Re: G08 Star Trek with no HV

Sorry for the slow response. I was trying to get my scope working,
but that seems to be dead too.

As for the G08, I do get 100VDC out of R307. I removed Q900 and
tested with a meter and it appears to be ok. Is there any way to
test further without a scope?

I also re-checked for cold solder joints, etc... when I had it back
on the bench but found nothing. I tested Q901, Q902, and Q903 on the
bench (without removing) and they don't appear to be shorted.

Any other ideas before I throw in the towel?

Thanks,
Jeff Klammer

On Dec 29, 2006, at 6:15 PM, Hans O wrote:

> Yes, no voltage indicates trouble in the X deflection. If you hear
> deflection chatter, you should have enough signal to display
> something on the monitor. Usually the HV unit will still fire up
> with one side of the deflection collapsed.
>
> Some things to check:
> Cold solder joints, especially on the connector, HV transformer
> pins, and T900. Reflow them even if they look good.
> Check for approx. 100v coming out of the little HV board. Measure
> the end of R307 nearest the screw hole.
> Check Q900 (would it still be called the HOT?)
> If so far, so good, then you need to start probing the oscillator
> circuit. May be hard to do without a scope. Start with Pin 9 on the
> IC. If there is no signal at pin 9, then the IC is probably bad.
> Before you chuck it, fix the X section and retest.
>
> If you have oscillation at pin 9, follow the signal through Q901,
> Q902 (on the back of the board), and Q903. Next stop is the end of
> R327 nearest the coil. Last stop is the Collector of Q900 (yellow
> wire, I think).
>
> If you have oscillation up to the HV transformer, 100v feeding it,
> and no cold solder joints, then the last suspect is a bad HV
> transformer (highly unlikely).
>
> Hope this helps.
> Hans O in Chicago
> (If you get totally stumped, I can probably look at it for you.
>
>
> Jeff Klammer wrote:
>> Greetings. I just acquired a Star Trek with no picture on the G08
>> monitor. You can play the game blind and with the back cover off,
>> you can hear vector chatter. The high voltage doesn't seem to be
>> coming on. Here's the voltage readings on the 10 pin to the HV board.
>> 1. Approx +2.4VDC
>> 2. No voltage
>> 3. -9VDC
>> 4. +9VDC
>> 5. GND
>> 6. GND
>> 7. No Voltage
>> 8. 118VDC
>> 9. 10. No Voltage
>> I've done some initial troubleshooting on the G08 chassis
>> (installed Bob Roberts kit), but I don't find any bad parts yet.
>> Can I assume that no voltage on pin 2 means that the problem is in
>> the X part of the deflection board? This is my first time
>> troubleshooting a vector monitor. I'm hoping to find someone in MN
>> with a good Star Trek or G08 vector game so I can narrow down the
>> problem to the Star Trek hardware or the G08.
>> I have read all of the archives and found one similar problem from
>> Dec. 27 of 2005, but it looks like that problem was never solved
>> (or at least never posted a solution). I've posted this on
>> vaps.org also, but so far have not found the solution. I should
>> have my scope up and running in a week or so which may also help
>> troubleshoot.
>> Thanks,
>> Jeff Klammer
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Received on Sun Jan 7 19:04:11 2007