Hey guys I have a punch 301m I'm trying to fix. The problem is power supply was shorted. I put in two mosfets for testing I get 4.45 volts on all four gate pads. As soon as power is applied C6 & C5 & C20, C22 get warm and draws a lot of current.
The transformer may be defective. Pull the rectifiers and try powering it up again.
Do you have a scope?
Do you have a scope?
I don't have one unfortunately. is there a reason why it sparks when I touch the terminals with the wires just only B+ and GND no remote and with fets installed. It sparks when I touch the connections.
It's going to spark some because the rail caps are charging. If it sparks intensely every time, there is another problem.
Does it draw significant current when you connect both B+ and ground? Is the high current draw constant or just for a fraction of a second?
Does it draw significant current when you connect both B+ and ground? Is the high current draw constant or just for a fraction of a second?
Yes it sparks every time I touch the terminals on the amp no remote hooked up and there's no fets installed. There's no high current draw when + & - is applied. I noticed a really high current draw when I put in two fets for testing those capacitors were getting warm. I double checked the gate pads Q7 & Q15 have 6.55 volt while the the other two have 4.45 volts. Any ideas? Should I remove the rectifiers and try again?
Replaced all of the driver transistors same problem. I removed C6 & C5. I applied power one of the two test transistors gets really hot in a matter of seconds amp will turn on but can't keep it on no longer than 5 secs with out the transistor burning out. Is it possible the rectifiers are shorted?
No. All of them are measuring out the same no 4.5 volts. I also removed the rectifiers but the amp won't turn on.
With the rectifiers removed, the power supply FETs installed and all power connections used, do the power supply FETs still heat up?
Do you read 0 ohms to ground from leg 3 to ground for all power supply FETs?
Do you read 0 ohms to ground from leg 3 to ground for all power supply FETs?
Okay so took out the original rectifiers and put in some new replacements powered the amp back on no excessive current draw or power supply fets heating up. Do you think one of them was causing the problem? Also Which way does the rail caps go in? Like the polarity?
Actually no. You what it was as a matter of fact As I was looking at a pictured I took of the board previously it appears who ever had this amp installed the rail caps backwards because I took them out thinking it was the caps or rectifiers. After I put in new rectifiers and installed two IRF3205's for testing amp powered up and produced audio.. So my guess was the capacitors all this time installed incorrect I remember it would draw excessive current and the power supply fets would heat up in seconds.. Well this one is fine for now... Thanks perry
What parts you use for driver transistors in the power supply area? I've ran out got another punch amp to fix its a 125.2
I use the MMBTA06 and MMBTA56 but they're no better than the MMBT3904 and MMBT3906 originals. I generally just have those on the bench.
Start a new thread if you need help with a different amp.
Start a new thread if you need help with a different amp.
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