Re: Follow up: Re: Tech: G08

Mark Jenison wrote:

> Hi all,
>
> I replaced the TIP29B and that fixed it. Thanks Rodger!
>
> Does anyone understand how the spot killer circuitry works on the G08 monitor?
> The Star Trek manual mentions it, yet I can't find the devices on the
> schematics. Anyone?

Only thing I see that looks like a spot killer is the yoke return lines
go to pins 1 & 2 of the high voltage power supply and work their
way into pins 1 & 15 of the IC. I assume they just turn off the
high voltage to kill the spot.

> On Jun 3, 2:55pm, Rodger Boots wrote:
> > Subject: 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
> >
> >-- End of excerpt from Rodger Boots
Received on Mon Jun 21 13:45:37 1999