The Fine Things are Always Hand Made
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!
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 ;)
C71 & 72 should be good at 50v. Do the old caps show anything on the case?
The original cans are, with one exception, illegible. I do not trust the replacements to be correct. Thanks for the info. Anyone else?
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
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?