Ghost in the machine

Thudstaff · #1 03-04-2011, 10:18 AM

Greetings folks,

I recently purchased an early nineties SVT II in excellent but not mint condition esp for its age. It played fine in the store with no pot/slider/input issues. Once it was perched upon my cabs at the rehearsal space, it initially worked fine. Not soon after she was warmed up, she cuts out with a significant volume reducion and an undesirable crackling sound also at a lower volume than the gain would reflect. I shut her down and return a few days later hoping it would go away. (we do that sometimes

Same problem. Now it's becoming a bit more common. Anyway I take it back to the store and we open the top and fire her up. No problems for the hour she was plugged in.

Here's where I'm going with this. At our rehearsal, as my amp was cutting out, the guitarist's amp fries a tube right upon powerup right about the same time. In fact, he has had amp crashing problems too. Just blew a resistor. Incidentally, we share the room with another band and all of the room's outlets are running on one circuit. There is quite a lot of stuff plugged in throughout the room thought not all on at the same time. Also, the guitar player for the other band blew a resistor on his tube head.

Could this be the source of my problems? The landlord isn't going to rewire the place so are their any safe remedies that don't cost a fortune? Similar stories?

walker rosewood · #2 03-04-2011, 02:02 PM

This sounds pretty obvious. 3 different amps blowing tubes? One circuit? Find a new place to practice, it's the only 'safe remedy.' It's not worth buying new amps for everyone. Electronics can still draw power from the wall even if they are not turned on. If this is a paid rehearsal space then the landlord should rewire, or charge say, $.50 per hour cause that's what it's worth.

The only other thing I can see here is maybe all three of you happen to have mismatched ohms between your head and cab.

fu22ba55 · #3 03-04-2011, 09:18 PM

1) If you haven't done it already, find a good tube amp tech in your area and have him/her bless your SVT II. There are lots of things that could go wrong in there. It's always best to have a qualified tech check out any recent tube amp purchase.

I had a similar issue with my 70's SVT... I had to have the bias circuit rebuit, and it was well worth it.

2) I've been suspicious of "accursed" AC power in rehearsal spaces before... but it usually can be attributed to a bunch of amps that had been sitting around suddenly being used three times a week. If you're really paranoid about it, you could borrow someone's power conditioner and see if AC ever drops way below 110, but It's more likely that you guys are working the bugs out of amps that need some general maintenance.

Most guitar players need to have their cute 'lil guitar amps serviced after I show up with my SVT for a couple of weeks. The SVT makes most pissant guitar amps stand and deliver.

Thudstaff · #4 03-05-2011, 02:26 AM

Sorry for the late reply. We did some voltage testing on the outlets and the whole room is pretty screwed up voltage-wise. The space is part of an old brick warehouse that was converted and I'll bet the wiring could have been half assed. I don't think it's the amp at this point because my signal was affecting the guitarist's signal causing him some crackling. Now I wonder if the room is even grounded properly. What a mess. If we don't get the landlord to fix this, I guess we call the city but that shuts everyone down until it's fixed. We'll see. Thanks folks for the help. When that SVT II is on all cylinders, watch out!

Oh, there happens to be another older SVT black face from the early eighties (Japan?) and it seems unfazed by the voltage fluctuations, at least audibly. What a beast. Cheers!