TL431-related (circa) problem - TNT Indiscreto power supply

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Thank you Giaime, for this and other good suggestions.

Since the case is solved, I'll report back to everybody. As Giaime suggested, I raised R1 putting in series a spare 1k I had; this brought R2 from 4.7 to 5.7k, and the source of mosfet M1 (IRF630) dropped from almost 39V to about 36V (just a tiny bit under the max V(KA) of the TL). This mod alone didn't save the damn TL431, though, it just made it pass my first test (about 20 minutes charging, with no load), but when I attached the phono boards and let it run for half a hour, it failed again. So, I also raised R9, from 470 ohm to 1k, and tested it again, with the phono boards attached; it made it through a good couple hours, then I went to bed. Anyway, after 40 minutes or so, the circuit is stabilized, therefore two hours seem good enough to say it's working good.

Now, I have another problem: a strong hum (50 Hz beefy bass noise), which only appears in the neighborhood of max voltage, so I have a few more work to do, which I'll discuss with you guys in an appropriate section of these forums.

Thank you so far ;)

Giacomo
 
TNT InDiscreet

Dunno, in my build the hum was coming from the 9v line so what I have done this morning is ditch the TL431's and implement some zeners in the fashion of Pass Labs preamp power supplies. Problem now completely gone, very very quiet now and sounding great. First time I've used TL431's so may also be my last.........
 
Problem solved

It's maybe a little bit late but, I faced the same humm problem with PSU as the -9V line stabilized. I put a 10 Ohm resistor in series with +27 and -9 lines between the supply and amplifier board and the hummm disappeared completely. The TL431's manual refers to the series resistor...
 
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