Ampeg B200R Bass Amp

[g1]

Ok, those results are radically different than what you posted before.
Should we trust the other measurements or do you think it would be wise to double check them all again?

[guitardad]

Find a local tech with a variac. I have loaned one of mine out a couple times. You can buy one with the $ you keep spending on parts. Bulb limiters are ok, but also can become an issue getting normal operation on some occasions. A variac you can run up slowly and check things before destroying new components.

OP circuits are balanced as many have said. You should essentially have maybe 40mv or less on the output at idle.

[robgrif]

ok the amp voltages are
q6 B -04.2 V C -44.6 V E -3.5 V BE RANGING .9V TO 50V
Q7 B +3.4 V C 45 V E 3.0 V BE RANGING .5 V TO 50 V
Q4 G +45 V D -43 V S +48 V GD +88V GS -4V
Q11 SAME AS Q4
Q5 G -45V D -43V S -48V GD -1.8 GC +4
Q8 SAME AS Q5
AMP IS ON 100 WATT limiter dim bulb
readings on q6 and q7 were inconsistent from one time to the next
so do these readings give any clue to a fault source for this amp
thanks for any thoughts you might have

[Jazz P Bass]

BE RANGING .9V TO 50V
Q7 B +3.4 V C 45 V E 3.0 V BE RANGING .5 V TO 50 V

I have no idea what this statement means. " BE RANGING .5 V TO 50 V"

[robgrif]

I have no idea what this statement means. " BE RANGING .5 V TO 50 V"

sorry for confusion of that statement . the base emitter voltage on q6 and q7 is not static it is constantly changing
from approx .9 v to approx 50v it is not staying at any particular voltage. thanks i hope this is clearer also -43 volts is appearing on drain of q4 and q11 making gate drain voltage 88 volts . just putting these numbers out there from circuit measurements to see if any of these values are expected or unexpected in this particular circuit
thanks for response

[g1]

Are you seeing any pulsing of the lamp? Are the supply voltages stable?
I don't see how the BE voltages should be fluctuating when measured B to E, but not when referenced to ground.
Maybe there is a board ground that is not connected because the board is out of the chassis?

[Jazz P Bass]

Is the preamp hooked up?

That header references the power supply chassis ground to the output board ground (Marked triangle 2)

[robgrif]

no pulsing in light. board in chassis. preamp / tube circuit are not hooked up .I will re-connect those items.

[robgrif]

ok preamp and tube section hooked up
new measurements
q5 and q8 g-52v d+3v s -52v
q4 and q11 g+50v d+3v s +52v
q6 be .6v
q7 be .5v
speaker output +3vdc

[Jazz P Bass]

Get Rid Of The Limiter.

[robgrif]

Get Rid Of The Limiter.

ok no limiter still 3vdc on speaker output

[Jazz P Bass]

Without sounding malicious, cranky or a wiseass:
Do you understand how this circuit functions?

You cannot throw voltages around & expect someone else to fix this amp.

Do a little more digging.
Look at the mosfet gates & try to decide why one is turning on enough to output 3 volts.
Is the polarity of the 3 volts +?
That is a sure fire hint.
End of rant.

[bsco]

There are lots of people here giving very good advice...reading through these posts should have narrowed down your problem...maybe you need to start fresh...it doesn't make any sense to keep installing parts and going around in circles.......what exactly is the state of the amp at this particular point??Are you still blowing mosfets??? if you are getting dc at the output there has to be something wrong in the output stage somewhere......either you have problems with the mosfets, the way they are mounted, etc....the drivers, or associated parts.....resistors, capacitors, diodes...you could even have problems with circuit traces.......so......what is the current condition of the amp at this moment....

[The Dude]

sorry for confusion of that statement . the base emitter voltage on q6 and q7 is not static it is constantly changing
from approx .9 v to approx 50v it is not staying at any particular voltage. thanks i hope this is clearer also -43 volts is appearing on drain of q4 and q11 making gate drain voltage 88 volts . just putting these numbers out there from circuit measurements to see if any of these values are expected or unexpected in this particular circuit
thanks for response

To quote my previous post, "If the voltage is the correct polarity from b to e on a transistor, the only way it can be more than .7 or so volts on a standard transistor is if the transistor is open/bad/defective."

When you made these measurements, was it with NO signal applied and volumes down? If not, try it again. These DC measurements should not change.

[Jazz P Bass]

The amp was not fully hooked up.
The last posting the OP hooked up the preamp & tube board.
So these readings probably settled down as there is now 'only' 3 Vdc on the output.