Re: Tech: G08

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.

I assume this +9.1 v you refer to is DC.

> 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.

The voltage (when running) at the +9.1 v testpoint seems to be more around 3 or
4 V.

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

I have not tried this. Is it safe to test the deflection board with the HV
unit unplugged? I know you can do this with a WG6100, but was unsure about the
G08s.

Also, is it safe to run the deflection board without it being hooked up to the
deflection transistors?

> 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.

Thanks much for this information, Rodger!

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Mark Jenison E-mail address: jenison@cig.mot.com
Cellular Infrastructure Group Motorola--Arlington Heights, IL
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Received on Thu Jun 3 16:17:38 1999