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Philco 37-670 restoration thread
#20

(01-26-2015, 05:28 PM)Ron Ramirez Wrote:  Let's examine your first question first. Icon_smile

The .05 uF cap, part (20), is tied into the B+ line feeding the plate of the RF tube (through the appropriate coils, of course), and it looks to me that it acts as a bypass to keep stray RF out of the B+ line.

The second question is more tricky.

1000 volts were specified due to the possibility of voltage spikes at the plates of the audio output tubes. Now, there has been disagreement among experienced collectors/restorers as to whether they really need to be 1000 volts or not. All I can tell you is that I've been using 600/630 volt caps as these plate bypasses for years, and have yet to have one blow up on me. But then again, I do not run my radios at high volume levels. If you run a radio full blast, then it *might* need the 1000 volt rating. YMMV.

Just curious...why are you using a Canadian 37-3670 schematic? Although it should be the same as the USA 37-670 schematic, I think...
Ron,

This is the only schematic I could find, apart from the NostalgiaAir one which isn't so great (honestly I did not know I had Canadian version). I have ordered paperwork from  Chuck Schwark at the Repair Bench (comes highly recommended as I'm sure you know) but haven't received it yet; just sent payment a few days ago.

Anyway, the schematic appears mostly correct; a few differences, but I have stuck to the original wiring in those cases. Thanks for the info on those .03 caps, 1000V. I'll never crank the radio, so shouldn't be an issue, esp. with running those .0068s in series. 

Thanks! Fired up the radio for the first time last night after replacing the electrolytics, AC to ground and some other caps, and got reception. What a sweet sound!
I wonder if the set ever played after the previous restoration. Among other problems, previous person wired electrolytic 86A backwards  Icon_eh he ran the negative to ground; this one has positive to ground.

Cheers, time to go hunker down for the blizzard,

Ted


Messages In This Thread
Philco 37-670 restoration thread - by Diverted - 12-30-2014, 03:55 PM
RE: Philco 37-670 rectifier - by millievolt - 12-30-2014, 04:25 PM
RE: Philco 37-670 rectifier - by Diverted - 12-30-2014, 05:03 PM
RE: Philco 37-670 rectifier - by Chuck Schwark - 12-30-2014, 04:28 PM
RE: Philco 37-670 rectifier - by millievolt - 12-30-2014, 04:33 PM
RE: Philco 37-670 rectifier - by morzh - 12-30-2014, 06:27 PM
RE: Philco 37-670 rectifier - by Diverted - 12-30-2014, 07:45 PM
RE: Philco 37-670 rectifier - by OZ4 - 12-30-2014, 08:14 PM
RE: Philco 37-670 rectifier - by Diverted - 12-30-2014, 08:35 PM
RE: Philco 37-670 rectifier - by OZ4 - 12-30-2014, 09:10 PM
RE: Philco 37-670 rectifier - by thirtiesradio - 12-31-2014, 03:44 AM
RE: Philco 37-670 rectifier - by Arran - 12-31-2014, 04:54 AM
RE: Philco 37-670 rectifier - by Diverted - 12-31-2014, 09:03 AM
RE: Philco 37-670 restoration thread - by John R - 12-31-2014, 05:19 PM
RE: Philco 37-670 restoration thread - by OZ4 - 12-31-2014, 01:03 PM
RE: Philco 37-670 restoration thread - by Diverted - 01-26-2015, 08:40 PM



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