Power transistor help

wattsabundant said:
You have to be careful with test gear and ground connections on the C-500. The right channel is inverted and the white binding post is at ground potential.
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Yer right Don. Carver amps (The Magnetic Field Power Amp variety) that have the Triac's in the circuit will also ruin your day if you are not careful when using the ol O'scope. Not following the "Danger Warnings" in the Service Manuals, you'll blow some retinas out..... I think it was from using a grounded Scope Probe on the triac. I stayed well away from them.
 
Good morning, everyone.

Again, I need someone's help. I've started my second amp. Another Phase linear 400. I'm on step #18 from Joes backplate bring up recommendation. There he has us check for no voltage at the output terminals. Right channel is reading .000, but my left channel reads .139. I don't know where to go from here. I'm sure one board is good. I've compared and measured both boards side by side and cannot find a difference between them. Can someone steer me in the right direction? What should I be looking at or for? Note: All that's installed is the bottom row of transistors.
 
WOPL Sniffer said:
Yer right Don. Carver amps (The Magnetic Field Power Amp variety) that have the Triac's in the circuit will also ruin your day if you are not careful when using the ol O'scope. Not following the "Danger Warnings" in the Service Manuals, you'll blow some retinas out..... I think it was from using a grounded Scope Probe on the triac. I stayed well away from them.
Click to expand...

Yea, I learned the hard way with scopes that are grounded through the AC input plug. We used a 2.2 ohm 1/4W resistor on the ground lead. 2.2 ohm as we had a pile of them. That doesn't fix the problem. It just does less damage to the probe.
 
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