Franc Zabkar wrote in message
...
On Thu, 8 Jul 2010 08:24:40 +0100, "N_Cook" put
finger to keyboard and composed:

The cap is 1uF , 280V ac rating. From the .5*C*V*V that comes to 630V, so
something awry there.
No more than 250V m 60% of likely DC rating, and I would have thought
more
like an equal split between 12V and 1800V so about 150V, transformers are
much the same size if that is anything to go by

If the device is designed to output its rated energy over a 9V-12V
supply range, then one would expect that the dump capacitor's voltage
would be regulated. Otherwise the variation in the stored energy would
be (12/9)^2 = 1.8X.

Is there any voltage feedback from the dump cap back to its charge
controller? I'd expect to see a resistive potential divider feeding
one input of an error amp (comparator?), and maybe a 5V or 2.5V
reference on the other input. You may be able to compute the voltage
from the resistance values.

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


There is a chain of 3.3M resistors for feedback , I suspect it would change
the 1.5KHz multivibrator rather than the 300KHz one. There is also the 1 to
2 second repetition cycling, perhaps 3 multivibrator package, also
unreadable marking