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Phase Linear 400

It really looks like either Q7 is short, or the regulated voltages in the front end are way too high. Those little regulators are not that hard to kill with heat. The regulators test like a diode jct.
 
The feedback loop should be established and the front end should be taking control at 60 volts, so you should see DC volts diosappearing before you top 70 volts so let's leave the DBT in for now.
 
With amp powered down, caps dischargedand all fuses out----
Neg probe on base--Pos probe on Emitter--.640 volts DC
"" "" " " Pos probe on Copllector---.620 volts DC


Pos on base------Neg on Emitter-----1.600 volts DC
Neg on Collector---Infinity

Pos on collector-neg on emitter----.499 volts DC
Neg on collector--positive on emitter----Infinity.
 
That is a two sided board, it has traces on both sides. All components need to be soldered on both sides except those caps that sit flat. Check all those again and look for solder bridges or cold joints.
 
That could be some of your problem. There are traces that go from the top to bopttom through the Thru-holes, so a good solder joint that goes all the way through is essential, so is flipping it over and soldering the back side.
 
Thats not mention in the instructions . "tack solder one lead from the top side and flip over solder both leads from bottom." No problem though if thats what it takes
 
Most of components were ok the solder came through to the top side . But I'm still getting 40v at R34r & R35r
Tomorrow I will redo Q6 on the right .I'm getting those high reading there too.
Thanks for hanging in . I really appreciate it.
 
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