Re: WG 6199 HV section help

Pat Danis wrote:
> Like Ian, I have the same issue with my HV cage. P316 model. R903
> gets fried and I keep frying q901 and q902. I have been thru the
> entire cage and can't find anything bad. Read the FAQ and checked or
> replaced everything suggested. I'm not a smart enough guy to figure
> out what is drawing so much current.
>
> I can only power up the monitor for a few seconds. (about 5-10) When
> I power up the monitor, it is very dim and then I get a high voltage
> crackle and R903 starts to smoke, then the transistors let go. The
> issue I was having before was the image was blooming. I replaced
> ZD902 and I think that stopped the blooming. Now I need to know why I
> keep frying these parts.
>
> Can anyone offer some suggestions? I've been thru this cage so many
> times, I'm starting to forget what circumstance leads to what condition.
>
> Pat

Do you have a ring tester for the flyback? One shorted winding can take
out the parts you are speaking about...

A cheap and easy alternate tester is to use an multi-function audio
signal generator (all of us have these, right? - eBay, "audio signal
generator" look for Sine/Square wave within those) - hook up the output
to the transformer and fire up the generator (square-wave) around 15KHz
@ 10 to 20V. You should see on your 'scope (you have these too, eh?) a
nice signal with a ring that rolls down after about five to more cycles
after each pulse.

There is no reason you have to run the HV cage at the rated DC input,
use a variable power supply and dial it up slowly while you watch the
screen/focus outputs (not the HV lead!) on your 'scope. You may see
something interesting...

John :-#)#
PS, I sell the ring testers as a kit, cheap @ $49.95, I'll knock $5 off
the shipping if you mention you post on Vectorlist.

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
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