Received this amp... Output Stage damaged.. No Fets inside. Drive Board one mpsa 56 was burned and the 220ohm resistor..
Problem is now,That If Input the Driver Card in place,without mosfets, the 220 ohm directly Starts burning...cant find the Problem.
Problem is now,That If Input the Driver Card in place,without mosfets, the 220 ohm directly Starts burning...cant find the Problem.
Attachments
I replaced all Transistors in the middle row. even if they measured ok... All other transistors on the board i have removed too, and checked them. All ok.
Without driveboard, i have a current draw from 1.67Amps, with board inside 2.6Amps... Checked all solder points for the output fets, and also the diodes ...
Q123 been defect in the beginning. MPSA 56
Without driveboard, i have a current draw from 1.67Amps, with board inside 2.6Amps... Checked all solder points for the output fets, and also the diodes ...
Q123 been defect in the beginning. MPSA 56
To try to find where the current is going, measure the DC voltage directly across R180, R182 and R184 and post the voltages.
i was able to make a quick read...R 184 0Volt, R182 0.5Volt R180 0,5V.
After that, short q127, q126, C126 starts smoking again.
After that, short q127, q126, C126 starts smoking again.
The resistor is marked with C126. But there was a 220Ohm resistor inside before... I will try it out tomorow, because i have to change the broken transistors before.
So,
Q126 shorted
Removed Q127 and Q126
Resistor C191 starts smoking again. ( Should there be a resistor? Because C191 suggest me a capacitor)
Removed C191, R190 starts smoking.
Measured voltage accros R122 its 85V
Q126 shorted
Removed Q127 and Q126
Resistor C191 starts smoking again. ( Should there be a resistor? Because C191 suggest me a capacitor)
Removed C191, R190 starts smoking.
Measured voltage accros R122 its 85V
Replaced all Transistors at the Drive board. used ice Spray for visible Heat... Q125 get hot very quick.. Strange,all voltages are correct at the Board.. No short at the fet Pads..