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37-630 code 125 missing all 110 pF caps - Printable Version

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RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026

Does seem odd though that cap #59, a .03 mfd in the Bakelite block is rated at 600V, but then #61, .008 mfd, is rated at 1000V. Wouldn’t a voltage spike damage the 600V cap before it got to the 1000V cap? Shouldn’t the have both been 1000V??

RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026

I’m just going to wire in two .02 630V caps in series. It’s the best I could do with what I have. That will give me a little more protection at .01 1260 V, a little higher than .008, but since it’s just for spikes and doesn’t affect the sound or performance it should work just fine.

RE: 37-630 code 125 missing all 110 pF caps - gary rabbitt - 04-19-2026

Quote:sdradioman  Does seem odd though that cap #59, a .03 mfd in the Bakelite block is rated at 600V, but then #61, .008 mfd, is rated at 1000V. Wouldn’t a voltage spike damage the 600V cap before it got to the 1000V cap? Shouldn’t the have both been 1000V??

It is odd I agree. Essentially the .008/ 1000V cap is shorted to gnd when in the .03uf 600 position.
(My earlier comment about the part #, I was looking at the non code 125 diagram.)

Putting the 2x .02/630 caps in series will work.

RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-19-2026

Wish I could post a video of what it’s doing, but I don’t have a YouTube account. I’m sure if one of you guys heard it you could probably tell what wrong. It’s almost like at 2/3 volume, something gets over driven and extreme volume and distortion kicks in…

RE: 37-630 code 125 missing all 110 pF caps - glyphmon - 04-19-2026

Just putting it out there - Youtube is free, just requires a Google (Gmail) account and to create a channel for it plus a couple initial steps for verification.  The videos don't even have to be public.

Best wishes,
Roy

RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-19-2026

I will explain again, though I already explained the same when I said how the serialized capacitors with the different capacitance would behave.

The 0.03uF would drop 1/5 of the whole volate and the 0.008uF will drop teh rest of the 4/5. So should a 1000V occur across the two, only 200V would drop across the 0.03uF while the resi of the 800V would drop across the 0.008uF.

RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-23-2026

So the issue is definitely in the volume control. I sprayed it with electronic cleaner and the control worked perfect for about five minutes. Then I’m assuming once the cleaner evaporated is when it started acting up again. I’ve got an email out to Mark Oppat to see if he has a control for it but haven’t heard anything back yet.

RE: 37-630 code 125 missing all 110 pF caps - DaleHCook - 04-23-2026

sdradioman' pid-'52 Wrote:So the issue is definitely in the volume control. I sprayed it with electronic cleaner and the control worked perfect for about five minutes. Then I’m assuming once the cleaner evaporated is when it started acting up again.

That is because you used the wrong "electronic cleaner." A contact cleaner is for contacts, not for controls. For controls you need a chemical which cleans and lubricates. I use Caig DeoxIT F5 FaderLube. It is designed to clean and lubricate controls. After the cleaning part evaporates the lubricating part remains and keeps the control quiet. If FaderLube doesn't cure the problem the control is at fault and will have to be replaced.

RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-23-2026

Well, he did not say WHAT cleaner he used, but if it was contact cleaner and not fader lube (D5 (or any other contact cleaner) vs F5), then yes, this will eventually kill that control.

RE: 37-630 code 125 missing all 110 pF caps - sdradioman - 04-23-2026

It was basic contact cleaner…

RE: 37-630 code 125 missing all 110 pF caps - DaleHCook - 04-24-2026

Although I have used only F5 FaderLube for many years, there may be other products that are just as good for cleaning and lubricating controls. Avoid cheap products, though. Years ago Radio Shack sold a TV tuner cleaner and lubricant which was pretty cheap, and pretty poor.

Also avoid products not intended for electronic use, such as WD40. It can be very good on mechanical parts, but it does not belong in or on electronic parts.

I have used Caig products, and before that Cramolin products, for decades at work.

RE: 37-630 code 125 missing all 110 pF caps - RodB - 04-24-2026

Dale, I'll have to disagree with you on dubYa-Dee40. Back when I was in high school I attended an electronics Exposition where companies demonstrated and displayed new products. One demo was for WD40. The fella sprayed it into a light bulb socket, screwed in a light bulb then held it with his bare hand into a small tank of water. WATER DISPLACEMENT 40, Step right up folks and see for yourself! The light stays on.
I'm sure he was standing on a rubber mat.

RE: 37-630 code 125 missing all 110 pF caps - DaleHCook - 04-24-2026

I'm talking about electronics, not electricity. The carbon track on a potentiometer is nothing like a light bulb socket.

RE: 37-630 code 125 missing all 110 pF caps - morzh - 04-24-2026

Rod

Icon_lol a funny example.

A good demo, but what it demoed was the direct purpose for which WD40 (WD is hort for Water Displacement) was created: it displaced water so well that it was not penetrating the screw coupling down to the electrical connection.
Still not a thing for electrical use, though it is in a way a miracle spray and does so many great things that....just amazing.



Sradioman, Dale,

So, it was a contact cleaner, in which case Dale was exactly right: it DOES NOT (^3) (taht is in the third degree) belong INSIDE a potentiometer.
Only contacts. Switches, lugs etc.

Inside - Fader lube F5 or similar products. Never a contact cleaner.

RE: 37-630 code 125 missing all 110 pF caps - DaleHCook - 04-24-2026

It is important to understand the purpose of each chemical, what it should be used for, and what it should not be used for.

I use a variety of chemicals in my work as a chief engineer for radio stations, including:

DeoxIT D5, G5, and F5
91% Isopropanol
Denatured alcohol (use with caution - some denaturing additives may attack plastics or other materials)
Naptha

I sometimes have to use strong chemicals for cleaning, such as removing black smoke stains from the aluminum inner walls of radio transmitter RF cavities. That calls for volatile (and very flammable) chemicals such as acetone or lacquer thinner. Those require gloves, a respirator, and an exhaust fan. The latter is invariably present in a radio transmitter building, for use when the air conditioning fails.