Dear all,
I fixed an old Marantz 1072 hifi amplifier that was not working and blowing fuses.
I could work out almost all of the clunky bits someone put in it in an effort to "fix" it. That dude somehow thought it was a good idea to connect the -39V and +39V rails together with a thick jumper cable
The amp is now working, I get amplified audio on both channels and everything is fine, except when starting up the amp.
There is a nasty voltage spike and DC offset on the speaker outputs when switching on the amp. It settles after a couple of seconds, so switching of the outputs, power cycling the amp and then switching on the outputs after some time does not get the speakers killed
However, I want to get rid of that issue.
Attached is part of the schematic and a scope capture of what I get on the speaker output.
Edit: Nothing connected to the input of course!
Also, here is a link to
a scan of the service manual.
If one of the power caps (C808, C809) was leaking, could this result in the observed behavior or should I be looking some place else?
Thanks and kind regards,
Frederik