Hi Dave,
Thanks for your input. I will get back to the scope this week, I was
out for the past few days.
Sorry for the late reply, will keep the group posted of any new
developments as I run some more tests involving what you are
suggesting.
Alex
--- In TekScopes@..., Dave Ashby <dashby@q...> wrote:
Hi Alex,
I would guess the transformer itself is okay, because when you run
it with
no secondaries connected to the PCB and just your test load
(rectifier,
capacitor & bulb) the inverter was drawing a low current.
It is when you reconnected the secondaries to the board - "Next I
proceeded
to connect all the secondaries (one by one) to the PC board with
some short
jumper wires. At first I connected all the secondaries, but still
left the service
jumpers open (just the ones for the +/-8.6, 5, 30, and 100V. The
others I had
previously disconnected I left in the circuit, including the CRT
filaments, HV
Multiplier, and deflection circuit feeds)" - that you started
seeing the high
current.
So, even though the service jumpers are open, there might be
something on
the PCB that is loading one or more of the secondaries. So with
the service
jumpers open and the secondaries disconnected, I would check the
resistance
between the pads on the board in every possible combination - e.g.
there might
be a short between a 5V connection and an 8V connection. I'd check
from
each pad to every other pad that the transformer secondaries go to.
The other possibility is that the problem is in the area of the CRT
filaments, HV
Multiplier, or deflection circuit feeds. It might be worthwhile
repeating the test
with each of these disconnected, to see if one of these is causing
most of the
500mA current draw.
Apologies if you've already tried these ideas. I had fixed a PSU
in a 2230 which
is very similar, and although I found quite a few components blown
in the
pre-regulator and primary side of the inverter, I did get it
going. But there were
no faults on the secondary side of the inverter, whereas in your
case, I guess
there is. Hope you fix it in the end!
David Ashby
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