Re: 2N2207 replacement in 547.

Morris Odell

I'm sorry to say those symptoms are classic for the HV transformer thermal
runaway problem. Unfortunately the only cure is a replacement transformer -
you will have seen endless discussion on this subject if you have been
through the archives. I wouldn't advise swapping the transformer from the
other scope, it's likely to have the same problem if it's an original. You
don't want to go through the complex job of replacing the transformer with
another dud. The only source I know of for replacements is Chuck Harris of
this group and I'm sure he will reply to you. I'm traveling in the US at
the moment so have no easy access to the manual to help you with the
transistor replacement. However you are unlikely to do any harm by trying a
BC556. It's not an expensive experiment.

Good luck,


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