I could use some help with troubleshooting of the front stage. Both channels are behaving the same way:
1) all components mounted, 34v power switched off, 39v switched on and stable, one diode bypassed.
2) all leds lit happily
3) voltage drop across diode string is 1,5v, too low to turn on power stage. Voltage drop across trim pot 0,7v.
4) If I turn on power stage voltage, diode string drops even less voltage, around 1,2v, and none of the njls turn on at all.
I have no idea. All transistors around diode string were off and I couldn’t figure out why. There were no mistakes to be found. While I was poking around, suddenly everything turned on and string was biased. It seems like a bad solder joint somewhere which I poked at some point.
My output transistors seem to be badly matched, as I have variations from 16 to 22 mV at output resistors. Need to repeat that exercise with different approach.
My output transistors seem to be badly matched, as I have variations from 16 to 22 mV at output resistors. Need to repeat that exercise with different approach.
I have made a compilation of all useful tips and comments from this thread in one doc, to make the build of this wonderful app easier. If you feel anything else should be added, please let me know.
Fc100 - Google Docs
Fc100 - Google Docs