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High voltage arcing in amp?

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Crusher said:
That is true KW, but seems odd that on low it was fine and hi setting it is not. But then this is RF and all sorts of strange things can happen.
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Yes but remember that the high setting may increase the plate voltage but it also increases the RF output. If that loading cap was in any way compromised by a defective or bent plate it may only arc on high.

What about wire from loading cap to relay. Is this a good solid connection. I have seen a transmitter with a bad connection at cap and the rf is trying to find a path. Just a thought.
Click to expand...

Any loose connection can easily arc and that would in turn cause a huge change in the reactance voltages which could very well lead to a breakdown of the loading cap. Plate voltage is one thing, RF voltage is another albeit much lower than typical plate voltages however when it comes to reactance voltages all bets are off. It is not unusual to have several thousands of volts develop in an antenna tuner or amplifier when things are not right. The big reason I say the loading cap has the proper plate spacing is that it was built that way and obviously worked fine before.
 
I am not doubting you in anyway. Just exploring ideas. Also as you mentioned, it worked for what it was designed for. But as to drive level or what he is driving it with. Maybe he mentioned that. Not sure. Just trying to explore all possibilities.
 
Crusher said:
I am not doubting you in anyway. Just exploring ideas. Also as you mentioned, it worked for what it was designed for. But as to drive level or what he is driving it with. Maybe he mentioned that. Not sure. Just trying to explore all possibilities.
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That's how issues get solved. Lots of talk about everything that comes to mind regardless of how likely or unlikely something is.(y)
 
You never had a big enuff linyeeare

Once you convince them it's THEIR fault because it's still getting bleedover while UNPLUGGED, they believe you :)

Or they believe that it's posessed. Either way, usually the device offending YOUR GOD GIVEN RIGHT TO OPERATE is gone.

:)

--Toll_Free
 
Yep may just have to get a bigger one. I like the saying, if you need more than 1 tube, get a bigger tube!.

I was driving it with a stock galaxy dx 959, with a carrier of a little less than 3 watts swinging up to about 13, nothing this box should have a problem with at all. Another thing, this box is actually a 20 meter cw transmitter, no the 15 meter one. I never seen one like this before but it says 20 meter CW transmitter on the front. My coil is also 6 turns for the tank, and 18 for the other one. I fired it up for the first time in a few days last night to watch where the arc was coming from again, and now it seems like it is only throwing a weak carrier out... :bdh: All other knobs can be tuned, but now the plate load knob is now functionless. I let it warm up for about 10 minutes and just did a very quick key like all the other times now its barely putting out 50 watts. I think someone may be getting a good deal on some new 6lq6s here pretty soon possibly.
 
I think its is the dc blocking cap on the tune side failing at high power. Id replace that and the air variable on the load side and key up. Really how much can those parts be? $40-$70?
Also please don't kill yourself.
 
Oh now I see the dc blocking cap,thats not there?! :mad: Well there is/was no dc blocking cap in this box... Also I made a new tank coil with 1 1/16'' form, 4 turn copper wire and installed it just like you did with the old phantoms so it has the same circuit now besides that dc cap... Im suprised it didnt have a blocking capacitor on there in the first place, I dont even think they did from the factory? But I will definitely add one if I can get the thing to put out more than 50 watts. Tubes are fine, plate tune has lost function. Worked one second I checked it, now its extremely weak, not sure what I did but everything still looks fine, no burnt resistors, chokes or caps.. This all happened after a couple second keydown to figure out why it was arcing over the plates. :oops:
 
linearone said:
You are changing tank coils and fiddling around with things that are not the problem at the moment. Shotgunning parts and changing things will only get you lost. stay focused on the problem at hand.
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The OP started out with a working amplifier that was arcing in the load gang and now, he is changing parts out that are not problematic. The amp had to have had the DC Blocking Cap in it to be working in the first place and, there there was nothing wrong with the Tank coil.

*I* believe that the original problem was caused by a mistuned amplifier or, a problem in his antenna circuit; in hindsight, did anyone advise the OP to tune the amplifier into a non-radiating dummy load?

It takes a lot time to be qualified to repair an amplifier.*




* I am trying to be nice!

.
 
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Well... my "shotgunned" coil produced an extra 50 watts so how about that??? Nobody was right as far as output.. It was called a defective mica insulator on the loading cap... Check continuity, it was shorted by the little metal strip.. Removed 2 screws and bent the tabs back... Back to normal.. Told ya the coil was made by a two year old that just learned to solder... So my coil works, sparking persists but I dont care it works. :oops:
 
3022 said:
Well... my "shotgunned" coil produced an extra 50 watts so how about that??? Nobody was right as far as output..<snip> .....<snip> So my coil works, sparking persists but I dont care it works. :oops:
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<church-lady voice>"Well, isn't that special". </church-lady voice>

Congradulations on your repair, I am glad that your "scientific approach" to trouble shooting solved(?) your initial problem of "High Voltage Arcing" in the Load tuner or, did it?

Good luck with your amp and, *we* look forward to hearing more from you, as, you are now qualified to help those who know less than you.

.
 
  • Like
Reactions: Naysayer
3022 said:
Well... my "shotgunned" coil produced an extra 50 watts so how about that??? Nobody was right as far as output.. It was called a defective mica insulator on the loading cap... Check continuity, it was shorted by the little metal strip.. Removed 2 screws and bent the tabs back... Back to normal.. Told ya the coil was made by a two year old that just learned to solder... So my coil works, sparking persists but I dont care it works. :oops:
Click to expand...

So your coil works, but your amplifier still doesn't.

Even though you reported you 'found' the problem of the mica insulator, you state it STILL arc's.

Either English or repair isn't your good point. We are all waiting to see which it is.

--Toll_Free
 
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