Re: G08 Star Trek with no HV

The saga continues. I replaced Q701-704 today for fun and something
interesting happened when I powered up. It sounded like the high
voltage fired up (didn't get to the front of the machine quick
enough) and then seconds later, a red hot ember dropped from
somewhere near Q703. I immediately pulled the plug to investigate.
It almost looks like paint off of the cap just to the right of Q703
fell off and burned up when it hit the motherboard. I didn't see any
burned components. I got my fire extinguisher ready and powered up
again and everything tests the same as my original post. I can hear
the deflection chatter, but still no voltage on pin 2. Could the
paint chip have shorted something to Q703 that would have fired up
the high voltage?

I used my transistor tester on my meter to check the ones that I
pulled earlier, and they all seem to test ok.

Jeff

On Jan 14, 2007, at 6:52 PM, Jeff Klammer wrote:

> Still no luck with this G08 chassis. How much would you charge me
> to fix it? I'm hoping to have it running by February 3rd for my
> kids birthday party. I think I may have hit my limit on
> troubleshooting this one. I saw a chassis on ebay, but it looked
> overpriced to me. How much should a working chassis go for?
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=016&sspagename=STRK
> %3AMEWA%3AIT&viewitem=&item=260074424452&rd=1&rd=1
>
> Thanks,
> Jeff Klammer in St. Paul (White Bear Lake)
>
> 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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>
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Received on Sat Jan 20 22:07:01 2007