Re: Tech: G08

The +9.1 volts comes through Q401. The +63 goes through
R404 (220 ohms, 10 watts) to the collector of Q401 (TIP29B
with a heat sink added). The +63 goes through R405 (8.2 Kohm,
.5 watt) to the base of Q401 and also through D408 (1N914) to
ZD401 (9.1 volts, .5 watt, 5% zener diode, a 1N5239B) to ground.
This should put 9.1 + .6 volts (9.7 volts) on the base of Q401.
You lose the .6 volts in the emitter-base junction of Q401 which
leaves 9.1 volts at the emitter. C405 (10 uF, 25 volts electrolytic)
filters the +9.1 volt output. C701 (47 uF, 16 volts electrolytic) also
filters this line. And so does C905 (22 uF, 16 volts electrolytic) in
the high-voltage supply.

Look to see if the +9.1 volt supply is shorted to ground. Zero ohms
could be one of those filters. 24 ohms or so could be a shorted
C911 (100 uF, 16 volts electrolytic) in the high-voltage supply.
Around 70 ohms could indicate a shorted Q902 (MPSU07) in the
high-voltage supply.

Does the +9.1 come back with the high-voltage supply unplugged?

There is also a -9.1 volt supply formed by the -63 volts going through
ZD402 (9.1 volts, 1 watt, 5%, no part number given) and filtered by
C406 (10 uF, 25 volts electrolytic), C601 (47 uF, 16 volts electrolytic),
and C904 (22 uF, 16 volts electrolytic) in the high-voltage supply.

Mark Jenison wrote:

> Hi all,
>
> I have two G08 monitors which I'm having trouble debugging.
>
> They both have known good HV units and known good deflection transistors. Both
> of them sound like they are deflecting correctly, but no picture is showing up,
> and no HV is on.
>
> One seems to not be generating the 9.1V (is this AC, or DC?). Anyway, I was
> wondering if anyone knew which part was regulating this voltage. Is it the
> TIP29B, or is it regulated by the HV, or by the custom chip in the deflection
> board.
>
> It amazes me that we have such good documentation on repairs of the WG6100 and
> Cinematronics monitor, but there is no good repair guide for the G08. I tried
> to make one (or at least the template for one), but it needs more technical
> meat from the gurus. See here:
>
> http://www.enteract.com/~jenison/mars/faq/G08.FAQ
>
> If anyone wants to contribute to the document, let me know. Thanks!
>
> ____________ ______ ___ _____ __ ____________
> / __/ / / / |/ / / |/ //|/|/|_______________
> Mark Jenison / __/ /_/ / / / | // | / |__ __/ _ /__ \ Sega/Gremlin
> jenison@ /___/___/_/_//_/_/_/|_//__|/__| / / / // / / Color Vector
> cig.mot.com /_/|_| /_/ /____/_/|_| Arcade Games
> ____________ The One and Only 4-player vector game ____________
> when the monitor is working
Received on Thu Jun 3 15:02:22 1999