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Re: Ampeg SVT 3 Pro output has DC

11/6/2005 11:57 PM
Erik Miller	Re: Ampeg SVT 3 Pro output has DC "Hook up your lightbulb limiter to the thing so it doesn't do sudden death before you can probe it. And use a dummy resistor load unless you have a rotating magazine of test speakers. " Yeah, well, what I did was bring the thing up on my variac, carefully monitoring the AC current draw. This has worked wonderfully for every other solid state amplifier in the past. However, this piece of equipment has a dandy soft start feature that provides a time delay or something before the power amp actually comes on. So it came up just fine on the variac, sat there, and then blammo. With the lightbulb limiter and connected to the dummy load, I get the cycle up/cycle down thing. The lightbulb glows very brightly for a second, then click, it's back down. I'll try your suggestions regarding bias; I've actually pulled the driver transistor out of the board and checked it on a meter, and it's supposedly good. Working on anything with the letters "SVT" in its name is a pain in the ass, no matter what the technology.

11/6/2005 11:57 PM

Erik Miller

Re: Ampeg SVT 3 Pro output has DC

"Hook up your lightbulb limiter to the thing so it doesn't do sudden death before you can probe it.

And use a dummy resistor load unless you have a rotating magazine of test speakers. 8-)

"

Yeah, well, what I did was bring the thing up on my variac, carefully monitoring the AC current draw. This has worked wonderfully for every other solid state amplifier in the past.

However, this piece of equipment has a dandy soft start feature that provides a time delay or something before the power amp actually comes on. So it came up just fine on the variac, sat there, and then blammo.

With the lightbulb limiter and connected to the dummy load, I get the cycle up/cycle down thing. The lightbulb glows very brightly for a second, then click, it's back down.

I'll try your suggestions regarding bias; I've actually pulled the driver transistor out of the board and checked it on a meter, and it's supposedly good.

Working on anything with the letters "SVT" in its name is a pain in the ass, no matter what the technology.

Replies:

R.G. I used to use a variac too, but I g... -- 11/7/2005 9:57 AM