My Rotel RB-1050 stopped working. Normally, a second after I push the
button I hear a click when the amp's power stage switches on. Today,
the red light comes on but no click and no output. 4x15Amp fuses inside
are OK.

I bought it used and it worked then, then it sat unused for 6 months
and now it doesn't work.

I thought this amp was bullet-proof...What do you think the problem is?

Thanks for your comments, - d

broken amp wrote:

My Rotel RB-1050 stopped working. Normally, a second after I push the
button I hear a click when the amp's power stage switches on. Today,
the red light comes on but no click and no output. 4x15Amp fuses inside
are OK.

I bought it used and it worked then, then it sat unused for 6 months
and now it doesn't work.

I thought this amp was bullet-proof...What do you think the problem is?

Thanks for your comments, - d

the relay connects the speakers, not the power to the output stage.
Look at the circuit operating the relay, it'll be faulty.

nb if you dont have troubleshooting skills, most amps operate ok if you
bypass the relay, it just means you get a slight clunk from the
speakers on powerup. Thats why the relays there.


NT

wrote:
broken amp wrote:


My Rotel RB-1050 stopped working. Normally, a second after I push the
button I hear a click when the amp's power stage switches on. Today,
the red light comes on but no click and no output. 4x15Amp fuses inside
are OK.

I bought it used and it worked then, then it sat unused for 6 months
and now it doesn't work.

I thought this amp was bullet-proof...What do you think the problem is?

Thanks for your comments, - d


the relay connects the speakers, not the power to the output stage.
Look at the circuit operating the relay, it'll be faulty.

nb if you dont have troubleshooting skills, most amps operate ok if you
bypass the relay, it just means you get a slight clunk from the
speakers on powerup. Thats why the relays there.


NT


Actually in most (all?) amps the relay is part of the protection circuit.
If the protection circuit detects DC voltage to the speaker outputs of
the amplifier stage the relay will not connect the speakers.
This protects the speakers from damage.
Although the fuses are still good there may be one or more failed
components in the amplifier and if you bypass the relay without checking
first, you could blow your speakers.
Sometimes the protection circuit itself fails, but if you're going to
bypass the relay to test this theory, you had better have some really
inexpensive speakers connected that you won't mind possibly destroying.

Jumpster Jiver wrote:
wrote:
broken amp wrote:


My Rotel RB-1050 stopped working. Normally, a second after I push the
button I hear a click when the amp's power stage switches on. Today,
the red light comes on but no click and no output. 4x15Amp fuses inside
are OK.

I bought it used and it worked then, then it sat unused for 6 months
and now it doesn't work.

I thought this amp was bullet-proof...What do you think the problem is?

Thanks for your comments, - d


the relay connects the speakers, not the power to the output stage.
Look at the circuit operating the relay, it'll be faulty.

nb if you dont have troubleshooting skills, most amps operate ok if you
bypass the relay, it just means you get a slight clunk from the
speakers on powerup. Thats why the relays there.


NT


Actually in most (all?) amps the relay is part of the protection circuit.
If the protection circuit detects DC voltage to the speaker outputs of
the amplifier stage the relay will not connect the speakers.
This protects the speakers from damage.
Although the fuses are still good there may be one or more failed
components in the amplifier and if you bypass the relay without checking
first, you could blow your speakers.
Sometimes the protection circuit itself fails, but if you're going to
bypass the relay to test this theory, you had better have some really
inexpensive speakers connected that you won't mind possibly destroying.


You can often check for DC offset (the common speaker killer) with no
speakers attached. Anything more than half a volt is suspect.
Otherwise, a pair of 8 ohm large (as large as you can afford) wattage
resistors is the ticket.

I picked up a couple of 100 watters surplus some 20 years ago, for $5
apiece. They've been part of my bench ever since. Mounted on a large
chassis, I've stressed them up to 200 watts for brief periods--just long
enough to make measurements--with no damage. They 'do' get hot, though.

jak

Jumpster Jiver wrote:
wrote:
broken amp wrote:

My Rotel RB-1050 stopped working. Normally, a second after I push the
button I hear a click when the amp's power stage switches on. Today,
the red light comes on but no click and no output. 4x15Amp fuses inside
are OK.

I bought it used and it worked then, then it sat unused for 6 months
and now it doesn't work.

I thought this amp was bullet-proof...What do you think the problem is?

Thanks for your comments, - d

the relay connects the speakers, not the power to the output stage.
Look at the circuit operating the relay, it'll be faulty.

nb if you dont have troubleshooting skills, most amps operate ok if you
bypass the relay, it just means you get a slight clunk from the
speakers on powerup. Thats why the relays there.

Actually in most (all?) amps the relay is part of the protection circuit.
If the protection circuit detects DC voltage to the speaker outputs of
the amplifier stage the relay will not connect the speakers.
This protects the speakers from damage.
Although the fuses are still good there may be one or more failed
components in the amplifier and if you bypass the relay without checking
first, you could blow your speakers.
Sometimes the protection circuit itself fails, but if you're going to
bypass the relay to test this theory, you had better have some really
inexpensive speakers connected that you won't mind possibly destroying.

I guess I was wrong to assume V_out would be checked before connecting
up.


NT

Thanks for your comments.

The speakers are DIY and work on another amp. I think I would hear the
output click even with no speakers attached and I don't.

I wonder if it could be the 12V/signal trigger (set to bypass since I
don't have the preamp)

How do I find a circuit diagram for a rotel RB-1050?

Thanks,
Dave



p.s. The last setup with the amp was computer soundcard speaker out to
a 25Kohm stepped attenuator (another DIY) that I just finished, and a
set of crappy speakers that I could blow and not care about. Resistance
values on the attenuator checked out.
RB-1050 input overload is 1V/33kOhm, I think soundcard output is up to
~1V