royalmp2001 wrote:
Hi,
I got hold of a 20yr old dead Adcom hifi power amp recently together
with the service manual.
The fuses on each +ve line have blown, the fuses on the -ve lines were
ok.

I have not tried the amp out - I have taken out these supply line fuses
(between the psu and the main electronics), therefore isolating the
power supply to the two amp boards, and checked the psu with a
voltmeter and oscilloscope.

The psu seems fine.... + and - 49.4V out, and all lines giving out
about 10mV ripple. One rail had 20mV ripple.

As this is quite an old amp, and I understand the electrolytics go
first (after pots, swtiches and connectors), what tests can I do on the
caps to see what kind of life I can get out of them. I can replace
them, but if it is not necessary I don't want to do it.
Thanks, guys.


Electrolytics are probably not your issue, although they do age. It
sounds like you have some sort of short on the B+ line. With the fuses
out of circuit, compare the resistance to ground of load side of the +/-
rails.

My guess is that you're gonna find a shorted output device....

jak