Here's the fault details my amp was getting.
Strong buzz from both speakers, that got weaker the more the amp was left on, and didn't change with the volume control.
Pressing the "Direct" button reduced the hum by under half.
Loudness button didn't effect it.
You get this whatever input is selected, and it doesn't matter if something is connected to it or not.
Pressing "Tape Monitor" makes the tone a bit deeper. Maybe a bit louder too. Balance hardly changes it, and the bass and treble have a very slight effect.
It doesn't matter which set of speaker outputs you use, it will be the same.
The sound quality when playing anything is still good, and at higher volumes the buzz disappears into the background.
I replaced the two big capacitors on the main board, but this didn't change it. I searched this forum as good as I could using Google (search system on site suspended at present), and didn't find anything. I did get some information from another forum that put me on the right track.
I replaced C613, and C614 (470uF, 25V) and this has cured the hum. I believe these are the smoothing capacitors for the 15V circuit.
I did download a Service Manual with schematics from another site, but it was so bad I couldn't read the writing. If anyone has a link to a good copy, it would be nice to have it.
Please see attached pictures to help.
Regards, Rob
Strong buzz from both speakers, that got weaker the more the amp was left on, and didn't change with the volume control.
Pressing the "Direct" button reduced the hum by under half.
Loudness button didn't effect it.
You get this whatever input is selected, and it doesn't matter if something is connected to it or not.
Pressing "Tape Monitor" makes the tone a bit deeper. Maybe a bit louder too. Balance hardly changes it, and the bass and treble have a very slight effect.
It doesn't matter which set of speaker outputs you use, it will be the same.
The sound quality when playing anything is still good, and at higher volumes the buzz disappears into the background.
I replaced the two big capacitors on the main board, but this didn't change it. I searched this forum as good as I could using Google (search system on site suspended at present), and didn't find anything. I did get some information from another forum that put me on the right track.
I replaced C613, and C614 (470uF, 25V) and this has cured the hum. I believe these are the smoothing capacitors for the 15V circuit.
I did download a Service Manual with schematics from another site, but it was so bad I couldn't read the writing. If anyone has a link to a good copy, it would be nice to have it.
Please see attached pictures to help.
Regards, Rob
