Re: Sega Star Trek problem, need help!

William Boucher wrote:
> I purchased a Sega Star Trek convert-a-cab about 18 months ago (as
> non-working). It's been sitting in my game room since then waiting
> for me to get to it. I knew the monitor was dead so I worked on that
> first starting just last weekend. I just recently completed
> rebuilding the GO8 monitor and it is working great now.
>
> If anyone wants to know, the 4x TO-3 power transistors are new
> MJ21196G. I list these on my site as replacements for the 2N6259 here...
> http://www.biltronix.com/arcade_electcomp_01.html#transistor_subs_2n6259
>
> The monitor also had a shorted Q603, that's a MPSU10. I replaced it
> with a MPSW42G which is a cheap yet superior part in a tall TO-92
> case. It is available at Digikey. With a small press-on heatsink
> (Digikey HS251-ND), it works great. Similarly, the MPSU60 can be
> replaced by the modern MPSW92G (Digikey# MPSW92R something, I'll post
> it on my site later).
>
> Before I started with the monitor, the game was playing blind with
> sound. After I put the monitor back in, it looked great and was
> playing great. About 10 minutes into it, there was a pop sound and
> the game reset. There is no longer any audio at all and the graphics
> are a bit mixed up and the image appears to be rotated 45 degrees
> clockwise.
>
> The power supply output is exactly +5.05V. Resetting the game doesn't
> change anything. I have reseated all socketed chips and verified all
> 24x 2716 chips on the eprom board. I had some spare boards sitting in
> my basement so I swapped them out one at a time. Most of them didn't
> work but I can say at least that the XY-control board is fine. I'm
> also doing this troubleshooting with the speech and sound boards
> pulled out. I read somewhere that the game should run without them.
> Pulling these two boards did not change the behavior of the game at all.
>
> Does anyone have any suggestions? Any help is appreciated.
>
>
> William Boucher
Hi William,

Have you done the absolutely essential ground/common upgrades? Do a
search for "flameproofing Sega XY games" (GO-8 monitors).

The original Sega power supply had a serious problem where the
ground/common pin would bake and lose conductivity between the monitor
and the logic ground reference - leading to exploding driver transistors
on the monitor.

The cure is to replace the original power supply with a modern video
game switching power supply and to make CERTAIN that the common/ground
wires between the monitor, logic board and power supply are well and
truly connected.

If that was not done it could have easily caused your problems.

I wish I had some pictures of the older SEGA XY games we saved by doing
this modification, however they are all in customers houses with nary a
one having any trouble after ten or more years...

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"
---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com