Re: Cinematronics/Vectorbeam Monitor repair mini-doc!

Testing the Vector monitors with the yoke unplugged is like running an
audio amp with the speakers unplugged. No load means little if any risk to
the output devices if there is no input.

If you have a scope you can hook it up across the yoke lines to see the
results, if not, use a 15 watt 115VAC light bulb...the bulb will glow
brighter (if no input to the monitor) if one of the output transistors is
shorted. The bulb will not pass much current (whats 15/115V = X/60V? about
7 watts or 100MA - please check my math, but it is pretty low current!) -
need my ohm's wheel to figure that out..

I've used the light bulb test on my servicing of jukebox audio amps over
the years (25) and no damage to output transistors, you can check that the
amp is set up correctly and the lamp gives an instant indication of
problems...with no smoke!

John :-#)#

At 08:40 PM 06/07/2002 -0500, Gregg Woodcock wrote:

>----- Original Message -----
>From: "Mark Jenison" <jenison@enteract.com>
>To: <vectorlist@synthcom.com>
>Sent: Friday, July 05, 2002 6:11 PM
>Subject: Re: VECTOR: Cinematronics/Vectorbeam Monitor repair mini-doc!
>
>
> > >
> > > Now if you are still blowing breakers, remove the connectors for the
> > "HORIZ"
> > > and "VERT" heat-sunk transistors, and retest for no more than 15 seconds
> > or
> > > so.
> >
> > I assume at this step, you have the deflection coil unplugged, because you
> > aren't supposed to test with the deflection transistors unplugged and the
> > coil plugged in. I tried this and my deflection board toasted
>immediately.
>
>Immediately is likely a bit of an exaggeration. Generally speaking, the
>resistors
>will begin to cook before a picture comes onto the screen (i.e. don't bother
>looking for a picture unless you've upgraded to 5W or intend to replace
>them)
>but that still is in the tens of seconds. I suppose the suggestion is a
>good one
>(although I personally have NEVER done so and have also never had a problem
>burning those guys up) except that Vectorbeam's do not have a connectorized
>yoke!
>
> > I would not recommend this step at all in fact; I would simply recommend a
> > mandatory upgrade to the 2N3716 and 2N3792 transistors.
>
>Well.... OK, you're probably right on this one.
>
> > > If one is bad upgrade to 2N3716/2N3792 as found in the Atari model's
> > > vector monitors. These are beefier parts for the same purpose. Don't
>ask
> > > me which substitutes for which; figure it out (that's what I do EVERY
>time
> > > :)!
> >
> > A good way to remember which substitutes for which; take the last number
>of
> > the original transistors and multiply by two: The one that ends with '8'
>is
> > replaced by the 2N3716 ('16'), and the one that ends with '6' is replaced
>by
> > the 2N3792 ('12'...ends with '2' :-)).
>
>Good tip! You don't know what those white things are on the yoke wires,
>do you?
>
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Received on Sat Jul 6 22:08:07 2002