I looked around for any mentions of buzzing etc. from an AM-8500 (or AM-7040 which is very nearly identical, see attached service manuals) but couldn't find anything. What I could find is people singing its praises (favourably comparing it to amps that sell for a lot more than the Sherwoods these days) and calling it a sleeper.
Read this reminded me, that I noticed some intermittent channel drop out on the left channel when using the "A" speaker terminals when I first got the AM-8500 (I just switched to the "B" terminals and forgot about it):
Most common issue on these are intermittent channel drop out, usually caused by dirty speaker select switches and the switch for scource direct or variable input,
a good deox usually takes care of this issue, knock on wood both mine have performed like a champ for the ro 10 years ive owned them.
https://audiokarma.org/forums/index.php?threads/sherwood-am-7040.632370/#post-8381177
Another thread:
https://www.audiokarma.org/forums/i...ness-strikes-thrice-sherwoods-am-7040.134855/
I picked out a few power amps from well-known brand that the "Stereoplay" put in the same "class" as the AM-8500 & AM-7040 back in the 90ies:
(from their 'eternal' ranking, see attachment)
Denon POA-3000 (1980)
Denon POA-3000Z (1985)
Denon POA-4400A (pair) (1989)
Denon POA-6600 (pair) (1987)
Kenwood L-08 M (pair) (1981)
Kenwood L-1000 M (1990)
Luxman M-02 (1984)
Luxman M-03 (1988)
Marantz MA 500 (pair) (1993)
Marantz SM 11 (1985)
Marantz SM 80 (1991)
Onkyo M-200 (1985)
Onkyo M-5060 R (1983)
Onkyo M-5890 (
aka M-588) (1992)
Pioneer M-73 (1991)
Rotel RB-956 BX (1993)
Rotel RB-970 BX (1994)
Rotel RB-990 BX (1993)
Rotel RHB-05 (1994)
Sony TA-N 55 ES (1990)
Sony TA-N 901 (1984)
Yamaha M-60 (1984)
Yamaha M-65 (1986)
Yamaha MX-1000 (1989)
Yamaha MX-70 (1989)
Most of these sell for a good deal more than the Sherwood these days and they probably all come with their own potential issues,
so I'm thinking I might up my budget for the AM-8500 repair/service if the buzzing can be fixed without breaking the bank.
What other components would make sense to check/replace to improve/restore perfomance or preempt likely future defects?
Also, here's a look at the front board: