MPSA42.
Hi Sir,
May i know what is Q116, Q118 and Q129A?
The amp is trying to come on but going into protect. it keeps cycling. and no oscillations on outputs. Do you have schematic by chance?
This is the basic circuit but the one in your amp has independent driver power supplies. See if this helps.
Generic Asian Clone driver board RE and Clone
The photos I have don't show the face of the transistors you need.
Generic Asian Clone driver board RE and Clone
The photos I have don't show the face of the transistors you need.
Hi Sir,
May i know what is Q116, Q118 and Q129A?
Attachments
Pull the driver board. What's the resistance from the gate to the source for the outputs? They should read all the same.
all have about 4.73kohms
Will it power up without the driver board?
Yes without driver board it comes on good. No problem.
I found some notes on this amp. Q116 on the driver board and Q140 on the main board were causing the amp to go into protect.
I changed both the transistors and it is still going into protect and trying to come on then protect.
Is there any DC across the speaker terminals when it tries to power up?
No dc wgen it is trying to start. After i change those transistors it is going straight to protect and not even trying to come on.
If it's doing something different, something changed. The new transistors are wrong, the old ones were defective and now another problem is causing the fault, maybe a solder bridge or a bad connection?
Do you have any schematic for this amp? Without that is very hard to find bad connections.
Not specifically for this amp. Are there opto-couplers under the driver board?
Yes it have one optocoupler under the driver board.
Sometimes the sockets get lose and don’t make full contact with the pins on the driver board . And this is what cause’s the amp to go into protection
Try plugging the driverbiars back in and twist is slightly to the right and hold it there and then try powering it up see if that helps .
I have seen several of these amps so this
Try plugging the driverbiars back in and twist is slightly to the right and hold it there and then try powering it up see if that helps .
I have seen several of these amps so this
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