Re: More fun with Star Trek

If the fuses blow right away (doesn't take 10 seconds or some delay like
that), then I'd say that most likely you have a shorted deflection transistor.
You could also have a blown MPSU transistor on the deflection board itself.

Hopefully, your custom chip on the deflection board has not bit the big one.
If it has, your left finding another deflection board to get a chip off of.

Reasons for blowing power transistors....

1. improper part... doesn't handle the load
2. voltage going into monitor is overspec.... (Sega spec'd the main power
   supply for 110V, however most people have closer to 120V... this means
   that in many cases the supply voltage to the monitor is slightly high...
   higher voltage especially if you get a spike results in higher loads
   on the transistors) (There is an unofficial way to setup the main power
   supply that will "fix" this overvoltage condition, but it is not 1000%
   proper in that the windings it will use on the main transformer are likely
   not all of the same wiring guage and in theory that could lead to main
   transformer failure over time... although I haven't had a problem for the
   time I was running it this way)
3. Problems in the main game board logic are throwing bad signals to the
   monitor overloading the transistors and causing the fuses to blow. If
   the fuses take a short time to blow then this could be it... or it could
   have been what happened which caused a transistor in the monitor to short.
   (when the monitor went out, did the picture prior to failure look correct?)
   
There is a G08 repair/upgrade/etc guide out there.... I don't have the URL
handy (I'm sure someone else on this list does). If explains the different
transistors, etc).

These are not the most fun monitors to work on... they layout and factory
repairs are quite "hack". However, they can be fixed (I have done so...
unfortunately for me my custom deflection chip was *poof*).

-- Curt

>Date: Mon, 14 Apr 2003 09:02:17 -0400 (EDT)
>From: njs@lucent.com
>To: vectorlist@synthcom.com
>Subject: VECTOR: More fun with Star Trek
>
>
>OK, now our Sega Star Trek has a slightly larger problem. Over the weekend
>we had some friends over and in the middle of everything the monitor went
>down. The symptom is that it blew the two 5 amp fuses on the monitor board.
>I replaced them and watched it blow out the new pair. What part needs to
>be replaced? Is it as simple as a cap job or is there a transistor that
>has failed? Thanks again.
>
>Nick Sauer
>
>
>
>---------------------------------------------------------------------------
>** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
>** message body to vectorlist-request@synthcom.com. Please direct other
>** questions, comments, or problems to vectorlist-owner@synthcom.com.

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to vectorlist-owner@synthcom.com.
Received on Mon Apr 14 07:37:55 2003