OK, lets work with that. And this is measuring from the emitter of Q321 as I outlined above.
And:
Look at the circuit. If you have 28 volts present on both legs of the 0.22 ohm then you should have 28 volts on the emitter of Q325. Do you agree? The emitter goes to the 0.22 ohm and yet you say 'the rest' are zero.
If you had 28 volts on just one leg of the 0.22 ohm and nothing on the other leg then the 0.22 ohm would be open circuit.
Does that make sense?
I really feel is getting outside your comfort zone tbh 🙂
I agree with you. Looking at the circuit as you said if 28vdc is present at the .22 ohm resistors then there has to be 28vdc on the emitter of 325. I reasoned that the 28vdc is a result of an open resistor. Sure enought 2 of the .22 ohm resistors were open. I replaced them and now we have alot different voltages at 321 and 325. Although that is apparently working to a certain degree but the relay does not engage. The relay however clicks after I power off in a 10 second span
I get 1.8vdc across Q311.
Using the junction of .22ohm resistors as a reference the following are present.
Q319
E = -.62vdc
C= 100vdc
B= 400mv
Q321
E=383mv
C=.8mv
B=94mv
Q325
E=.2mv
C=.8mv
B=93mv
Using the junction of .22ohm resistors as a reference the following are present.
Q319
E = -.62vdc
C= 100vdc
B= 400mv
Q321
E=383mv
C=.8mv
B=94mv
Q325
E=.2mv
C=.8mv
B=93mv
I figured out why the relay was clicking. We had left Q331 out part of the protection circuit. I reconnected it and no more clicking after powering off
All those new readings show you now have a DC offset fault. Q319 collector at 100 volts implies all the other points are at what would be -50 volts if measured from ground.
With 0.22 ohms replaced we have to switch where we measure from and see what is going on with the offset. So using ground as the meter reference this time just check that the DC offset (voltage at the 0.22 ohm junction) is in fact now sat at -50 volts.
I suspect you have multiple issues with this amp which is why it might seem difficult to fix.
With 0.22 ohms replaced we have to switch where we measure from and see what is going on with the offset. So using ground as the meter reference this time just check that the DC offset (voltage at the 0.22 ohm junction) is in fact now sat at -50 volts.
I suspect you have multiple issues with this amp which is why it might seem difficult to fix.
it will be a bit before i get to it.We had a major winter storm come thru and I have to dig some snow out of the sidewalks
100mv offset is fine at this point. The rails will alter with a bulb and if the bias current alters in the good channel to that rail variation is likely normal
I've no quick way to diagnose the high negative offset as it could be caused by many things.
I think you are going to have to do as I suggested earlier and list all the transistor voltages just like you have done above. Also make sure the 16 volt supply is on one end of R307. I know it seems a lot of work but it might show something. The action of the feedback loop means there should be a massive error somewhere as the loop tries to correct the offset and tries to turn on the upper NPN section.
I've no quick way to diagnose the high negative offset as it could be caused by many things.
I think you are going to have to do as I suggested earlier and list all the transistor voltages just like you have done above. Also make sure the 16 volt supply is on one end of R307. I know it seems a lot of work but it might show something. The action of the feedback loop means there should be a massive error somewhere as the loop tries to correct the offset and tries to turn on the upper NPN section.
Do I use the the .22 ohm resistors as my reference point. And there is 16vdc on one side of R307
Q327
E=2.1mv
C=103 vdc
B=4.0mv
Q319
E=155mv
C=96vdc
B=401mv
Q323
E=4.5mv
C=96vdc
B=155mv
Q311
E=.831vdc
C=317mv
B=.782vdc
Q325
E=.2mv
C=.7mv
B=92mv
Q321
E=78mv
C=.6mv
B=380mv
Q329
E=30mv
C=18mv
B=92mv
E=2.1mv
C=103 vdc
B=4.0mv
Q319
E=155mv
C=96vdc
B=401mv
Q323
E=4.5mv
C=96vdc
B=155mv
Q311
E=.831vdc
C=317mv
B=.782vdc
Q325
E=.2mv
C=.7mv
B=92mv
Q321
E=78mv
C=.6mv
B=380mv
Q329
E=30mv
C=18mv
B=92mv
Sorry I missed your message, using resistors as a reference, I can go theu them again if you like
It has to be from ground really and its all the transistors so that is 16 of them. That's why I said it might seem like a lot of work but without seeing them set out its impossible to see what is going on.
I'll look in again tomorrow.
I'll look in again tomorrow.
Q327
e=-47vdc
b= -46vdc
c=49vdc
Q319
E=-47vdc
C=49vdc
B=-46vdc
Q323
E=-47vdc
C=50vdc
B==47vdc
Q311
E=-46vdc
C=-47vdc
B=-47vdc
Q325
E=-47vdc
C=-47vdc
B= -47vdc
Q321
E=-46vdc
C=-47vdc
B=-47vdc
Q329
E=-47vdc
C=-47vdc
B=-47vdc
This whole side seems to be -47vdc.
e=-47vdc
b= -46vdc
c=49vdc
Q319
E=-47vdc
C=49vdc
B=-46vdc
Q323
E=-47vdc
C=50vdc
B==47vdc
Q311
E=-46vdc
C=-47vdc
B=-47vdc
Q325
E=-47vdc
C=-47vdc
B= -47vdc
Q321
E=-46vdc
C=-47vdc
B=-47vdc
Q329
E=-47vdc
C=-47vdc
B=-47vdc
This whole side seems to be -47vdc.
