Hello all!
I have a punch 50m mono amplifier on my talbe which is working, but sometimes has little problems.
I want to start troubleshooting but i dont have the schematics and i hope somebody has it?
The board # is: " PC-1041-E "
When powering up the amp, sometimes it idles fine and produces clean audio with 1.3 amps of idle current and 30mV DC on speaker terminal. Turning bias pot is possible with idle current change. No problems occur, everything is fine.
After several times of powering up the amp there is a problem now : it only idles at 1.1 amps , has around 1 V DC on the Speaker terminals. Turning the bias pot in this case has no effect, not even full cw.
driving a sinus signal into the amp shows problems on the speaker terminal. With more gain the positive half of the waveform starts to clip very strong.
I noticed that Q106 and Q 107 get hot, these are MPSA56 directly under the bias pot.
Opamps have positive and negative Supply voltage.
Without a shematic i feel a little bit lost, especially because there is one SMD Resistor without marking, its mounted Upside down " R128 ", seems its from factory, amp shows no signs of Repairs.
Is this amp similar in the shematics like the punch 250M?
I hope somebody can help, its a nice amp with good low impedance capabilities.
Best regards
Andi
I have a punch 50m mono amplifier on my talbe which is working, but sometimes has little problems.
I want to start troubleshooting but i dont have the schematics and i hope somebody has it?
The board # is: " PC-1041-E "
When powering up the amp, sometimes it idles fine and produces clean audio with 1.3 amps of idle current and 30mV DC on speaker terminal. Turning bias pot is possible with idle current change. No problems occur, everything is fine.
After several times of powering up the amp there is a problem now : it only idles at 1.1 amps , has around 1 V DC on the Speaker terminals. Turning the bias pot in this case has no effect, not even full cw.
driving a sinus signal into the amp shows problems on the speaker terminal. With more gain the positive half of the waveform starts to clip very strong.
I noticed that Q106 and Q 107 get hot, these are MPSA56 directly under the bias pot.
Opamps have positive and negative Supply voltage.
Without a shematic i feel a little bit lost, especially because there is one SMD Resistor without marking, its mounted Upside down " R128 ", seems its from factory, amp shows no signs of Repairs.
Is this amp similar in the shematics like the punch 250M?
I hope somebody can help, its a nice amp with good low impedance capabilities.
Best regards
Andi
