ok no limiter still 3vdc on speaker output
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ok no limiter still 3vdc on speaker output
ok preamp and tube section hooked up
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
no pulsing in light. board in chassis. preamp / tube circuit are not hooked up .I will re-connect those items.
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....
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...
ok thanks probe + on emitter - on base q6=+.6 v probe +on emitter - on base q7 = -.45 v
ok removed limiter 1 amp fuse no speaker 3.5 volts dc on output terminals this does not change with bias adjustment fuse blew while I was adjusting bias. installed new one amp fuse . still 3.5 volts...
Okay hi all parts arrived put in 4 new mosfets. The amp is working on limiter right now. Bulb is dim. Measuring 1.0 volts dc on speaker output. Preamp output working.touched. Small 8 ohmns speaker to...
ok thanks will return as soon as new parts arrive
happy thanksgiving to all those celebrating
thanks for all input lots of thought thanks
anyway i think JAZZ p Bass is on to something about the limiter upsetting things. put new mosfets in 60 watt limiter glowing bright .Installed preamp...
thanks for the info .
all those gate diodes test good . all the outputs were changed as were pre-drivers and were good. all resistors test good correct ohmns readings. the preamp board is not...
ok installed fuse it blew also both mosfets q5 and q8 blew as well oops fuse was 2amp my bad
any way this is the same problem originally so whatever it is remains a mystery i will purchase two new...
ok thanks something strange is happening.when the emitter of q7 is touched with + probe from meter light limiter dims amp starts to hum and dc on speaker goes to -47 volts. i have two meters this...
checked the resistors they are all correct values and good
as for q6 and q7 not sure what is happening there.
[QUOTE=The Dude;367281]It would appear from your measurements that Q6 and Q7 are open. Also check R41, R43, R58, and R67.[
ok checked those resistors all good
ok thanks here are the values that I got
Q7 E=+.06 v C=+18v B=+3.16v
Q6 E=-.06 v C=-18v B=-2.6v
Q3=E 2.6v C=3.16v B=1.5 v
U3 ouput = 0v
light bulb limiter 60 watt bulb
ok replaced power supply caps one was causing more current to flow when touched.still drawing excess current. would it be possible for U3 to be causing this problem.?just guessing now.
Sorry wrong meter scale. Reading is 49.5 milivolts dc . On. 33 ohmns resistors
20.7 @source q8 20.8 source @q11
There is 49.5 milivolts through them I tried to adjust it down but it did not go lower the bias pot measures 500 ohmns and responds to adjustment down to zero.
Okay replaced all those bits however amp still pulling high current on light bulb limiter. Not sure what else could be drawing current power amp is only board hooked with nothing attached. The last...
the part is an in rush current limiter that failed . identified by J.M.Fahey (thanks) it is an sl22 1000r .still passes ac to amp
q5 and q8 removed 60 watt light bulb limiter showing low idle...
here is jpeg of power amp 31574
and power supply31575
thanks very much for advice and schematics.
this amp failed about one year ago with same problem i think but ithought the cause was the incorrect factory board wiring of crossover
is it possible...
thanks speaker not connected
no ac at speaker terminals
btw acdc rocks
ok thanks for that . just going slow removed q8 . limiter 60 watt bulb barely glowing
should i continue to remove other two mosfets
would this be all that is wrong or could there be underlying...
thanks for reply
schematic does not show MOV it is on black supply line before fuse a piece of the device broke off when problem occured. also transformer has same wires as figure for export 240...
I have an Ampeg B200r Bass Amp with a problem
Stopped working, speaker started humming seems to be drawiing excessive current MOV blew out and fuse was sparking but did not blow fuse The...