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i just got a JTM30


ilovemystrat

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I used to have a 1x12 JTM30, back when they first came out. I remember it was $400, new. I wound up wrecking, and the amps knobs got sheared off...the entire pot shafts, basically. I remember my dad and I tried to get new pots and fix it, but it still didn't really work quite right. That was in 1997.

In around 2000, maybe 2001, I traded it straight up to a guy for my '81 Yamaha Maxim 550, which I used to ride more than I have lately (though I intend to get it out more this spring). The guy I traded the JTM30 to got it fixed up, and was gigging with it not long after that.

I had a JCM800 6-knob combo at the time, and the JTM30 was my "small amp" and backup, basically. I remember it being a good sounding little amp, though.:thu:

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i got a little random volume drop problem, anyone else had that problem?

 

 

My first thought is how old are the power tubes? Are you sure it's the amp? Have you tried different cables/guitars? If so you might wanna start with the preamp tubes, swapping them out one at a time to see if the problem gets resolved, otherwise try replacing power tubes. Even if they are new power tubes, they could potentially be faulty.

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My first thought is how old are the power tubes? Are you sure it's the amp? Have you tried different cables/guitars? If so you might wanna start with the preamp tubes, swapping them out one at a time to see if the problem gets resolved, otherwise try replacing power tubes. Even if they are new power tubes, they could potentially be faulty.

 

 

yea, it has seemed to stop? i switched the standby switch on/off and it got better instantly.

 

the clean channel doesnt seem to do it, only the dirty, i read this is a common problem but i think its easily fixable especially here in tokyo.

 

any other suggestions? and how do i remove the tubes?

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I picked up a 2x10 version a while back for $250. The tolex is messed up but it sounds great. There are a bunch of threads on here where their reliability is said to be not so great, so I was kinda surprised when mine worked so well, especially considering that it looks like it's been through the wringer! Did you get the 1x12 or the 2x10?

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The 2x10 is SO incredibly lightweight! It feels like a toy, which I'd bet is mostly because its transformers are much less substantial than the "big boys." The sound of the amp doesn't really seem to suffer though. I was pretty impressed with it.

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  • 3 months later...
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I have one-. When I got it there had been some problems (melted solder joints from overheating). We put thermocouples on it in the lab at work and pulled the tube shield off. The internal temp dropped dramatically. I haven't had any problems with it since (knock on wood). I am replacing the speakers and have some NOS RCA 6L6's in it because the plate voltage is way too high and I wouldn't trust any new tubes at where it's biased at (the stock tubes didn't sound all that great anyhow). It is also a PITA to work on. BUt when it's cranked up it really sounds good. As good as some of my vintage stuff. And it's easy to transport around.
I can see why people have a love/hate realationship with these. I hadn't used mine for a while but played out with it last week and it sounded so good I may build a pine cab. for it and add an easy to reach bias control. A new power transformer to drop the plate supply at least 10 or 20 V wouldn't hurt either. At the price these are going for they are a bargain for those who have tube electronics experience and are willing to do the work.

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