hey, my brother has one of these monster amp/reciever's, and it's got
2 blown fuses ( 10A, 250v ) inside

he got it cheap because it doesn't work....any ideas what could be
wrong with it?

also does anyone know anything about these? it seems pretty well
built!!

thx

wrote:

hey, my brother has one of these monster amp/reciever's, and it's got
2 blown fuses ( 10A, 250v ) inside

he got it cheap because it doesn't work....any ideas what could be
wrong with it?

I dunno, change the fuses and see if they blow.

Which fuses are they? Are they the protection fuses for the output stages?

also does anyone know anything about these? it seems pretty well
built!!

They are a pain in the neck to work on, but they aren't bad. But in general,
problems so bad that they take out the protection fuses aren't too hard to
locate.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 1 Dec 2003 11:26:38 -0500, (Scott Dorsey) wrote:

wrote:

hey, my brother has one of these monster amp/reciever's, and it's got
2 blown fuses ( 10A, 250v ) inside

he got it cheap because it doesn't work....any ideas what could be
wrong with it?

I dunno, change the fuses and see if they blow.

Which fuses are they? Are they the protection fuses for the output stages?

also does anyone know anything about these? it seems pretty well
built!!

They are a pain in the neck to work on, but they aren't bad. But in general,
problems so bad that they take out the protection fuses aren't too hard to
locate.
--scott


thx for the reply!!

...fwiw. replaced the fuses, and power-on resulted in 2 big 200k (
PW10 200 ohm K, 73FU ) resistors smoking heavily, so we shut it off
again. I wonder what would cause these to fail like that?

I'd guess it's on the power supply board. they are parallel hooked
into a relay nearby on the board.

I wish I could get a schematic for this thing.

funny thing is, when the fuses are blown, all the lights etc function
on the front panel. but when we replace the fuses, they DON'T
function.

In article writes:

...fwiw. replaced the fuses, and power-on resulted in 2 big 200k (
PW10 200 ohm K, 73FU ) resistors smoking heavily, so we shut it off
again. I wonder what would cause these to fail like that?

Too much current being allowed to flow through them through the new
fuse.

I'd guess it's on the power supply board. they are parallel hooked
into a relay nearby on the board.

I wish I could get a schematic for this thing.

Most power supplies are straightforward enough so that you can trace
out the wiring, even if it's on a circuit board, and make your own
schematic. It's great training. Give it a try.

funny thing is, when the fuses are blown, all the lights etc function
on the front panel. but when we replace the fuses, they DON'T
function.

Perhaps because when whatever the fuses are fusing is drawing current,
it breaks whatever's lighting the lights.




--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

wrote:

thx for the reply!!

...fwiw. replaced the fuses, and power-on resulted in 2 big 200k (
PW10 200 ohm K, 73FU ) resistors smoking heavily, so we shut it off
again. I wonder what would cause these to fail like that?

Did you use the right value fuses? They should pop long before those
resistors overheat if it's a well-designed amp.

Those resistors are the emitter resistors for the finals. This sort of
thing would make me suspect your output transistors are bad, but that is
easy enough to check. If all three terminals are tied together, it's time
to replace them.

I'd guess it's on the power supply board. they are parallel hooked
into a relay nearby on the board.

I wish I could get a schematic for this thing.

Why can't you? These are easy enough to fix without a schematic, but
Rotel should still have them. There won't be a Sam's for it. The output
stage is pretty generic.

funny thing is, when the fuses are blown, all the lights etc function
on the front panel. but when we replace the fuses, they DON'T
function.

Right, because the output stage is a dead short, and it's pulling down
the power supply completely. Those fuses protect the output stage.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I had thought of that, but the fuses are the same value as indicated
on the circuit board.

how does one test the output transistors to see if they're good/bad?


thx agan for the help:


On 2 Dec 2003 10:33:19 -0500, (Scott Dorsey) wrote:

wrote:

thx for the reply!!

...fwiw. replaced the fuses, and power-on resulted in 2 big 200k (
PW10 200 ohm K, 73FU ) resistors smoking heavily, so we shut it off
again. I wonder what would cause these to fail like that?

Did you use the right value fuses? They should pop long before those
resistors overheat if it's a well-designed amp.

Those resistors are the emitter resistors for the finals. This sort of
thing would make me suspect your output transistors are bad, but that is
easy enough to check. If all three terminals are tied together, it's time
to replace them.

I'd guess it's on the power supply board. they are parallel hooked
into a relay nearby on the board.

I wish I could get a schematic for this thing.

Why can't you? These are easy enough to fix without a schematic, but
Rotel should still have them. There won't be a Sam's for it. The output
stage is pretty generic.

funny thing is, when the fuses are blown, all the lights etc function
on the front panel. but when we replace the fuses, they DON'T
function.

Right, because the output stage is a dead short, and it's pulling down
the power supply completely. Those fuses protect the output stage.
--scott

wrote:

how does one test the output transistors to see if they're good/bad?

Well, the first thing you can do is just use a continuity tester. If all
three pins read a dead short (less than ten ohms) between one another
in-circuit, it's definitely a goner.

Most other testing will require a meter with a diode test function at minimum.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."