Franc Zabkar wrote in message
...
On Sat, 19 May 2012 13:52:58 +0100, "N_Cook" put
finger to keyboard and composed:

I now see someone else has been here before and ground off IC5

music-electronics-forum.com/t10881/

Did you see the following post in that thread?

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Have you noticed that pins 1 and 4 (Vcc and COM) of IC5 are reversed
on the schematic (if this is IR21531)?
================================================== ==================

I noticed on the one i'm working on. I was hoping it was an error in
the schematic but it is not.

I verifyed continuity to ground at pin 1.

So the IR21531 is not a drop in replacement as far as I can tell. I
have looked at just about every self oscilating half bridge drive they
sell and nothing that has pins 1 and 4 swapped.
================================================== ==================

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

I'll sling a 4007 under the board beefore powering up again. As my 2153
started pumping out some pulses and oscillated , at least in audible range
with low Vcc, then I can assume pins 1 and 4 are not as in that Mark Bass
schematic.
Something else I've noticed on SMPS generally before but not thought about
why. Around the elevated mains voltage area a line of slotted perforations
in the pcb material. This must be more expensive to produce than a hatched
wide line of white ink at the overlay stage. I cannot see ventilation or a
paliative to possible developement of conductive pcb material as being the
reason