"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N_Cook" wrote in message
...
I'm being spun the story that this was put into storage and on powering
up
again , just the mixer section was working.
So the following is hypothetical but is it a possible scenario?
Does not say anywhere that this amp can be bridged, but also does not
say
it
can't be bridged so perhaps a green light to the owner to run both
channels
together.
Anyway blown fuses and some shorted TO3 in both channels. One 16 amp
rated
relay had an obvious brown patch inside its casing, opposite the
contacts,
but still worked at test levels when the active was replaced. The good
looking one did not click over but its coil ok and audio output up to
the
one contact . Both replaced as due to overheating, the plastic linkage
from
contact carrier back to flip lever are melted/deformed. The brown
stained
one has a serious pitting , well reverse of a pit, sticking out of a
contact.
Now if due to dirt or initial pitting , then poor contact and then
making
and breaking current under serious load could that in combination with
speaker insductance create spikes of a few hundred volts to knock out
active
in both channels ?
If the bad relay was passing less amps than it should, then excess load
on
the other relay and so both overheat.

If DC passed to the speakers , from blown TO3, due to a short in
speaker
lead say, then I doubt the situation would last long enough to cause
the
relays to overheat from assumed good state previously




If DC passed to the speaker, there is a good chance the contacts arced
when
the coil was shut off, keeping the connection to the speaker rather than
breaking it. They might bring you a dead speaker later.

But more likely due to Numpty error.
Some Numpty did something stupid to one side and blew it up, then they
did
the same stupid thing to the other side.
Like plugging an external power amps outputs into the mixer's power
outputs.

Or possibly one side blew ages ago and they'd been running it mono until
the
other side blew.



Gareth.



Occam's Raison again






Whilst we're on the subject, it is well worth noting what I said about the
speaker relay not always breaking the contact because it arcs. Few of these
relays' normally open contacts are grounded, so you may like to modify the
ones you see that are not, as I know you particularly like this sort of
thing.

Info on this (actually courtesy of Phil Allison) can be found he

http://sound.westhost.com/project33.htm



Cheers,


Gareth.