Sorry to spoil your party but without proper tooling your path is limited - you will never see a thing like this:
So with bulb tester in place, you have restored connections to output devices? And Q1 and Q4 collector voltages are now near ground?
If so, then bias spreader is now the focus. What is collector to emitter voltage across Q8? It may be time to navigate from the SM schematic rather than the sim schematic.
If so, then bias spreader is now the focus. What is collector to emitter voltage across Q8? It may be time to navigate from the SM schematic rather than the sim schematic.
BSST, your suggestions are so accurate,
Q1,4 voltage varies in the rhythm of the light bulb from 1 to 4V,
Across Q8 from 0,3 to 1V.
It looks like the amp wants to start when sufficient bias voltage appears, consumes the current and the bulb kills the current. I don't have 200W bulb, possibly this model needs higher current for starting up.
Both of the channels act the same, the voltages varying across the spreader are likely the same.
Q1,4 voltage varies in the rhythm of the light bulb from 1 to 4V,
Across Q8 from 0,3 to 1V.
It looks like the amp wants to start when sufficient bias voltage appears, consumes the current and the bulb kills the current. I don't have 200W bulb, possibly this model needs higher current for starting up.
Both of the channels act the same, the voltages varying across the spreader are likely the same.
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Most probably so. You just need to pinpoint the culprit i.e. element consuming the current.
A small 8,6 kg amplifier should not need 200W bulb in DBT - something else is wrong elsewhere.
Do both channels behave similarly?
You might consider removing the supply connections to the output transistors to one channel, as you had earlier. This might reduce the Dim Bulb current fluctuations and foster troubleshooting of the remaining channel. Examine if adjusting bias pot changes spreader voltage and voltage drops across the 0.22 ohm emitter resistors. Swap experiment to opposite channel if appropriate. Again, no applied loads.
You might consider removing the supply connections to the output transistors to one channel, as you had earlier. This might reduce the Dim Bulb current fluctuations and foster troubleshooting of the remaining channel. Examine if adjusting bias pot changes spreader voltage and voltage drops across the 0.22 ohm emitter resistors. Swap experiment to opposite channel if appropriate. Again, no applied loads.
Thanks, again clever,
But during the measurings I possibly made a short or something another fried and now there's no light fluctuation, all of opts have -14V at the bases and rails went down to -/+ 14V
Tomorrow I will investigate more
But during the measurings I possibly made a short or something another fried and now there's no light fluctuation, all of opts have -14V at the bases and rails went down to -/+ 14V
Tomorrow I will investigate more