Thanks for the confirmation, Allison.
? ?When I removed (almost) all of the parts from the board for the pre-driver, I checked R961.? Since it measured the desired 2.2 ¦¸ I left it.? Everything else was replaced.? With the amp rebuilt, I had 13.5V in on that resistor and 10.2 on the other side.? I just swapped that 2.2 ¦¸ for a fresh resistor and the entire power chain is alive again.? I feel for the analog meter in the WM-2, but it was good to see it pegged again!
? I replaced every single part in the first three amps.???I wish I knew what happened.? I've never seen passives fail like that.
? ? Thanks for the hand-holding, ma'am.? Mission complete.
? ? Andy
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On Sun, Nov 25, 2018 at 11:26 AM, ajparent1/KB1GMX wrote:
AndyH,
Allison - is the 5V at the collectors reasonable?? If so, is it time to replace R92 and R95 with pots and adjust until it works?
No.? NEarly all of the collectors from Q90 on are connected to the 12V bus (that is at 12V???) so unless the small
value resistors re cooked that is just plain wrong.? Check R84 (10 ohms), R89 (2.2ohms), r961 (2.2 ohms).
One end of each of those should 12v or higher and the other may be a few tenths less.
Allison
