phase linear 400

gene french said:
here we go...unit is near pristine...listening to it now...
very happy with the purchase...
looks like the 400c board
clamp caps on power supply...
rectifier on the side too...
pl18 light board with 4 small lamps in the meters...
tell me what you think???
where to start??
Click to expand...
1. Start with the relay board to save speakers, in case the amp fails. Then if an upgrade goes wrong, no speaker loss. Make up a good load box, don't use your speakers doing mods. I just built a nice one... but just start with no load, then connect the 300W 8 Ohms resistors on a piece of wood (easy). Then you can do one channel at a time at 4 ohms, putting them in parallel. Use the series connected 100W lamp to limit the power, in case of a failure...no flames!
2. Then, Replace the Control board, if that's a problem, the outputs getting replaced next anyway.
3. Then do the two input big cap mod, and replace the bridge rectifier for the higher current version.
4. Last but very important, replace the output devices for the new more superior ones.
5. Then do the cosmetics, meter boards etc... Working good, is better than looking good!
6. I would add the DC blocks at the input, and volume control's. Add a power switch to the front. Bring the relay board LED to the front panel...then you always know the offset and balance is correct, and a nice "ON" indicator that all is fine.
Have fun, be patient, and you will have a great amplifier.
 
So, I checked all 7 glass fuses - two on the right channel backplane, two on the left, and all three supply fuses and they are all good. I checked the nuts on the DCP board and those are tight.
 
ABebar said:
So, I checked all 7 glass fuses - two on the right channel backplane, two on the left, and all three supply fuses and they are all good. I checked the nuts on the DCP board and those are tight.
Click to expand...
Did you check the +/- 15 volt rails on the affected channel of the control board?
 
ABebar said:
Well this is interesting. Bias is 0.005v on the affected channel. 0.368v on the good side.
Click to expand...
well you are now onto something...likely an open resistor. With power off and bulk caps drained, check R37R (22 ohms), R41R (22 ohms) and R38R (1 ohm).
 
ABebar said:
I will say, the last time I used it was a party where I went to bed and there were still people there playing the music at extreme volume. It's very possible that something popped after I went upstairs and nobody said anything about it.
I'm stuck at work until 5. I can check all fuses when I get home tonight.
Click to expand...
I bet that after your guests blew your amp, they all quickly went home :-)
 
Gepetto said:
Great, that makes it easy to take measurements on the screw locations. Can you walk down the connector from 12 to 3 and measure the voltage observed with respect to ground?
12
11
10
etc/
Click to expand...
12: -84.1
11: 84.1
10: 0.005
9: 0.202
8: 0.674
7: 84.1
6: 0.0
PNPL: -0.659
5: 0.0
4: -0.009
3: -84.2
 
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