Re: Flyback Troubleshooting help

Jess Askey wrote:
> Hi Everyone...
>
> My Amplifone raster saga continues, I now have two deflection boards
> and an original deflection coil (thanks John!) but nothing is working
> yet. Im probably going to go into a little too much info here, but I
> figure more is *more*. :-)
>
> First Important Note: Im running this deflection PBC off the Atari
> switching power supply which puts out 145VDC for the monitor. Oddly,
> this is fed directly in where the 125VAC goes, which if you do the
> analysis, is just fine... it is actually a little easier on the
> monitor power regulator (120V) since it only has to regulate down from
> 145VDC rather than 170VDC. The reason this is important is that the
> switcher shuts down in an overloaded condition (saving me fuses and
> more) any time I power up the monitor. When I first was
> troubleshooting this monitor I had a few times where I doubted that
> the deflection PCB was the problem so I put it on the regular 120VAC
> line... well, that proved one important thing twice (yes, I was
> stubborn enough to learn this the hard way twice). I shorted the HOT
> and the power regulator. So, lets just say that Im pretty sure that
> using the Atari switching power supply is working well as a
> troubleshooting method.
...

Let me get this straight - you hooked the monitor chassis DIRECTLY to
the mains - 120VAC?

No ISOLATION transformer?

Small wonder you blew the transistors. You will also have blown diodes
on the input bridge - I hope you checked them too...

You must always use an isolation transformer when checking raster
monitors - I even do so with the ones having the built-in switching
supplies just to keep in the habit...

Now back to troubleshooting the flyback. I'm going to dig out my
schematic and ponder.

John :-#)#

-- 
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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