B250-S amp. in need of attention

[mbic]

I wonder if you could help please?

I have a Revox B250-s amplifier, which audio wise is fine,but it has developed a switch on thump!

The thump is only on the LH channel. The volume controls are incremental keys, and the thump occurs when the volume goes past a certain level and occurs again when the volume is reduced.

If I make sure the speakers are switched out when the amp is switched on, I then increase the volume just below the level where the thump occurs, unfortunately, this volume level is below my normal listening level.

Can anyone recommend a service engineer please? I am in the Birmingham area and I am aware of the two Revox UK service agents.

Mike

[StanleyB]

My first thought is that it is a DC offset problem on one channel.
I have had a look at the service manual at http://www.hifiengine.com/manual_library/revox/b250.shtml and can only see an adjustment for the quiescent current. But a measurement of the DC offset voltage would quickly give an indication if it is an offset voltage problem or not.

[mbic]

There isn't any DC volts present on the speaker terminals.

[Firebottle]

I'm willing to take a look at it Michael if you bring it round. Just north of Dudley so not far from you. :)

[mbic]

Thanks

I have at long last made contact with my usual service engineer, who is going to have a look at it next week.
Thanks again. Perhaps you could email me you contact dtails sometime?