In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:

Finally got around to replacing the transformer this afternoon. The
speaker then powered up OK and would play music. Too soon as yet to
know if it will go wrong again or if my 'repair' has caused some other
problem. But so far so good. One nagging worry is that something else
*caused* the transformer to fail, so may do so again in the - perhaps
near - future! Fingers crossed...

Does the transformer sort of look marginal to your experienced eye, Jim?
Or does it vary from the average mains transformer in design - perhaps
to provide the HT? Just seems an unusual thing to fail - and for the
factory to put their finger on the fault instantly.

The mains transformer looks fairly substantial to me. The power required is
quite modest. (e.g. works with a 63mA mains fuse as standard.) and the HV
only takes a tiny trickle in normal use as implied by a couple of 220k
series resistors. So it actually is bigger and bulkier than I'd expected
and to me it looks like it should be fine for the job. The output for HV is
only about 700V rms. The 5kV dc comes from a multiplier stack.

FWIW It is a traditional frame transformer with an external scale size of 6
to 7 cm.

That said there are a few detailed differences in appearance between the
one I removed and the replacement. And there is a '2005.09' code on it that
looks like a manufacturing date. If so, it may have sat somewhere cold and
damp for a time. But no obvious visible sign of any problems.

At some point I may examine it in detail to see if I can detect what is
wrong. I guess it is a shorted set of turns somewhere. But at present I'm
too busy enjoying music to bother. Tried listening to the Honegger Pacific
231 and Pastorale from a recent Prom this morning. Very good. :-))

Slainte,

Jim

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