http://terrom.ru/125pcb3.jpg
look please here. There are some voltages printed on the PCB. What should I do with them? How to mesure it?
look please here. There are some voltages printed on the PCB. What should I do with them? How to mesure it?
in normal use lamp lit a very little at 16 speed little more on 33 and more on 45.
I have no normal state now and the lamp lit even more brighter...
I have no normal state now and the lamp lit even more brighter...
I've given this some thought and we need a different plan of attack on this so this is what I want you to do.
1/ We need to stop the excess current draw to be able to work and measure on the board without anything getting hot or drawing current. To do this you need to disconnect the motor so that the voltage comes back on C3.
2/ We are going to treat the circuit as a simple DC coupled amplifier (which it is) and see if we can find the problem by looking at the whole circuit as one. To do this you need to make sure that the circuit is complete and that all parts fitted back to the board.
3/ Set your meter to DC volts and connect the black lead to the junction of C2/C3. The black stays there for all the following measurements.
4/ I want you to copy and paste these measurement points and add your voltage readings.
T1 Emitter=
T1 Base =
T1 Collector =
T2 Emitter =
T2 Base =
T2 Collector =
T3 Emitter =
T3 Base =
T3 Collector =
T4 Emitter =
T4 Base =
T4 Collector =
T5 Emitter =
T5 Base =
T5 Collector =
T6 Emitter =
T6 Base =
T6 Collector =
T7 Emitter =
T7 Base =
T7 Collector =
1/ We need to stop the excess current draw to be able to work and measure on the board without anything getting hot or drawing current. To do this you need to disconnect the motor so that the voltage comes back on C3.
2/ We are going to treat the circuit as a simple DC coupled amplifier (which it is) and see if we can find the problem by looking at the whole circuit as one. To do this you need to make sure that the circuit is complete and that all parts fitted back to the board.
3/ Set your meter to DC volts and connect the black lead to the junction of C2/C3. The black stays there for all the following measurements.
4/ I want you to copy and paste these measurement points and add your voltage readings.
T1 Emitter=
T1 Base =
T1 Collector =
T2 Emitter =
T2 Base =
T2 Collector =
T3 Emitter =
T3 Base =
T3 Collector =
T4 Emitter =
T4 Base =
T4 Collector =
T5 Emitter =
T5 Base =
T5 Collector =
T6 Emitter =
T6 Base =
T6 Collector =
T7 Emitter =
T7 Base =
T7 Collector =
This is what I would expect aproximately... and we are looking for big differences in your readings
T1 Emitter= 0.04
T1 Base = 0.6
T1 Collector = 21.9
T2 Emitter = 0.04
T2 Base = minus 0.2
T2 Collector = minus 22
T3 Emitter = 22
T3 Base = 21.3
T3 Collector = 0.06
T4 Emitter = minus 0.6
T4 Base = around zero.
T4 Collector = 22
T5 Emitter = minus 0.06
T5 Base = minus 0.01
T5 Collector = 21.4
T6 Emitter = 22
T6 Base = 21.9
T6 Collector = 0.04
T7 Emitter = 0.04
T7 Base = 0.04
T7 Collector = minus 22
T1 Emitter= 0.04
T1 Base = 0.6
T1 Collector = 21.9
T2 Emitter = 0.04
T2 Base = minus 0.2
T2 Collector = minus 22
T3 Emitter = 22
T3 Base = 21.3
T3 Collector = 0.06
T4 Emitter = minus 0.6
T4 Base = around zero.
