Frozen & fried amplifiers

[None]

I just acquired two QSC RMX850 amplifiers, for pretty close to free.
They have been stored in an unheated and uncooled garage for more than
a year, during which time temperatures have ranged from about -25 °C
to 40 °C (about -12 °F to 105 °F). Two channels out of four are DOA,
which is no surprise. I expect that the thermal extremes have been
hard on any or all solder joints, and one of the back panel DIP
switches is implicated in one dead channel, which should be relatively
straightforward to replace.

Is it worth trying to repair these amps? I have a couple of
well-treated 850's which suit my needs quite well, and I'd be willing
to invest some time and money to get these frozen and cooked models
working if possible.

[Les Cargill[_4_]]

None wrote:
> I just acquired two QSC RMX850 amplifiers, for pretty close to free.
> They have been stored in an unheated and uncooled garage for more than a
> year, during which time temperatures have ranged from about -25 °C to 40
> °C (about -12 °F to 105 °F). Two channels out of four are DOA, which is
> no surprise.

It might have something to do with why they were stored. QSC just do
that - one channel goes out.

> I expect that the thermal extremes have been hard on any or
> all solder joints, and one of the back panel DIP switches is implicated
> in one dead channel, which should be relatively straightforward to replace.
>

The local thermal extremes well exceeded 105F while they were running,
at least in places. And I don't figure -40 would hurt an amp unless
somethig thermally contracted enough to break.

I ran a $50, card-deck sized Linux machine in a chamber once at -20 for
.... two weeks. Never missed more than one ping in a row.

> Is it worth trying to repair these amps?

Beats me. Watts are a dime a dozen these days.

> I have a couple of well-treated
> 850's which suit my needs quite well, and I'd be willing to invest some
> time and money to get these frozen and cooked models working if possible.
>
>
>

--
Les Cargill

[Bill[_20_]]

In message >, Les Cargill
> writes
>And I don't figure -40 would hurt an amp unless somethig thermally
>contracted enough to break.
>
>I ran a $50, card-deck sized Linux machine in a chamber once at -20
>for ... two weeks. Never missed more than one ping in a row.

When we built the boat I soldered a lot of small copper tubes to a
copper sheet and clamped it, folded over and with the tubes hanging
from, the bottom of the ice-box of an old fridge whose door had been
removed.

A gaffer-taped polythene sheet directed the drips into the salad box at
the bottom of the fridge, which we emptied every day or two.

This dehumidified the garage we worked in for about 3 of the 5 years.

It failed when the tubes started to fall off. The solder had taken on a
sort of crystallised look and just gave up.
--
Bill

[Scott Dorsey]

None > wrote:
>I just acquired two QSC RMX850 amplifiers, for pretty close to free.
>They have been stored in an unheated and uncooled garage for more than
>a year, during which time temperatures have ranged from about -25 °C
>to 40 °C (about -12 °F to 105 °F). Two channels out of four are DOA,
>which is no surprise. I expect that the thermal extremes have been
>hard on any or all solder joints, and one of the back panel DIP
>switches is implicated in one dead channel, which should be relatively
>straightforward to replace.

Squirt a little DeOxit in the dip switch and it might be just fine. What
happens in storage like this is more apt to be corrosion than solder joint
failures (unless it's RoHS stuff in which case all bets are off). That
means switch contacts, internal connector contacts, etc. are all going to
need cleaning.

>Is it worth trying to repair these amps? I have a couple of
>well-treated 850's which suit my needs quite well, and I'd be willing
>to invest some time and money to get these frozen and cooked models
>working if possible.

I think these are actually pretty good-sounding amplifiers that never got
the reputation they deserved, and rugged too. I bet with some cleaning
they'll come up fine. If it takes a little more it is probably worth it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."