I Need Your Help To Solve A Problem

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[@DERB_Seymour_Indiana]

Hey Jack, as Bob will surely tell you, ground planes can wreak havoc on circuit designs. Normally if the device is hooked up electrically the same, the circuit should work. But adding or changing the ground plane in an RF sensitive device can make a big difference. In this case, when the device is added to the circuit and not powered on, the operation should be the same as long as it is hooked up correctly. To that end I would say something isn't right with the new cap. If you can get a range of values just measuring it by itself, but not when you have it hooked into the circuit, I think you can see where I'm headed. :) I would concentrate on mounting the device in a way that produces your normal range of values and if you get that far, then you can see how it affects the circuit in actual operation. To do that, completely isolate the mounting from the chassis as the old one did and then add wires to connect the device the same as the old one. Hope that helps. 👍

[@VintageElectronicsGeek]

Bob sent me a email and I just replied....thats one step I didnt think of doing, Ill put the cap outside the case and run short leads...the cap does measure just fine on its on...let me try with flying leads and see what happens...thanks for the idea and help! ~Jack, VEG

[@DERB_Seymour_Indiana]

@@VintageElectronicsGeek Good deal Jack. I was hoping Bob would chime in on this as well. :)

[@TheRadiogeek]

If you can get a measurement on the new variable capacitor then hook it up outside of the case with some clip leads an see if it works. You can hook it up different was quickly. As for the old variable cap try some JB weld on the shaft? This is my cheap guess. 😀

[@VintageElectronicsGeek]

Great idea, didnt think of that step, der! :) The cap does function standalone. Thanks for the help! ~Jack, VEG

[@Steve-xl2mn]

@@VintageElectronicsGeek For reconnecting the shaft bits, a dowel pin approach: center drill both loose shaft sections to accept a roll pin, and fill gaps with J-B Weld (allowed to thicken, to reduce out-flow). Check alignment carefully and brace to cure, with capacitor section "up", in case the epoxy does flow down shaft. Duncan Amps has a nifty free tube data resource, compact & self-contained. Seems like I can't list links, but Duncan's Amp Pages should bring it up.

[@westelaudio943]

Wow Jack! I totally missed this video. Did you end up getting the banana slicer to work? I have no clue anyways. I suppose the cap mounting bolt should be isolated from the chassis for shielding. I'm not too good with this RF stuff. Normally I'd expect the cap to work just like a fixed value one. Maybe it's inductance is too high? But this thing doesn't look like the frequency would be high enough for that.

[@VintageElectronicsGeek]

No worries, we all have busy lives....I did get it working for the most part...for now any way....a future video will come out when I have time....its recorded, just need time for editing. ~Jack, VEG

[@jimkodysz5404]

Hi Jack, While T don't have an answer to your dilemma, I do have several ceramic caps here. I will gladly send them out to you so that you can try substitutions, etc. If you find one that works, just send me back the unused ones. Send me a PM

[@VintageElectronicsGeek]

Hey Jim, that is very kind of you! A few suggestions came my way, let me try them first and we'll go from there! Your awesome, thank you! :) ~Jack, VEG

[@VintageElectronicsGeek]

Jim - How do I contact you, you dont have an email/contact setup on your YT channel. ~Jack, VEG

[@LarryDeSilva64]

Jack I have a 158-4-2 air cap ceramic that looks similar to what you pulled out but I can't tell if mine is the correct one for that application. Did the air ceramic cap you pulled out have a stenciled number on the top? Let me know. If its 158 pf that's what mine is measuring.

[@VintageElectronicsGeek]

Larry - It reads: Hammarlund A-?-20-I , the second character is either missing or faint and illegible, the “I” might be a “1” or a “L” or a "1", it’s a straight line. ~Jack, VEG

[@LarryDeSilva64]

@@VintageElectronicsGeek well Hopefully you got the part I sent on Monday.

[@VintageElectronicsGeek]

@@LarryDeSilva64 Got it Larry, thanks to you and your friend! :) I have a amp on my bench now, when I'm done with it, Ill put the other one back inline. Thanks again! ~Jack, VEG

[@umajunkcollector]

looks like you got the help, cheers!