgia Air: http://www.nostalgiaair.org/Resources/611/M0016611.htm

Mine has the diamond-shaped placement of the 'lytic cans as shown on p. 14-47 of the schematic (but most of these have been replaced below the chassis). The can 'lytics (C65 - C68) are pretty straight forward, although I might have trouble finding a 30 mf rated a 475 WVDC (of course, I have a 450 WVDC, but this is probably not the right place to scrimp since it is apparently the input filter). Maybe someone can direct me to where I can find a 30 mf 500 WVDC.

C70 is a 16 mf, 475 WVDC. Again, maybe I can find a 16 or 20 mf 500 WVDC,

The next two have me stumped. C71 is marked as a 500 mf, but no working voltage listed. C72 is listed as 50 mf, again no working voltage. And c73 is the darndest thing you ever saw -- it screws into the side of the chassis! But I should be able to find a 100 mf, 50 v substitute and cobble it in.

P. 14-47 shows two 83V rectifiers, which is what I have (actually, one of mine is a plain old 80). But p. 14-49 power supply schematic shows two 5Z3s! Of course, I'll stick to 83Vs.

Any suggestions as to where I can find the 475 (or 500) v capacitors, and what WVDC to use on C72 and C73? Thanks!

[Bill Liers]

Ted,

I see all electrolytics rated for 450 on the schematic. This is what I've used all along and never an issue. Modern electros have considerable margin built in and I doubt you will ever see these voltages. I would use caps from a mfr that has good quality control such as Sprague or Panasonic.

You can find the higher working voltage caps here in case I get beat up for suggesting substandard parts ;)

http://angela.com/spraguetvatypeatomaxialelectrolyticcapacitors.aspx

C71 & 72 should be good at 50v. Do the old caps show anything on the case?

regards, Bill

[Ted Coombes]

The original cans are, with one exception, illegible. I do not trust the replacements to be correct. Thanks for the info. Anyone else?

[David C. Poland]

Ted,

For the electrolytic caps, use modern version, and go up somewhat in value to the next available. They are smaller, and reliable if sourced from a quality source. And keep the old electrolytic cans in place for appearance sake (but disconnected, of course.)  For the 30 MFD, use 33 MFD @ 450volts, for 8 MFD use 10 MFD, and so on.  For the 16 MFD, 22 MFD is satisfactory. You may find a 100 MFD low voltage at Radio Shack but will not find the high voltage caps required of old radios there.   Mark Oppat (http://www.oldradioparts.net/testimonials.html)  or Bob Piekarz (http://www.radioantiques.com/) are good sources for caps and other parts.

As for the 83-V rectifiers, the really early pointer dial Philharmonics had them as per the early diagram, but I have never seen a pointer Philharmonic with them. Mine and others I have seen use 5Z3's,  consistent with  my owners manual.  There is an amp diagram dated 5/1/1937 showing 5Z3's just a few weeks after the Philharmonic was announced. So, look carefully at  your tube sockets to see what tube number is embossed.

- Dave P

[Ted Coombes]

I finally got a legible copy of the schematic, and after parsing it through, I've identified all the caps in the PS circuity except one. Those high-capacitance, low-voltage capacitors turned out to be be small mica-mold plastic caps, which I replaced yesterday. The caps I wasn't able to procure locally from Affiliated Electronics in Tulsa, I have on order and should receive by end of this week. I was able to obtain the 475 WVDC capacitors, thanks to the lead from Bill. And David, the rectifier sockets are indeed marked for 83-Vs. This must be a very early Philly.

There's only only one thing I haven't figured out. On the schematic page (Scott 14-47) showing the layout underneath the PS chassis, it lists a C-68 at 60 mf, 300v. The layout shows two C-67s (30 mf, 475 v) among the four vertical cans on top of the chassis, and the circuitry bears this out. But I can find no location, either on the schematic or in examination of the circuitry, of C-68. The schematic lists an identical C-65 (60 mf, 300 v with same part number as C-68), and I have located it in the circuitry. In other instances where more than one of the same capacitor is used (e.g. C-67, C-69, C-71 and C-72), a single identifier and part number is listed. That leads me to believe that inclusion of C-68 was in error; that there is, in fact, no C-68. Can anyone else find C-68?