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B-2 goes into protection mode some minute after startup only.

M

MattiasB

New Member
Lately my B-2 will always go into protection mode after a couple of minutes into startup and lasting for a couple of seconds.
Then it goes on without issues for hours.
When entering protection mode there is a horrible static and noise through the speakers.

Calling all the experts, what can this be due to? Can it be serious and needed to be fixed?

I have zero knowledge and experience of intervention in this case and I would have to leave it to a seasoned professional. (Living in Sweden.)

Thanks!
 
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Hello Mattias,
it sounds to me that the DC sensing circuit is doing its job. The source of the problem might vary as this is a 45 years old amp and it long overdue for restoration.
For starters: Have you ruled out the source? Does the amp continues with the same behavior if there is nothing connected to the source?
Same goes for the output: check your connections and test the amp with the speakers wires completely disconnected at first.
 
MattiasB said:
Lately my B-2 will always go into protection mode after a couple of minutes into startup and lasting for a couple of seconds.
Then it goes on without issues for hours.
When entering protection mode there is a horrible static and noise through the speakers.

Calling all the experts, what can this be due to? Can it be serious and needed to be fixed?

I have zero knowledge and experience of intervention in this case and I would have to leave it to a seasoned professional. (Living in Sweden.)

Thanks!
Click to expand...
FB PM sent with info of a Swedish B2 tech
 
Also I should have mentioned that it would be best if you stopped using the amp if the issue is internal.
 
update: switching the direct (DC) to normal removes the issue. So its most probably external. @rottalpha via messages had a good theory for the issue.
My tube preamp probably has an old tube that is juicing DC in a not very nive manner to the B-2 at start. Im seriously considering the local B2 tech with newly designed parts work-over, though.
 
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