T4 Collector = 22
T5 Emitter = minus 0.06
T5 Base = minus 0.01
T5 Collector = 21.4
T6 Emitter = 22
T6 Base = 21.9
T6 Collector = 0.04
T7 Emitter = 0.04
T7 Base = 0.04
T7 Collector = minus 22
T1 Emitter=22.0
T1 Base =21.35
T1 Collector =21.85
T2 Emitter =20.4
T2 Base =20.9
T2 Collector =-22.5
T3 Emitter =21.2
T3 Base =21.9
T3 Collector =21.7
T4 Emitter =10.6
T4 Base =10.10
T4 Collector =21.75
T5 Emitter =8.4
T5 Base =10.10
T5 Collector =21
T6 Emitter =21.5
T6 Base =21.7
T6 Collector =20.8
T7 Emitter =20.65
T7 Base =20.8
T7 Collector =-22.22
T1 Base =21.35
T1 Collector =21.85
T2 Emitter =20.4
T2 Base =20.9
T2 Collector =-22.5
T3 Emitter =21.2
T3 Base =21.9
T3 Collector =21.7
T4 Emitter =10.6
T4 Base =10.10
T4 Collector =21.75
T5 Emitter =8.4
T5 Base =10.10
T5 Collector =21
T6 Emitter =21.5
T6 Base =21.7
T6 Collector =20.8
T7 Emitter =20.65
T7 Base =20.8
T7 Collector =-22.22
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That's great 🙂
That shows one possible problem but we might need to look a bit closer.
T5 with the base at 10.10 and the emitter at 8.4 volts. On the face of it there is a problem with T5 because you can't have more than around 0.7 volts across the base/emitter junction (it behaves like a diode with a 0.7 volt drop).
So there could be a problem with T5. Do you have a replacement you can fit ?
That shows one possible problem but we might need to look a bit closer.
T5 with the base at 10.10 and the emitter at 8.4 volts. On the face of it there is a problem with T5 because you can't have more than around 0.7 volts across the base/emitter junction (it behaves like a diode with a 0.7 volt drop).
So there could be a problem with T5. Do you have a replacement you can fit ?
More... just looking a bit more at your readings.
T4 and T5 emitters are joined and yet you are seeing different voltages on each. Check the continuity between T4 emitter and T5 emitter.
T4 and T5 emitters are joined and yet you are seeing different voltages on each. Check the continuity between T4 emitter and T5 emitter.
The voltage is jumping so the readings changed. T4 and T5 has a good linkage...
T4-5 emitters have the same voltage
T4-5 emitters have the same voltage
OK. Lets carry on then with what we have.
Here is the plan 🙂
As the readings are in doubt (jumping) I think we have to replace T4 and T5 to simply eliminate them from the problem.
If that doesn't achieve anything then we 'break' the oscillator feedback network to see if the jumping readings stabilise. We should be able to do that by simply removing the bulb.
Having done that, recheck the voltages.
The high voltage on T5 base is a definite clue. It should be nearly zero because it is tied to ground via R24. So check around there. Make sure that R24 goes to the base of T5 and that the other end goes to ground. Make sure R24 isn't open. Make sure there are no shorts or anything conductive that could be putting voltage on T5 base.
If you remove T5 completely then there must be 0 volts on the point where the base goes. If we are still struggling at this point then do this check. Remove T5 and check the base voltage is absolutely zero. It must be because its tied via R24 to ground.
I'll look in later and see how you are getting on.
Here is the plan 🙂
As the readings are in doubt (jumping) I think we have to replace T4 and T5 to simply eliminate them from the problem.
If that doesn't achieve anything then we 'break' the oscillator feedback network to see if the jumping readings stabilise. We should be able to do that by simply removing the bulb.
Having done that, recheck the voltages.
The high voltage on T5 base is a definite clue. It should be nearly zero because it is tied to ground via R24. So check around there. Make sure that R24 goes to the base of T5 and that the other end goes to ground. Make sure R24 isn't open. Make sure there are no shorts or anything conductive that could be putting voltage on T5 base.
If you remove T5 completely then there must be 0 volts on the point where the base goes. If we are still struggling at this point then do this check. Remove T5 and check the base voltage is absolutely zero. It must be because its tied via R24 to ground.
I'll look in later and see how you are getting on.
I changed r24 with the other resistor. No result. I also couldn't see any problems around here.
10 volts dc on the base of T5 is a big problem. We must find out why that is present.
Remove T5 and measure the voltage where the base connects. It must be zero volts)
Remove T5 and measure the voltage where the base connects. It must be zero volts)
I removed all 3 BC171B (T1, T4, T5) with the new BC147A. Result is the same. Now will check the voltages.
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No, leave T5 out and measure the voltage at the output (the voltage on R9). That voltage should have flipped from plus 20 to become minus 20 without T5 fitted.
That doesn't compute 😀
With T5 removed there must always be no voltage on the base. Nothing in the rest of the circuit can affect that result. It must be zero.
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