Rotel RA1312 heavy amp problem

[N Cook]

This large rack amp was last used in a social club, working order, many
years ago.
Not powered up since and only front lamps now come on.
I assumed,initially, it was just lack of amp - preamp interlinks but no.
I'm loathe to explore unnecessarily if its an equally silly error as it is
that nasty brittle age hardened single conductor wiring loom and wire-wraps
everywhere - typical 1960s, probable manu date 1969.
Good stable +/-50V dc rails and cold "diode " checks of all the o/p trannies
look ok but the speaker line relay does not click over.
Any inside gen ?

 

[Steven Dinius_]

Just use RCA cords those interconnects are 99.928467% RCA phono jacks
anyway. Secondly, I doubt it could be as bad as a Sansui 3000A or some of
those tiny sports cars you guys made ;-)...if it is c.1969 as you say it's
not going to be like that 1603? "monster" receiver with plutonium pellets
and handservants needed to feed it. Just a lot of capacitors, I'll bet, and
one of them ought to be bad (especially the big ones over 1000 mf), causing
the protection circuit to abort liftoff. Second place to look is all that
wiring, third maybe any block resistors. What I've gathered from some
1968-71 sets (having an unplugged, unpowered set discharge through my
stereophones was a "thrill" too), so I'm just theorizing, still hope it
helps. Those era sets are so charming but so arcane as I was maybe 2 or 3
and things were much different by the time I got to looking in them at maybe
12.

 

[N Cook]

Just use RCA cords those interconnects are 99.928467% RCA phono jacks
anyway. Secondly, I doubt it could be as bad as a Sansui 3000A or some of
those tiny sports cars you guys made ;-)...if it is c.1969 as you say it's
not going to be like that 1603? "monster" receiver with plutonium pellets
and handservants needed to feed it. Just a lot of capacitors, I'll bet, and
one of them ought to be bad (especially the big ones over 1000 mf), causing
the protection circuit to abort liftoff. Second place to look is all that
wiring, third maybe any block resistors. What I've gathered from some
1968-71 sets (having an unplugged, unpowered set discharge through my
stereophones was a "thrill" too), so I'm just theorizing, still hope it
helps. Those era sets are so charming but so arcane as I was maybe 2 or 3
and things were much different by the time I got to looking in them at maybe
12.

Thought i'd found problem I removed the large cap that seems to be for
timing thinking it was leaky and powered up and the relay clicked over at
power up, but replacing with a good one returned to always off.
The line back from the main amp settles out to 0V soon after power up so
that is probably ok, will try replacing the small tranniess in the relay
ANDing and relay drive next as prob seems to be in the protection circuitry

 

[N Cook]

cured - rail monitoring problem - write up will be on one of the repair
brief files on URL below