Andrea

Fortunatly with any problem with the amplifier system we 
have the opportunaty to swap non-functioning and 
funtioning parts.  If you swap the cables going to amps 
1 and 2 at the head amplifier you can see immediatly if 
the problem is in the amplifer or the system control 
unit.
If after swap these leads and the noise you see appears 
on the computer as beam 2 then the problem is in the 
head amplifier.  If the noise still appears as beam 1 
then the problem is most likely in the system control 
unit.

Option 1, the test above shows the problem is in the 
head amplifier, then I would swap the amplifier chip, 
OPA104.  Be aware that these chips are very static 
sensitive and you must take suitable precautions.

Option 2, the test above shows the problem is in the 
system control unit.  Inside this unit there are 3 main 
boards, the middle one is the input board for the 
amplifiers.  On this board there are VFC boards, one for 
each amplifier.  If you are lucky there will be a forth 
board for a TCD input if needed and you can use this in 
place of the one for beam 1.  All these VFC borads are 
identical.

As you heard a 'bang' I would look for any componants 
were blackened or cracked.

Cheers
Peter Stow

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