Unison Research 845 monos

[bonneville]

Since moving house and in a much smaller room,I have noticed a squeal from one monobloc when starting up from cold this can last up to a minute or so,then it settles down and is as quite as it's partner,which into 99db speakers is pretty good.

I have swapped the valves around ,first the ecc 82's then 83's and then the 845's,and thought I had sorted it only for it to reappear when started from cold.

I was going to sell them and did have a buyer who understandably got cold feet but is still sort of interested if the problem could be fixed.

UKD serviced them last year( £400 plus) and since then they have had moderate use only.I don't mind keeping them as they are the best amps I have ever owned,so my question is can I continue to use them as is or could I be storing up trouble and risk damaging my speakers.

Also any repairers near to Merseyside that could take a shuffty?

Vinnie

 

[SMEagol]

I'd reapproach UKD after such a thorough service judging by the price, and particularly given the light use, should be good for at least another year! That's a lot of dough for it to go the shape of the pear.

 

[lower bullens]

Vinnie, speak to Mike Powell in Bolton he fixed my amp in the summer.

http://www.mpavservice.co.uk

 

[Tel]

Are they valve rectified?

 

[bonneville]

Vinnie, speak to Mike Powell in Bolton he fixed my amp in the summer. http://www.mpavservice.co.uk

Does he do valve work ? He used to be ss only

- - - Updated - - -

Are they valve rectified?

No just uses 1ecc82 1ecc83 and 1 845

 

[bencat]

Hi Vinnie

Mike will look at valve equipment as well he did a service / repair on my Concordant pre . I can recomend Mike as being very good and reasonable in price . Quality of work is first class and he has done work for me from Dac,s to the Krell and as above.

 

[take5]

Vinnie, Mike will look at valve work.

If you need to borrow something whilst these are being fixed, just let me know.

However, Im with Chris. Such a short time after a £400 service, I would be looking for some back up work from the folks who serviced them.

 

[bonneville]

Vinnie, Mike will look at valve work.If you need to borrow something whilst these are being fixed, just let me know.

However, Im with Chris. Such a short time after a £400 service, I would be looking for some back up work from the folks who serviced them.

thanks for offer Brian!I do have other amps to use.

 

[greengoblin]

thanks for offer Brian!I do have other amps to use.

Proper wammer! We always have "spare" amps for occasion like this

 

[Tel]

This squealing noise from cold start might be an indication of a problem with the slow start circuit if it has one. Often you can hear a relay click in after about 30 secs but I am not familiar with this amp. Basically the valve heater circuits are switched on and after the delay the audio circuits get switched in. If this isn't working then it could cause the problem you are describing and would also explain why the problem goes away when the valves get up to working temp.

A minute does seem like a long time though.

 

[bonneville]

it seems to be a two stage warm up there is a second surge after about 20secs it is then when the squeal starts.When the amps are warmed up they are very quite and do sound very good