So voltage across R6 is now zero ?
and the voltage measured from C3 negative to R9 is now zero ?
R10 should still have the plus 22 volts on it.
and the voltage measured from C3 negative to R9 is now zero ?
R10 should still have the plus 22 volts on it.
Checking the transistor by the multimeter:
Base (red lead) - Col (black lead) - 0.866Ohm
Base (red lead) - Emmit (black lead) - 0.877Ohm
All the other combinations give me infinity.
So the transistor is OK?
Base (red lead) - Col (black lead) - 0.866Ohm
Base (red lead) - Emmit (black lead) - 0.877Ohm
All the other combinations give me infinity.
So the transistor is OK?
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Also checked that the leads are not mixed up. It's 100% true. I checked the legs of the transistor by the datasheet and the multimeter and then checked it's position on the PCB. There is a C B E printed on the board.
One step at a time 🙂
Those voltage readings are now correct.
Everything at this point is suggesting a problem with T1, maybe leaky. Let us see by checking further.
While the transistor is removed, measure the voltage across the base and emitter pads on the board. It should be zero. If it is, then there is a problem with T1
This isn't working is it... what do you want to do ?
I can't see any way you could have 9.8 volts on the base (and the emitter is at zero)
I can't see any way you could have 9.8 volts on the base (and the emitter is at zero)
hmm. How could it be possible it theory? I don't know what to do next.
So this board have the same problem as the first pcb?
So this board have the same problem as the first pcb?
I think you can see by looking at the circuit that there is no path available for any positive voltage to appear on T1 base. T2 emitter is at zero, T2 collector connects to the minus 22 volt supply and T2 base is effectively floating.
Where is it coming from ?
Where is it coming from ?
Do you think I do something wrong?
But I absolutely strict follow your instructions!
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I really don't know. These readings just don't make sense and we are spending a huge amount of time and just not getting any nearer.
This is a crazy thought, and clutching at straws here... are the boards a paxolin or paper type ? Could they have absorbed moisture, enough to make them slightly conductive. If you connect your meter to C3 negative and then press the other probe into the bare board around T1 does any voltage show up at all. Any at all. The board should be a perfect insulator but is it ?
Have to leave it for today. All very strange.
This is a crazy thought, and clutching at straws here... are the boards a paxolin or paper type ? Could they have absorbed moisture, enough to make them slightly conductive. If you connect your meter to C3 negative and then press the other probe into the bare board around T1 does any voltage show up at all. Any at all. The board should be a perfect insulator but is it ?
Have to leave it for today. All very strange.
I'm just going to add to that... remember when you changed C7 on the other board and it worked for a little while ? Soldering, heat drying moisture ?
Crazy I know but worth considering.
Crazy I know but worth considering.
Yes it worked for a little when I did something with the c2 cap but now it don't work at all. Very hard to understand it.
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That's right. Could the boards have absorbed moisture and so become all slightly conductive. That would play havoc with transistor biasing and explain crazy readings.
Its definitely worth you checking this out.
Its definitely worth you checking this out.
What the crazy board is it?
Look, I desoldered all the components going to this trace (c7 and r13). Now I have just the isolated trace on both side of the PCB and it has 24V now. How could it be possible? Visualy i don't see any connections to it!
Here it is
http://terrom.ru/pcb5.jpg
Look, I desoldered all the components going to this trace (c7 and r13). Now I have just the isolated trace on both side of the PCB and it has 24V now. How could it be possible? Visualy i don't see any connections to it!
Here it is
http://terrom.ru/pcb5.jpg
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