Jet City Weirdness

[marnold***]

OK, here's a puzzler. I plugged in my guitar and cranked up my Jet City. No sound. Oops. I check the obvious things (are my cords plugged in, volume up, not in standby, etc.). Nothing. I plug directly into the amp. Still nothing. Switch cords. Nothing. Power indicator is lit and the tubes are glowing. I crank the volume and gain. Then I can hear something, barely. It _sounds_ OK, just phenomenally quiet. Those settings should make me immediately deaf, but I can barely hear anything. I turned off the amph and called for my son (who thankfully brought my old '51 back from school) to bring his guitar down here. I turn the amph back on and plug his guitar in and am immediately greeted with loads of 60 cycle hum from the neck single coil. Everything is working fine. Hmm. Maybe my jack is going on my DK2M? So I plug that back in and everything works fine.

Any ideas what might cause this? I've never experienced anything like this with this amph. Is this a sign that the power tubes are on their way out? These are the stock Chinese tubes. I got the amph almost two years ago. If it is (heaven forbid) croaking, I did buy a two-year warranty on it at GC which ends February 15.

[sunvalleylaw]

Sorry I can't help on the amp. But I thought you were talking about this kind of Jet City weirdness.

[Spudman***]

Try turning the amph on and plugging in random cords. Touch the end of each cable with your fingers to see if you get a ground hum that way. This will eliminate the guitar being a factor.

Also, when they are cool, make sure all the tubes are firmly seated in their sockets. And finally, make sure the speaker leads are tight on the speaker.

Good luck and happy new year.

[marnold***]

Try turning the amph on and plugging in random cords. Touch the end of each cable with your fingers to see if you get a ground hum that way. This will eliminate the guitar being a factor.

Also, when they are cool, make sure all the tubes are firmly seated in their sockets. And finally, make sure the speaker leads are tight on the speaker.

Good luck and happy new year.

Thanks. For the first, that's why I had my son bring down his guitar. I guess it is still possible that I have a short in my guitar's wiring. I'll see if it happens again. I did try several different cords. There wasn't even any noise when I hit the cord against the jack or inserted/removed it, so that would seem to speak against the guitar being the culprit. I also checked the speaker leads (and the power cord). I'll check the tubes at some point here. I wouldn't _think_ any of them have become unseated since it has almost never left this exact position, but nothing's impossible.

[marnold***]

Sorry I can't help on the amp. But I thought you were talking about this kind of Jet City weirdness.

Actually I was ahead of you. After I posted I tried to change the title. I know that Seattle has its own unique brand of weirdness

[marnold***]

Well, I've been away for several months now--haven't felt much like doing anything with guitar. Recently I decided to pick it up again. The problem is that my amph is doing the same thing again only this time it won't go back. I tried reseating all of the tubes. I swapped out the preamp tubes, then the power amp ones. I tried multiple guitar cords. I checked the connections in the cab. The only thing I haven't done yet is tried a different speaker cable, which I will this weekend. Any ideas, Tung? DVM? Bueller?

[Robert****]

Have you tried with another guitar? Sounds like a strange thing.

My JC20H has not had one issue yet.

[marnold***]

Yeah, it does the same thing with my son's Squier 51. Unfortunately the guy who did work on it before will be AWOL for a while. This happened the first time before he ever worked on it, so I know it's nothing he did.

[marnold***]

Just tried the amph with a friend's 4x12 and his speaker cable. Same problem. Guess I'm amphless for a while.

[marnold***]

I finally got it to a tech today. It turns out that a lug on the master volume was grounding ever so slightly on the chassis. Basically, it was like the master volume was almost completely off even when it was cranked. A simple fix but it took a bit to find. It cost me about $70, but it's working again!

[Robert****]

Congrats!

Now rawk out!!!

[NWBasser]

Niice.

I love it when it's something simple and cheap.