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NOCD

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RICH

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Hey, I brought that ampeg ( ampschmeg) V-4 to the amp dude. I don't know what was wrong with it, but it only cost $52 to fix. I have a feeling that it was real stupid simple. I'll let you know when I find out. Hey BTW, I left a question in the negative feedback thread.
 
NewOldCokeDave

NewOldCokeDave

Active member
Joined
Jul 16, 2001
Messages
4,945
I'm dying to know what the problem was!! Let me guess, a screen resistor?? This has been driving me nuts ever since you brought it up...

I left an explanation as best I could on that ther thread.. Hope it helps.. Now I have your headache!! ;)

-NOCD
 
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RICH

Guest
Well, my bass player picked up the V4. The dude who actually worked on it wasn't there, but on the bill it said something about changing a bias resistor to 100K for more B- for 6550 tubes, AND could NOT confirm a glowing tube. Well it isn't glowing anymore, so he probably fixed it before he even fired it up. He gave it a scope test and a guitar test. I don't know, when I measured the bias it was like -60, which I thought would be cold for 6550's, which is why I gave up on it, because I know NOTHING about ampeg. Who knows?
 
NewOldCokeDave

NewOldCokeDave

Active member
Joined
Jul 16, 2001
Messages
4,945
That's really weird as when I looked up 6550s, -60 wasn't unreasonable, depending of course whatever the plate voltage is.
You'd think with a bias problem, there would be more than one tube affected. I think the Ampeg schem called for -51 or something around that.

I tell ya, tube amps are among the most fickle beasts out there!

-NOCD
 
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Ed Rafalko

Les Paul Forum Member
Joined
Jul 15, 2001
Messages
6,287
TRy debugging a solid state Marshall Lead 12 sometime. I have two of them, and on both, they squeal like pigs when I pin the gain.
Both also had to have their pots cleaned out before I coudl get anything decent out of them.
On one, the delinaition of bad sound is VEYR clear- it's instant- a lous hiss comes out of hte amp, like I'd just bumped the volume 100 percent, and the disotrtion sounds like shit. But if I put the gain right at th epoint just before the hiss begins, it sounds great.
The other amp works better but has a very raw high end.
Do any of these symptoms sound familiar to you?
 
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