eheheheh... sorry if I ruin your language and thanks for the correction
By the way voltages in the working channel are R23 2.25V, R24 2.38V
No hurry don't worry
No problem
Those voltages sound OK and agrees with the indicated 9ma marked on the diagram. What about the bad channel ? but this 56 volts is the real problem.
Something seriously amiss with that. The output stage should have exploded with that kind of bias... and it hasn't.
Measure and record these voltages in the same way. You are measuring across points A and A- (which is the 56 volts you measured... recheck it and be sure) and then B to B- and C to C- and D to D-
So one meter lead on B and the other lead on B- and read the result. Then do the same for C and C- and D and D-
Maybe one of the drivers or pre drivers is open circuit but you need to be extremely careful measuring. If any transistor has more than 0.8 volts across its base and emitter then its faulty. That's a good check on those four transistors and worth doing but remember one slip of the meter and it all goes up.
I'll take a closer look later. Many of the readings are strange and we need to be 100% certain on them.
For example (just do a recheck on this), Q7 with 0 volts B-E. Yet the volt drop across R23 is 3.6 volts. That means 13 milliamps is flowing through R23 and Q7 and yet Q7 is OFF with zero volts across its base and emitter. On that basis its faulty but I suspect not. Just recheck that result We have to be sure.
Its unlikely to be a problem in that area anyway but the readings are so "all over the place" that we need to be sure.
For example (just do a recheck on this), Q7 with 0 volts B-E. Yet the volt drop across R23 is 3.6 volts. That means 13 milliamps is flowing through R23 and Q7 and yet Q7 is OFF with zero volts across its base and emitter. On that basis its faulty but I suspect not. Just recheck that result
We have to be sure.Its unlikely to be a problem in that area anyway but the readings are so "all over the place" that we need to be sure.
I mean one lead on A and one on A- Then measure and write down the result. Then do the same for B and B- by putting one lead on B and the other on B- and again write down the result. Do that for C and D also. Four readings in total
P.S.
Get some nice grabber clips to make your measurements, using standard probe leads can result in disaster as you have found out previously. Turn power off, make connections with grabbers, turn power back on, measure. It is so easy to lose connection when holding a probe and then moving your eyes to look at the meter.
Good luck
Rick
Get some nice grabber clips to make your measurements, using standard probe leads can result in disaster as you have found out previously. Turn power off, make connections with grabbers, turn power back on, measure. It is so easy to lose connection when holding a probe and then moving your eyes to look at the meter.
Good luck
Rick
I mean one lead on A and one on A- Then measure and write down the result. Then do the same for B and B- by putting one lead on B and the other on B- and again write down the result. Do that for C and D also. Four readings in total
ehehehe... I meaned I don't understand what's A and A- stand for (same thing with the other letters), sorry I know this probably shoud be easy by I'm quite nooby
Rsavas:
I'm using alligator clips for measuring, errors are more related to the operator
I'm sorry, my mistake. Did I not attach the diagram. I've deleted it too... I'll do it again.
That 6.5 ohm reading may be down to your meter and its added lead resistance. But something is very wrong with that voltage reading so lets pursue it.
Can you measure the voltage at the other side of those resistors. That's between pins 18 and 20. In other words between the bases of the output transistors.
Can you measure the voltage at the other side of those resistors. That's between pins 18 and 20. In other words between the bases of the output transistors.
Those resistors are going to be OK. Measuring low values can be problematic sometimes.
What you need to measure now is the voltage across points 18 and 20 (that is measuring between the bases of the output transistors). I've marked it E and E-
You measured 9.5 volts between D and D- so something is very wrong around this area of the circuit.
What you need to measure now is the voltage across points 18 and 20 (that is measuring between the bases of the output transistors). I've marked it E and E-
You measured 9.5 volts between D and D- so something is very wrong around this area of the circuit.
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.