Hi to all,
a friend of mine, has a couple of PM 845 Melody but the audio is very bad.
We think about Bias setting but I can't found the service manual to measure and setting the bias.. Someone can help me ??
Thank you in advance.
a friend of mine, has a couple of PM 845 Melody but the audio is very bad.
We think about Bias setting but I can't found the service manual to measure and setting the bias.. Someone can help me ??
Thank you in advance.
Hi Spippolone,
Seems there's no service manual available online. I think you may check the B+, plate resistor, and the voltage between Grid and Cathode of each stage. Then, we can estimate if the tubes are biased correctly.
It would be great if you can trace the circuit and share the schematic with us.
Regards,
Johnny
Seems there's no service manual available online. I think you may check the B+, plate resistor, and the voltage between Grid and Cathode of each stage. Then, we can estimate if the tubes are biased correctly.
It would be great if you can trace the circuit and share the schematic with us.
Regards,
Johnny
According to the manual found on their website:
Adjust the tube current switch. It is used to adjust the current of output power transistor 845, and each 845 tube is adjusted to 60~65mA.
So twiddle the adjuster until the meter reads 60 - 65 ma.
Adjust the tube current switch. It is used to adjust the current of output power transistor 845, and each 845 tube is adjusted to 60~65mA.
So twiddle the adjuster until the meter reads 60 - 65 ma.
Thank you to all ..
the PM 845 MAX have the meter and the bias tune, bus I have discovered that the PM 845 (no max, the old model) don't have meter and it has not bias tuning.
I went to my friend's house, after listen the audio was not bad.. how he told me, but is very very very low with the volume to the max position.
I assumed in my head that was a shor circuit on the audio signal.
I have do an investigation, but someone has replaced the balance cannon connector, and
I thing that he made a wrong connection. I will go to deassembly it and I will update you.
the PM 845 MAX have the meter and the bias tune, bus I have discovered that the PM 845 (no max, the old model) don't have meter and it has not bias tuning.
I went to my friend's house, after listen the audio was not bad.. how he told me, but is very very very low with the volume to the max position.
I assumed in my head that was a shor circuit on the audio signal.
I have do an investigation, but someone has replaced the balance cannon connector, and
I thing that he made a wrong connection. I will go to deassembly it and I will update you.
Hi the picture posted to Extreme_Boky is referred to a PM845 MAX, I have worked on PM 845
and I solved...
The problems were some welds.. and a very poor input selector. I have replace the input selector and redone some weldings
It is very incredible in an this level amplifier...
Thank you to all
and I solved...
The problems were some welds.. and a very poor input selector. I have replace the input selector and redone some weldings
It is very incredible in an this level amplifier...
Thank you to all