Need help verifying if the PL14_20 Control board kit will work in my 400S2

So I have used the diode function of a Fluke 87 to test them all and what I found was the top two (Motorollas) on the right channel were fried. On the left channel they all seemed fine-ish. 3 of the Motorollas tested at .41-2 V when I did base to collector. All others were between .45 and .5 V. So I guess that explains why the right channel fuse blew. Any suggestions on the left channel blowing the fuse?

Thank you again everyone!
 
You have 2 rail fuses correct? One for the negative, and one for the positive...did you do all 6 tests on each one?
 
Yes 2 rail fuses. And yes I did all 6 tests. So the fuses aren't for each channel I'm guessing right? Implying that the blown OTs were one from each rail?
 
dmccan13 said:
Yes 2 rail fuses. And yes I did all 6 tests. So the fuses aren't for each channel I'm guessing right? Implying that the blown OTs were one from each rail?
Click to expand...
in PL400's the rail fuses are shared between both channels. The PL700's had fuses for each channel.
 
So, when I replace those I need to "recalibrate" using the Oscope, signal generator, etc
 
dmccan13 said:
So, when I replace those I need to "recalibrate" using the Oscope, signal generator, etc
Click to expand...

Hi Drew
No. Once you get healthy outputs installed, you will only need a DMM to bring it back, check the offset and set the bias. When you bring back up, do it on a DBT so you can tell if things are OK or not. Turn your bias pots to minimum, full CCW upon DBT bring up.

What do you have in the back wall right now, have you posted pics of what is in there?
 
Gepetto said:
Hi Drew
No. Once you get healthy outputs installed, you will only need a DMM to bring it back, check the offset and set the bias. When you bring back up, do it on a DBT so you can tell if things are OK or not. Turn your bias pots to minimum, full CCW upon DBT bring up.

What do you have in the back wall right now, have you posted pics of what is in there?
Click to expand...


Ok, I went down the rabbit hole last night and got in over my head in some of the posts here. That's where I got the Oscope idea. So do I hunt down 2 NOS TP9054s? Or am I good with the MJ (?) replacements? I haven't posted pics, but I'll do it now...
 
TP9054s are just MJ15024s that have been private labeled for Phase Linear.

MJ21196G devices are superior to the MJ15024
 
The outside Drew, not the inside...
with transistor covers snapped off.
 
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