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1000 V Capacitors in 41-250 - Printable Version

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+--- Thread: 1000 V Capacitors in 41-250 (/showthread.php?tid=639)


1000 V Capacitors in 41-250 - Raleigh - 05-06-2007

I'm ordering parts to recap a model 41-250. Three of the .003 microfarad caps are labeled 1000 VDC. These caps seem to be bypass caps in the plate circuits of the 1st audio tube and the push-pull output tubes.

Do these really need to be 1000 volt caps? I'm just a beginner at this, but I've not run across this before.

Edited to add: I did a quick search and found this topic has been asked and answered before. The caps I have are definately Philco -- probably originals (P/N 30-4469 S.)

I guess this means I'll order the 1000 V replacements....

- Ron Ramirez - 05-13-2007

If you don't drive your radio at high volume levels, you can get by with the 630V caps in these positions. But it is a good idea to go ahead and use the 1KV (1000 V) rated caps as replacements.

Re: 1000 V Capacitors in 41-250 - OldJack1969 - 12-08-2011

I just got a unit like this Model 41-280, where can I get capacitors! I can't find the .003 1000 Volt, and what type should I be looking for to replace these wax paper capacitors. Film Axial ? I really need help with this project.
Also, I lose volume when I use both #41 tubes, but works with just one tube, sounds better but not at full strength.
Anyone with this experience?

Re: 1000 V Capacitors in 41-250 - exray - 12-08-2011

Its not necessarily the high volume levels that get ya. A static crash from nearby storms unimpeded by AVC can create quite an audio voltage pulse momentarily and the "kickback" voltage from the audio transformer can soar. I've never had a 630v yellow-cap fail in such an instance but it would be bad form to suggest that as the way to go. If the cap shorts it may take out the output transformer, field coil, etc.
Smart money says overrate the cap. It can't hurt!

Re: 1000 V Capacitors in 41-250 - Ron Ramirez - 12-09-2011

OldJack, to answer your questions, one vendor that carries 1000 volt axial metalized film caps is Just Radios. A bit of searching on the web will probably turn up a few others.

As for your loss of volume, could be a bad audio output transformer, or possibly a defective 41. Or both. Testing the tubes and performing a resistance check of the audio output transformer primary with the set unplugged is the only way to find out.

Re: 1000 V Capacitors in 41-250 - codefox1 - 12-10-2011

Don't really know how often you would need above 630 v in an AA5. Different story with caps to curb power ringing ringing or high frequency oscillations on large tube amps without optimal lead dressing, especially home brews. 2.2 KV values are often needed and used here. Been there.

Never ever hurts to use a higher voltage cap. You can always put a couple of identical caps in series (half the capacitance of each, twice the voltage, if you have the space.

Re: 1000 V Capacitors in 41-250 - Texasrocker - 12-10-2011

I just finished a full electronic restoration, full recap, and complete rewiring of a Philco 41-280 chassis. It is very similar in my Riders schematics to other similar Philco models of the same year. Didn't find any original Philco wax caps in the chassis rated a 1 KV, period. It is working fine. Sometimes, manufacturers threw in what caps they had available onhand at the assembly line. 630 volt types caps should be fine in both models. Did my Riders schematic miss something? From past experience restoring hundreds of similar circuits, I didn't see anything in the 41-280 chassis that using 630 volt type caps for coupling or bypass would not handle. Just sayin'! The faulty parts in these type sets are the original Band Switches, always worn out! Deoxit & WD-40 can only do so much to restore these type old Philco bandswitch's for sure on these particular models! Been there, done that many times before. Icon_thumbup

Re: 1000 V Capacitors in 41-250 - Marsupial - 12-10-2011

there was one like that in my 47-1230


I got a replacement from radiodaze if I remember well.

Re: 1000 V Capacitors in 41-250 - exray - 12-10-2011

Texasrocker Wrote:I just finished a full electronic restoration, full recap, and complete rewiring of a Philco 41-280 chassis. It is very similar in my Riders schematics to other similar Philco models of the same year. Didn't find any original Philco wax caps in the chassis rated a 1 KV, period. It is working fine.

Hi Randal.
Apples and oranges. On the -280 there is no plate bypassing to ground like in the -250.