Re: Star Trek pic waving?

William Boucher wrote:
> Just wondering if any Sega Star Trek experts out there might know what
> is causing my GO8-003 monitor to show a very slow kind of a jittery
> wave. The wave travels from right to left and also bottom to
> top about once per 5 seconds. The vectors are all correct and are
> nice and bright. The wave is not an absence of lines but is a shaking
> of them. The shaking tends to be only within about a 1 inch wide
> swath at a time. Vectors in other areas are rock steady. For
> example, when the 3D area is showing a green station, the lines
> separate from each other by about 1/8" as the wave passes by. The
> game is totally playable and the sounds are good.
>
> I just recently rebuilt the entire monitor, all new caps, diodes,
> transistors, many resistors, and all new headers and sockets and
> trifurcon wire terminals.
> My parts list for the monitor is available here:
> http://www.biltronix.com/arcade_electcomp_01.html#GO8_parts
>
> I have just today generated a Digikey order of components so that I
> can renovate the power supply. At present, it is not yet restored but
> all the outputs are bang on. I haven't checked the outputs for ripple
> yet (say due to bad caps).
>
> Anyways, just wondering if anyone has seen this problem before and
> knows the root cause and would care to share their experience.
>
> Thanks in advance...
>
> William Boucher
Have you upgraded the ground connections from the power supply to the
logic boards and monitor? I assume you are using the original power
supply and not a switching power supply.

You will need to fix this or you run the risk of damaging the monitor if
the ground reference shifts enough to bias the drive transistors enough
to blow them.

See page 36 of the Electrohome GO-8 FAQ covers the ground upgrades and
reasons:
http://arcarc.xmission.com/PDF_Monitors/FAQ%20Electrohome%20G08%20Version%200.8%20dated%2025%20Feb%2020.pdf

And power supply upgrades from the Sega XY FAQ @
http://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=segaxyfaq1.6.txt

/===========
Power supply
============

Sega/Gremlin power supplies are not the most reliable. If you have a
dead one,
you have a few choices: you can repair it, or replace it.

In most cases repairing these power supplies is straight forward. If
you open
it up, you'll see there's really not much to it. The voltage regulators are
all mounted and can be easily replaced.

If you decide to modernize your game and put in a switching power
supply, there
are a few things to consider:

1) The Sega/Gremlin power supply has a built in audio amplifier. You'll
need
   to provide your own if you replace it. I've had good luck with using the
   Bally Midway Dual audio amps as a replacement, but any audio amp
should do.
2) You'll need a 3VAC supply for the power-on reset. I've heard that using
   +5VDC as a substitution may work, but your milliage may vary.
3) You'll need +5VDC, -5VDC, +12VDC, and -12VDC. John Robertson says you
   may be able to get by with substituting -5VDC for the -12VDC for the
video,
   but you'll need to adjust your picture.

Or if you wish, you can use a switching power to supply the more common
voltages and keep the old power supply in there and use it for the
things that
may still work (audio amp, 3VAC, -12VDC). Just make sure if you do this to
make the grounds common between the two power supplies./

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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