Went through all three boards (one channel) all resistors are spot on.
Reflowed all the solder joints (they all looked solid before)
Pulled jfets , Tested on one of those cheapee transistor component testers . Check out as N and P channel Jfets (i know that's not the end all tester but it would point out if they were shot maybe). Interestingly one checked good in circuit the other not But out of circuit both tested good.
Rails at 33.6v +/- (i'm guessing if i were actually drawing current it'd be slightly less.
For sake of ruling out jfets i ordered 2 new matched pairs.
Is there anything else i can check (test ?) in the meantime?
Reflowed all the solder joints (they all looked solid before)
Pulled jfets , Tested on one of those cheapee transistor component testers . Check out as N and P channel Jfets (i know that's not the end all tester but it would point out if they were shot maybe). Interestingly one checked good in circuit the other not But out of circuit both tested good.
Rails at 33.6v +/- (i'm guessing if i were actually drawing current it'd be slightly less.
For sake of ruling out jfets i ordered 2 new matched pairs.
Is there anything else i can check (test ?) in the meantime?
Test the MOSFETs to verify they are not shorted to the heat sink from the mounting. Best to test before you have bias, otherwise the MOSFETs have a way of being obvious when shorted.
Other than the wiring, your left with the 1 ohm resistors and the diodes.
I think your decision with the JFETs was very wise, mark the old one you have a question about with tape.
Other than the wiring, your left with the 1 ohm resistors and the diodes.
I think your decision with the JFETs was very wise, mark the old one you have a question about with tape.
I like the thermistors with the eyelet connections vs. the "bend to make contact" type. Easier to use for me, and by definition, you don't have to worry about that potential failure mode.
Good discussion earlier in the thread with part numbers.
Sheesh - you guys move fast...
Went to grab a coffee before posting. Above is in reference to post #1166.
Good discussion earlier in the thread with part numbers.
Sheesh - you guys move fast...
Went to grab a coffee before posting. Above is in reference to post #1166.That was quick.
One thing I would have suggested trying is measuring voltages to ensure
you have good continuity: Literally have one probe on ground and use
the other to measure the voltage at all the connection points
from R5/pos rail down to R6/negative rail.
Since you already have the jfets out, perhaps you can try measuring their Idss?
You can see post #6674 here on measuring the p channel 2sj74/lsj74:
https://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide-668.html#post6677716
You can use a 100R resistor.
For the n channel jfet (2sk170 or lsk170) just switch +/- on the battery.
If you have BL grade (Toshiba) or B grade (Linear Systems) jfets you should see between 0.6 and 1.2V
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This link might help you Pheonix. And as member Elmwood625 said, it is important to check every pin of every MOSFET and make sure none of the pins have continuity with ground (the mounting screw/fenderwasher and/or empty non anodized hole on the heatsink or heatsink bracket mount screw, etc...).
Best,
Anand.
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That meens you only use 1 thermistor for N-ch side, and 1 thermistor for P-ch side. No matter how many P-ch and N-ch boards you got for each channel.
A F5T v3 uses 2 N-ch and 2 P-ch boards for each amp channel. but you only use 1 thermistor for N-ch side and 1 thermistor for P-ch side.
Think i have one channel licked. after pulling whole side, pulling mosfets. Testing all. While
I clearly don't completely understand how this works. there just isn't much to it .
so i test power to outside hole of each output board and N side is giving me + reading.
I trace and test all along and everything appears good . So its a common (-) pad on front end . in getting -33 out getting +. Not possible , scratching my head.. So i reflow power lead from supply and (-) lead going to N out board and bingo. Just brought to 100mv on each side with about zero offset. As much as i can get to tonight.
Appreciate guidance so far. I think the other channel has a different issue but tommorow is another day.
I clearly don't completely understand how this works. there just isn't much to it .
so i test power to outside hole of each output board and N side is giving me + reading.
I trace and test all along and everything appears good . So its a common (-) pad on front end . in getting -33 out getting +. Not possible , scratching my head.. So i reflow power lead from supply and (-) lead going to N out board and bingo. Just brought to 100mv on each side with about zero offset. As much as i can get to tonight.
Appreciate guidance so far. I think the other channel has a different issue but tommorow is another day.