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Ah ha! I think I found the right place to send my question!
Question from Matthew: I think I found where I SHOULD have sent my question the first time! Disregard the comment on episode 48’s page as well as the Facebook post since I’m assuming those may not have been the proper places to send my question.
Hey guys, love the podcast! Thanks for all the help you provide to us lowly DIYers! I’m having a hard time bringing my 19″ G07 monitor back to life. What happened is this, when I was attempting to adjust the monitor I made the mistake of crossing my Horizontal Centering Jumper (W422) over to Vertical Centering Down pin and needless to say that was more of a practice in poor judgment than it was much of anything else.
Now I have a poor, lonely Ms. Pac Man machine playing blind. I’ve dug in quite a bit, first checking the obvious, both fuses (F901, F902) are visually fine and test positive for continuity. Upon inspection I noticed resistor R507 was blown, so I replaced it. After that I found the Troubleshooting Flow Chart For Monitors by Randy Fromm. I discovered that my B+ value is too high (150.1). Following the chart I removed the X-ray protector transistor X701, put on my lead cup and powered it on. Still nothing from the screen. No neck glow, no raster. After putting my X-ray protector transistor back in, I went about checking for voltage on my H.O.T. for which I’m reading the same 150.1, potentially ruling out a hairline crack in the board or bad solder joint. I next checked transistor X501 and I believe it tested bad so I replaced it. Still nothing. After that I replaced my H.O.T. just for good measure. In my research I came across a Bally/Midway service bulletin from 1982 regarding servicing a G07 monitor with B+ voltage of 138.5 VDC or more and it confirmed the issue should reside in one of five components
IC501 (Integrated Circuit)
X501 (NPN H/V power transistor)
T-501 (Horizontal Drive Transformer)
X01 (H.O.T.)
T-502 (Flyback)
As I had already replaced two of the parts on that list, I bought a few replacement parts from twistywristarcade.com which included IC501 and Horizontal Width Coil (which too needs replaced. Not sure if it’s not functioning but the hardened gluey substance spread across the coil is broke so it moves around if you bump it.) I am unable to find a replacement Horizontal Drive Transformer on any retail site and I wanted to wait to install the less expensive parts before buying the more expensive flyback. My questions are thus, can this no raster condition be caused by a faulty Horizontal Width Coil? Can a new IC501 be installed new like that or does it need to be programmed prior to? What other ideas might you have that may contribute to my problem? With your infinite wisdom and experience, what would be the next few steps you would take considering what caused the condition and what I’ve already done so far to troubleshoot?
I am confident I can fix this problem myself if it is in fact a problem that can be fixed but I don’t want to keep playing parts-darts if I can help it.
Thanks again for all your help! You’s guys are da best!
Matthew from Spokane, WA
Oh! And if you can, give a shout out to the Spokane Arcade Club group on Facebook. Just got that started so if anyone in the area listens to the podcast please join and support the local community of collectors. I’m quickly finding out I’m not the one only out here.
1 answer
Response from Jonathan: Matthew,
Wow, sounds like you have done a lot of great troubleshooting already. Let’s see if we can figure out your remaining questions…
> Can this no raster condition be caused by a faulty Horiztonal Width Coil?
If you had a bad horizontal width coil, you would usually have something on the screen (like partial or full vertical collapse). Of course, there’s always a chance that it’s malfunctioning in just the right way to cause a blank screen. If you are having a hard time adjusting the horizontal width coil, I would definitely replace it regardless.
> Can a new IC501 be installed new like that or does it need to be programmed prior to?
No programming should be required with IC chips. They should come ready to install. In fact, I wouldn’t be surprised if replacing this fixes your issue.
> What other ideas might you have that may contribute to my problem? With your infinite wisdom and experience, what would be the next few steps you would take considering what caused the condition and what I’ve already done so far to troubleshoot?
I don’t know about “infinite wisdom and experience” but we do what we can. =) Now, replacing IC501 would definitely be our next step so if that works I would ignore the rest of these suggestions. With that said, it’s probably a good idea at this point to check some diodes and solder joints. Even though your fuse F902 is OK, I would still recommend checking diodes D901-D904 just in case. They should be fine but you never know. I would go ahead and refresh the solder around T501 even if you don’t see any cracked/cold solder joints. It could just be that the old solder is not making a good connection there. Unfortunately I don’t think anyone sells a replacement for that transformer so you’ll have to borrow one from another chassis if it is indeed bad. Of course, I would probably replace the flyback before going that route as they are more readily available.
Also, we’ll try to remember to give a shout out to the Spokane Arcade Club on Facebook on the next podcast. Hopefully that will help you find some more people in your area.
Hope that helps. Thank you for your question and good luck with your repair.
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