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Old 31st Mar 2021, 9:49 pm   #14
ortek_service
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Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
Posts: 1,398
Default Re: Weir HSS100/4 PSU blowup

Yes diodes (and most semiconductors) tend to fail short-circuit with too much current.

Farnell do have lots of the BZW06-13 diode in stock, although you do have to buy 5off (probably the same as RS) and find some other stuff to buy to avoid handling charges (also same with RS, bnless account holder?):

https://uk.farnell.com/taiwan-semico...-do/dp/2677548

- And they do list a few suggested alternative to this, which RS may actually have in stock (Although not necessarily in the UK..)

It does seem a very odd circuit, and I'm wondering if R16 is a king of start-up resistor and T1 / D11 provide the base-bias supply when it is running. It seem the more ac current there is through TR4 emitter, the more feedback drive it gets, so could be some kind of adaptive efficiency measure.
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