Only one channel on my amp

gazzaaa · Post by **gazzaaa** » Wed Aug 09, 2006 4:07 am

Hi... nothing to do with remotes this one, but maybe you can help

Just got my hands on a nice and cheap. lovely-sounding ROTEL amp but only right channel output works.

Have tried changing over input plugs to different input sources, with always same result, same with Source/tape. Every combination gives me right speaker output only

Have tried Remote speakers, same deal

Have tried cranking volume knob up and down vigorously to see if it was just a little gummed up, no joy

Have tried connecting speakers while amp switched on (yep, I'm an amateur!) and some crackle as I connect them, no sound though.

Have tried swapping over left and right leads from input, and changing input source and cable, but always the same

Any ideas would be very gratefully received. Help!

Cheers!
Gary

underquark · Post by **underquark** » Wed Aug 09, 2006 4:51 am

Sounds as though either the balance is set all the way to the left (elemental error but you didn't say if you'd checked this), the balance connections are loose/broken (internally in the potentiometer or externally where wire should be soldered to it) or the right output jack has a faulty connection. Nice and cheap you say?

gazzaaa · Post by **gazzaaa** » Wed Aug 09, 2006 5:25 am

30 quid (the RA-820BX3 cost around 300 new in 1989 I heard) and is serving me well as a mono amp for the moment!!!

There are separate L and R wheels on the volume knob, no balance control. Yep checked it.

When I turn up volume on left channel the "silence" gets louder. This plus the fact the left speaker outputs crackled on connection made me think the fault is on the way from the input... but where???!?

Cheers for the speedy reply!
Gary

zaphod7501 · Post by **zaphod7501** » Wed Aug 09, 2006 6:35 am

Another nuisance problem would be that the amp is in some sort of "bridge" mode which would turn it into a more powerfull single channel amp. You'd need to research setup modes or carefully read the owner's manual. I don't have any info on this amp. (most of the real Hi-Fi only companies won't deal with the independent service industry or the conventional parts distribution systems)

Try it with headphones (if it has a jack). If headphones sound OK, then the preamp and switching circuits are working, leaving the possibilities in the audio output stage or even a bad (or unsoldered) speaker relay. A novice might be able to resolder a relay: a tech might be able to fix an output stage problem: the Factory would probably need to fix a switching, logic, or decoder problem.

gazzaaa · Post by **gazzaaa** » Mon Aug 14, 2006 3:55 am

Underquark/Zaphod (Mr Beeblebrox, I presume)

The headphones are the same: right channel output only. Took off the cover and to my (untrained) eye there don't seem to be any loose connections... but where would I stard gently prodding?

As for the other possibility of bridge mode: I'll see if I can get info. Thanks a lot for your help

Gary

zaphod7501 · Post by **zaphod7501** » Mon Aug 14, 2006 6:32 am

Another thought would be one (of two) pre-out to pre-in jumpers missing (look at the back and some amps have a mechanical switch for that function)

Internal prodding: I'd look at relays (rectangular plastic boxes).

gazzaaa · Post by **gazzaaa** » Mon Aug 14, 2006 10:19 am

Zaphod,

There are no pre-in to pre-out terminals on this machine, and no external switch either.

Relays all took a prod, but the Rotel didn't speak to me. Internal jumpers took a bit of gentle tickling too but alas I have a mono amplifier here. I've ordered a copy of the manual, but I don't think it's gonna be a great help here. The Rotel has a very basic external interface, and in no time at all you've tried every combination...

Cheers
Gary

Post by **The Robman** » Mon Aug 14, 2006 10:35 am

Do you have any repair shops where you could take the amp to have a professional look at it? If it's something simple it might not cost that much to fix.