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I'm working on a Gallien Krueger 200MB with a host of problems. The biggest being that I'm only getting +2.0vdc and -2.0vdc at the rectifier. Currently (no pun intended) I have the rectifier disconnected from the board with jumpers running from the power switch to the AC side, where I'm getting 59vac. The rectifier tests good and I get the same reading from any replacement I try. These are kind of a strange design where the transformer gets power before the switch. Is there something I'm missing that could be pulling the voltage down?
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So just think of it like an effect pedal with a wall wart, as long as the amp is plugged in the transformer is powered on.Originally posted by stereomonostereo View Post
The 60 volts ac is the output of the transformer it is center tapped, so there should be 30 volts ac at each of the rectifier inputs, referenced to ground.
If the circuit was pulling down the output from the rectifier to 2 volts, the fuse would blow and things would burn up. Are you using a limiter for these tests? -
My AC voltages seem right. And reading from the center tap ground of the secondary, my rectifier voltages are correct. I'm going to see if there's a problem with the groundComment
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How were you reading 59 volts before?Originally posted by stereomonostereo View Post
The transformer plugs into the board doesn't it? Pull the plug and read the ac voltages directly at the plug and if need be, at the transformer itself.Comment
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The ground I was reading from was bad and giving me incorrect voltages. Now reading off the center tap my rectifier voltages are spot on. My problem now is that I'm not getting my -15 volt feed. I'm reading -42.2 volts on R221, but it's dropping to -2.1 volts on it's other side. Something in the chain is shorted and drawing it down.Comment
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I don't see where R221 is.Originally posted by stereomonostereo View Post
Are any of the ICs getting hot? The other component that often fails are the small decoupling caps.Comment
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