With no output fets the rail voltage is 48v where the 640's are and 52v where the 9640's go. When I put the fets in I have 100v where the 640's go and 0 where the 9640's go. Any ideas why this is happening?
Have you done basic troubleshooting, checking gate resistors, driver transistors...?
Have you ever worked on an amp of this design (output taken from center of the transformer)?
Have you ever worked on an amp of this design (output taken from center of the transformer)?
Yes this is the last of 3 I'm repairing. The first 2 were pretty straight forward. I spent more time on the mesha boards then anything else.
I replaced all the burnt resistors and few transistors. I was thinking of just replacing all of the driver transistors on the board hoping to get lucky.
My knowledge of class a or class a/b is nonexistent. With Rockford amps I usually blindly replace the drive circuit and that has worked for me everytime until now
I replaced all the burnt resistors and few transistors. I was thinking of just replacing all of the driver transistors on the board hoping to get lucky.
My knowledge of class a or class a/b is nonexistent. With Rockford amps I usually blindly replace the drive circuit and that has worked for me everytime until now
Connect a jumper between the collector and emitter of Q11.
Lift Dx05 and Dx07.
Set the bias pots fully CCW.
Power the amp up. Does it try to draw excessive current?
Lift Dx05 and Dx07.
Set the bias pots fully CCW.
Power the amp up. Does it try to draw excessive current?
You can't use the voltage in the output section to troubleshoot with any parts inside the servo loop missing, so yes.
Did it start drawing current because of the meter or did it start drawing current for no apparent reason?
Did you allow the rail caps to drain to see if if the same thing (no current draw then excessive current draw) happened again?
Did you allow the rail caps to drain to see if if the same thing (no current draw then excessive current draw) happened again?
Honestly idk. I took the reading and a few moments later I could smell the heat and looked at my ps and it was drawing 7 or 8 amps. I checked again after a few minutes and its still drawing too much current.
You have to replace them and recheck the drive components to get back to the conditions in post 11. You HAVE to monitor the temperature of the heatsink mounted components when testing. Setting the bias fully CCW generally prevents current flow through them but not always.
Is the DC the same on both channels?
If you touch a load across the output, does the DC drain off or does it try to pull excessive current?
If you touch a load across the output, does the DC drain off or does it try to pull excessive current?