Meat Plow wrote in message
...
On Wed, 7 Jul 2010 14:46:36 +0100, "N_Cook" wrote:

2 stage derivation of (should be) 1800V pulses.
Fence had failure in the first stage probably due to intermittant
corroded
battery supply contact.
Anyway the 15A 60V 8N06 powerFET blew along with an associated double
diode
BAV23.
Replaced both and works to some extent. This FET has plenty of drive 5V
of
pulses of repeat 3uS for the gate and about 3V ringing swing on the
output
to the first step up transformer. I assume that is as to be expected,
never
having the chance to see hot-side SMPS drive scope traces.
But rectified output only climbs to about 1V of DC before the final stage
(unreadable marking) thyristor discharges that supply into the second
step
up transformer, but of course not even enough to get a glow on a 110V
neon.
Doubling the C setting the 3uS pulses, to give longer repeat rate and
that
intermediary voltage rises to about 3V but still not enough for any
proper
final output. Adding more C and DC is then much less than 3V.
What would people expect the intermediary DC to be? obviously higher than
12V battery supply
Next stage would be disconnect the thyristor if that should be working
but
leaky and draining the intermediary DC but any other ideas? Would explain
why the printing is very indistinct I suppose.
DC ohms of the airgap type transformers are
intermediary 0.1R//10.6R
HV 0.3R//29R which seem reasonable, ie not major shorted turns if any


I would expect the output to be at fault when you take into
consideration all the short circuits electric fencing can encounter.

I've disconnected the HV section and no difference. The o/p of the
intermediate is 4V pk-pk pulses with designed 3uS osc i/p. Barely enough to
exceed the bank of 6 seriesed rectifier diodes . Inductances of the
intermediate Tr are 0.1mH and 84mH . i'm wondering if there is shorted
turns, will try and find some SMPS to try in reverse.
The output Tr is E-I iron cored not HF on closer looking