37-630 code 125 missing all 110 pF caps - Printable Version
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+--- Thread: 37-630 code 125 missing all 110 pF caps (/showthread.php?tid=26393)
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-02-2026
So in the process of recapping, I got to cap #61, which is a .008 mfd at the tone control, which is connected to the plate of the 6F6. Did not see that it is rated at 1000V. Philco doesn’t list voltage ratings in the parts list like Zenith did so was assuming all would be good with 630V replacements. Does this cap need to be 1000V since it will be seeing voltage spikes for the tone control changes, or will 630V work? Or could I double up a couple of .015 mfd to get the working voltage to 1260V?
RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-02-2026
You could serialize the 0.015uF.
RE: 37-630 code 125 missing all 110 pF caps - RodB - 04-03-2026
Yeah, what Mike said. Wire two of those in series. Do you plan on removing the rf chassis to replace the two paper caps buried at the top?
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-03-2026
Already got the RF section pulled from the main chassis. Will get to it after i get the main chassis done.
RE: 37-630 code 125 missing all 110 pF caps - RodB - 04-03-2026
Is there about 16 wires connecting it up?
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-04-2026
I think I counted 9.
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-05-2026
Well got the main chassis recap all finished up this afternoon, now off to the RF chassis… this should be fun…
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026
I finally got the chassis all back together and playing. It plays quite well even before the alignment. The only thing I’ve noticed is with the tone and volume control. With the tone control, the first and second positions when turned on sound the same with no change in tone when switched. The third position then cuts out the high notes. The schematic shows a weird setup though where nothing seems to be connected to the second position. Then with the volume control, it has very low volume (albeit smooth volume) until I get to what I believe so the tap on the control and then the volume increases dramatically. It’s goes from very little to booming volume instantly at one spot. Will give it a full alignment and double check my wiring. Don’t know it this has something to do with the tone control as the volume pot is connected directly to the tone switch… the only other thing is that I did add the missing 110 pF caps. Maybe the one off the volume control is pulling the volume down until it hits the tapped section and then jumps back to normal??
RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-19-2026
Measure your volume pot end to end first. See if it is what is supposed to be (1Mohm).
Then, whatever it is, put your ohmmeter to the GND and the wiper and run it from the bottom up, and see if it goes from some sensible increasing value to almosty open or very high abruptly.
RE: 37-630 code 125 missing all 110 pF caps - gary rabbitt - 04-19-2026
Hi sdradioman,
A few posts back you mention the .008uf/100V cap. (on the Factory parts sheet it is part 56). There is a reason for those caps to be rated at 1kv or more.
If there is a static crash, like from a bandswitch being changed, an close lightening (audio or sharp spike or similar audio, the tube could go into cutoff and the could cause internal flashover in the trans from the field collapsing. When the collapsing field in any trans can cause a kickback or flashover spike of high voltage for an instant, the cap rating is needed to mitigate that energy and protect the trans.
This is the same action that was used for automotive ignitions back ion the day. The opening of points, the collapsing field would cause the ignition spark.
I personally will seek out the same voltage spec, even higher, on those caps in the output rated for 1KV or more. While the 'normal'
voltage on those pints may be only a couple hundred volts, the spike Voltage for that instant can reach over a KV or more.
The late Leigh Bassett and another person made the same comment about using the higher voltage spec caps on the outputs.
Just passing this along, many of you probably know the reason as well already.
RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-19-2026
I wonder if introducing a snubber would work to simply suppress the overvoltage. Some that use resistors for dissipation require a certain power rating, but this is when used in DCDC converters where it happens every cucle wherea here it only happens sporadically and so the resistor will not dissipate all the time.
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026
That was for part number 61, a .008 @ 1000V. I put a .01 and .05 in series to get me .008 at 1200 V. Is that incorrect? Also, I removed the 110 pF cap #46 at the volume control, and I now have 3 noticeable tone changes for my tone control. Maybe my series caps are my volume issue?? I do have a .008 cap that is 630 volts. Maybe tack it in place and see if my volume issue changes??
RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-19-2026
No, this is wrong.
Only series connection of two equal-value parts doubles you voltage rating rating.
In your case, the 0.01uF part will drop way more than your 0.05uF part.
To be exact, imagine them as resistors.
And 0.01 part is 5 times more resistance than 0.05.
So, 5/6 of the voltage (in case of 1200V, for example, it is 1000V) is going to be across the 0.01uF part, which is rated 600V. Whereas across he 0.05uF part you will have jusy 200V.
So, no, this won't work.
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026
Remove the series caps and gator wired in the .008 I have. Did not make a difference. Still has the same volume jump about 2/3 through the control. Had one gator wire come undone and the volume did not change. Left it unhooked, and still have 3 tone settings and the volume still does the same jump. Obviously can’t leave it out but it must just be there for voltage spikes? Did not change the volume or tone levels…
RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026
I measured the volume pot and it all measures correct. Has a smooth resistance change from the swiper to either end. Have narrowed it down to right before the volume spike, the volume goes quiet, then jumps. It is super smooth from the lowest volume to around 2/3 if the range, then the volume goes quiet, then a tiny bit more and boom, the volume goes super load and is distorted. The volume can still go higher and get louder, but the sound is horrible.. maybe I just have a bad volume pot on the upper end. The normal local stations have good volume at the lower 2/3 but weaker stations, when turning the volume up to hear them, it gets to that spot and the sound gets over powered and distorted. Maybe I’ll just leave it instead of racking my brain… for everything else, it is very sensitive, with great sound.