"Phil Allison" wrote in message
...
Arfa Daily wrote:



I just loved
the character Arthur Daley for the wicked sense of comic timing and the
malapropism he employed.


** Like: " The world is your lobster... "


Unfortunately, it's not an easy task to get to the secondary side of the
PSU, as it's one of those two-board constructions, where one power amp is
stacked on top of the other, and all of the bridges and filter caps for
both
amps are, needless-to-say, on the bottom board where you can't get to
anything.

* You could snip the leads for the main secondary ( leaving the CT) and
join them again if the tranny proves OK.


Hadn't thought of that. I've got schematics for the thing, so shouldn't be
too hard to identify which wires are what. The primary is on a plug that's
easy to get to, and all is well with that pulled off, so nothing else on the
input board is the problem.




Before going to all of the trouble to get the top board out to see if I
can
unplug the tranny secondaries, I'm waiting on the shop getting in touch
with
the owner to give him an estimate of what it might cost, depending on
what I
find. I'm not sure what the spares position for Crown stuff is like here
in
the UK, if it needed a tranny ...

** Out of curiosity, I stripped down the tranny from that XLS602. Internal
shorts in large toroidals are very rare, especially with no other fault.

The whole thing was rough as guts, with a wound core made from dozens of
off- cuts of steel strip tacked welded together and bits of cloth tape
covering the edges. Normal toroidal cores are precison made and have
moulded plastic covers covering all sharp edges, where the primary is
wound.

That's interesting. If this turns out to be the tranny, and the owner goes
ahead - assuming we can get one, of course - I will try to find the time to
have a look. Over the last couple of years, I've had probably three or four
large toroidals with shorted primaries, so maybe there's some Chinese
factory churning out cheapies like the one you saw, virtually made from
scrap ...


The twin 120/240 primary was bi-filar wound placing 120VAC between every
adjacent turn, a dodgy practice at best and fatal if the enamel coating
ever gets damaged.

Yes, not a good practice for sure. I suppose though that it's hard to find a
way to wind a twin primary on a toroidal core where you're trying to keep
the profile low, and a similar level of core coupling from both windings.
Much easier when you have a traditional E-I core and can have two primaries
stacked on top of one another, I guess

Arfa


... Phil