Before replacing D4,D5 there is 1.94V on LED terminals. Unfortunately I have don't have spare E-152. I have to order it.
OK, no need to replace D6 as voltage at the D7 LED confirms that right current is passing through (controlled by D6 Current Regulator Diode). Replace D4 & D5 and let’s see.
After replacing D4,D5 nothing changed. 0.394V can be measured on D4, and D5. 0.8V sum on D4,D5. Green LED lights.
Next, some silly questions.
Are Q6 & Q7 for sure TTA004?
If they are, one of those two could measure BE junction as low resistance at any polarity, which means failure.
Check that next.
Are Q6 & Q7 for sure TTA004?
If they are, one of those two could measure BE junction as low resistance at any polarity, which means failure.
Check that next.
I checked Q6 and Q7. They are TTA004. Only Q8 is TTC04. The error is silly, not the question. 🙂
If that was multi-meter’s diode measurement mode measured at the powered down circuit, Q6 seems OK. If that was voltage measured over BE at the powered up circuit, it is not solid confirmation that BJT is OK.
But, Q7 is as well in parallel with D5 & D6 diodes and should be measured as well.
As there is nominal current through D6 & D7, but there isn't enough voltage over D4&D5, one BE junction (Q6 or Q7 or both) may be conducting all the time and limiting voltage over diodes.
But, Q7 is as well in parallel with D5 & D6 diodes and should be measured as well.
As there is nominal current through D6 & D7, but there isn't enough voltage over D4&D5, one BE junction (Q6 or Q7 or both) may be conducting all the time and limiting voltage over diodes.
In this case, voltages won’t tell us if Q6 or Q7 are damaged. Use multi-meter resistance mode or specific diode measurement mode if available and check BE junctions on the powered down circuit.
Other solution is to replace both Q6 & Q7.
Other solution is to replace both Q6 & Q7.
I replaced Q7. Nothing changed. With multimeter I measured BE BC junctions on desoldered Q7 and it was ok. I have parts and pcb for a second one, so I build a new one. Than I can compare.
Exactly 🙂 Use flux if you have, if not add more solder, it needs to flow more according to your posted images.
Why didn’t you check or replace Q6 as well? Q7 and Q6 both have BE junction in parallel with D4 & D5 and if any is damaged, that can cause problem exactly as you have.
I got my first pair of these up and running today and installed them in a couple of different amps to check them out. The improvement is not subtle. I will be building more. Thanks for these tombo56. A really nice job!
@Vunce: consider the impact on output impedance. Even with #10 AWG wire, a 75 cm umbilical will add about 5 milliohms.
Yeah, I kinda already knew the answer as soon as the question posted. Regulated supplies should be close to the load.
Every time I get the urge to build an external PSU for universal convenience and cost reduction, the cons outweigh the pros and the idea goes away again.
Every time I get the urge to build an external PSU for universal convenience and cost reduction, the cons outweigh the pros and the idea goes away again.
Long wiring defeats regulated supply advantage. Not entirely, as it would still be better than any unregulated supply, but it would be a waste of available performance.
I think that your solution with compact dual mono supply module, that can be transferred between different amplifiers is very good.