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Default Transformer shot! (was scope SMPS/ capacitor venting)

On Sun, 21 Feb 2016 13:36:49 -0000 (UTC), Cursitor Doom
wrote:

snip
In one of your pictures there are a couple of diodes that look messed up
(V1809 and V1811) near the bridge. They are supposed to be BY208-1000
(1000v rectifiers), I can see "40" on one, maybe 1N4007?


I like your thinking! But no, the one nearest the bridge is a BY208-1000
alright, the other one to the side of it is a BY134. They both tested
fine out of circuit.


The BY134 is a lower frequency part with 2uS recovery time and is
probably unsuited to replacement of BY208-1000 in any of the snubber
or conversion positions indicated on the schematic primary. It should
be soft recovery, medium speed (200-600nS) avalanche-rated part with a
minimum 800Vprv.

I'd avoid the use of anything advertised as 'ultrafast' (ie UF4007),
as this circuit may need a modest recovery time in order to reduce
power loss and EMI, but they could be used temporarily in
troubleshooting.

RL
 
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