JSX Problem Source

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SoCal Peavey
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JSX Problem Source

Post by SoCal Peavey » Wed Jan 26, 2022 7:08 pm

Hey all, I'm new to this forum here and figured all of your knowledge would help me figure something out.

I've got a JSX, hand-me-down from my brother, who used it for a good while but figured I could use it since he was only using the clean channel on it. I believe it has stock pre-amp tubes in it, but the power amp tubes are Amperex EL34 6CA7, the inside pair from Holland, the outside pair from Britain.

I used it for a good while, just on my desk as a recording head, used it maybe once or twice at a gig, but nothing too hard. Ever since I got it I noticed there was a faint smell from it, however it was there even when it was off, and so I figured it was just the warmth it was generating, as I'd never used a tube amp before. I was correct, it was generating some heat for sure, specifically at this one plug.
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I also noticed that the FC3/FC4 fuse was a ceramic fuse where all the others were regular glass, but it hasn't blown like I thought it had.

I wasn't present when the head died, but from what I was told, it was working fine and then just started to lose volume until it had no output. The main light next to the power switches doesn't light up if it is turned on, the channel indicator lights do work, and it has no volume output. Tubes don't warm up either.

I've got no experience with this, and I am headed to a shop this friday to get it fixed, since I'd rather not blow myself or the head up more than it already is. I just wanted to know what could cause this? I can read some schematics for vehicles but not guitar heads so I was wondering if someone could explain what that plug goes to, how it works, what could cause that, and perhaps how to avoid it in the future. Those 2 yellow wires just run up into the transformer above the IEC port. Thanks for any help and info!

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Enzo
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Re: JSX Problem Source

Post by Enzo » Thu Jan 27, 2022 5:35 pm

That is the high current but low voltage wiring from the transformer for the tube heaters. If the connection at the pins gets resistive - ie electrically dirty - then it can heat. Burnt heater connections are not all that rare. You can hard-wire the yellow wires to the board.

SoCal Peavey
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Re: JSX Problem Source

Post by SoCal Peavey » Thu Jan 27, 2022 5:43 pm

I see. I looked over the forum and saw that someone had a similar issue, however their wires were both just soldered to the board and not in a connection like mine. Is it simply just a matter of cleaning it and soldering it or does that area need to have a new post put into it? I'd assume a new post or pin or something, the other pin near it is about twice as tall, so it seems like something definitely melted and either the post got stuck in the plug or something.

So it's essentially just the fact that it was dirty or a poor connection within the plug? Good to know that it was nothing I had done specifically.

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Enzo
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Re: JSX Problem Source

Post by Enzo » Wed Feb 02, 2022 11:04 pm

You don't have to install new connector parts to hard-wire.

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