Help!! Revox B242 Power Amp - Mono Question?

tedzwedz

Member
2010-09-30 1:40 am
Hi There

Im new to the forum and from York, England! I dont know a huge amount about hifi as you will see from my question which is basic!

I have a Revox B-242 (B242) Power Amp which I have had for many years, and was given for free by a family friend who had a full house Revox multiroom system in the late 1980's. The thing weighs a tonne! (17kg), built to last, and priced accordingly, it was £1800 in 1988 in the UK.

Anyway my question is a basic one - HOW DO I TELL IF ITS PLAYING MY CD's in Mono? is there a simple test, or a track I can play to show left and right speaker playing different tracks etc

Really stupid question I know, because when I press the "MONO/STEREO" switch on the back, on Stereo it only plays one speaker, and on mono plays both! Only one Channel on the LED screen at the front is lighting up

Anyone know why this is? Has one channel stopped working or something, a fuse etc? It sounds nice when playing in Mono mode, with both speakers playing! I wonder if the switch has reversed somehow (dust?)!?

My System is currently Primare D20 cd player, Marantz tuner, 2x Rotel RB-850 Power amps, Rotel Pre

The Revox is the most "High End" in the system, but I need to raise some cash because of redundancy so I think it has to go, and I just dont use it much!

It was serviced by the UK Revox repairs agents Thear Technology in 1998 not long before I stopped using it, with no reported faults.

The Mono mode is called "Bridged Mono", seems to imply both channels are joined together, so maybe both speaker terminals used for BiWiring?

I have tried:-

1) Leaving it in stereo mode and changing the cables left to right only at the amp INPUT connections (leaving other ends of cables connected as-is). The sound still only comes out the same speaker.

I don't know how the amp works, but it would seem even in mono mode both channels, at least with respect to output, need to be functioning to put sound to both speakers?

2) I have tried a different Phono cable too, but no different!

3) I have also tried using the other output from my preamp (it has two, for two power amps)

Any ideas, am I being really thick!?

Kind Regards
Edward
 

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So, with two speakers connected, amp set to stereo, only one speaker works ?
And with amp set to mono, both speakers work ?

Sounds like an input or input switch failure.
Try just one single rca lead into each of the amp inputs.
I suspect you'll only get sound from one input socket, which means the input is faulty.
 

tedzwedz

Member
2010-09-30 1:40 am
Hi there!

Thanks for your message!

I have just tried as you said, and your right, sound only comes through the Black Phono lead socket, not the red one!

Thanks very much, I can now take it to my local store to get them to have alook, at least we know what to start looking at now, thanks!

Kind Regards
Edward
 

tedzwedz

Member
2010-09-30 1:40 am
So, with two speakers connected, amp set to stereo, only one speaker works ?
And with amp set to mono, both speakers work ?

Sounds like an input or input switch failure.
Try just one single rca lead into each of the amp inputs.
I suspect you'll only get sound from one input socket, which means the input is faulty.

Hi there!

Success!

I have had it serviced at my dealer and it is now back at home and working great, it now sings on both channels!!

it was a dry joint on the input board, I have had all the joints redone to stop this happening!

Sadly I have now had to put it up for sale :-( I need the cash sadly, redundancy forces sale, shame after 14 years!

If anyone is interested it is on ebay, item 110609237908

Sorry to sell but needs must!

Its sounding VERY nice, want to get the sale over with before I change my mind!

Kind Regards

Edward