Sherwood RD-8108R Audio Amplifier

[dick_barton]

I have the above unit that switches on and after a few seconds at most goes into standby mode. Whilst on (that is before going back into standby) the display is functioning.

Has anyone the service manual for this model or perhaps could point me in the right direction.
Thanks

[Andrew F. Ali]

Re: Sherwood RD-8108R Audio Amplifier

Check PSU Trans, Diodes, etc......Then look at the Power Amp Output Semiconductors...any suspicious e-caps or scorched resistors??

[dick_barton]

Re: Sherwood RD-8108R Audio Amplifier

Thanks for your reply. Found a -15V three terminal 7915 regulator with -27V input and no output.
Removed it and tested it on a power supply and it worked OK giving -15V output but I had no load connected.
Put it back in and still had -27V input and 0V output.
Added -15V from external power supply and the amplifier is up and running.
Will replace the 7915 regulator
Thanks

[petehall347]

Re: Sherwood RD-8108R Audio Amplifier

check the ground connection for the regulator

[dick_barton]

Re: Sherwood RD-8108R Audio Amplifier

Thanks for your reply.
I now have the amplifier up and running but if anyone has the schematic for it I would very much appreciate it.
Regards

[petehall347]

Re: Sherwood RD-8108R Audio Amplifier

http://www.givefile.net/smanuals/_av.../rd-8108r.html

[dick_barton]

Re: Sherwood RD-8108R Audio Amplifier

Thanks for the link but it seems to want to download unwanted files.

[dick_barton]

Re: Sherwood RD-8108R Audio Amplifier

As I said earlier it is now up and running after changing the -15V regulator.
Have run it over the last few days, however on two occasions it has emitted an extremely load pop from the speakers and gone into standby.
Leaving it for a few minutes and then coming out of standby the amp will work again as though nothing un-towards had happened.