(Topic ID: 133727)
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Mary Shelley's Frankenstein
Sega, 1995
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Lisboa
The fact that there is a pattern in the number of missing column (1 ,17,33,49,65...161,177) makes me think this could be an address problem...again don't know where to start. Controller board or DMD.
Columns involved are driven by different chips (hv7708) so I'll discard any problems with dmd chips
Festus, MO
Man i wish i could help, but no ideas. Im watching this thread to learn what it turns out to be though.
This is a common problem if there is a bad connection with the short 14 pin DMD cable. Did you reseat this cable? Do you have another DMD game you can swap cables from?
Thank you Crash!!
I did reseat all cables and also inverted the position of 14 pin cable. I would expect that if the cable was defective at least I would have a different behaviour on my dmd 
I'll try with a different cable as per your suggestion just to make sure!!!
Tks
Thank you Crash!
I though that the idea behind this forum was to help each others and learn how to solve this kind of problems. I guess I was wrong!
Now I see why the majority of questions ends with someone pointing a repair service guy eheheh
Quoted from ze7:I though that the idea behind this forum was to help each others and learn how to solve this kind of problems. I guess I was wrong!
Now I see why the majority of questions ends with someone pointing a repair service guy eheheh
ze7 it is and if this was a normal problem people would chime in and help to get you on your way. Problem is this isnt a very common problem and it will prob have to be traced down on the board level. When we get to that point it is very hard to diagnose over the internet. Someone may still be able to help but this isnt a common problem and i have no experience with it so i cant help.
You started a thread asking for advice, and I gave it to you. Trust me if there was a real way to fix this, I would be happy to help. But the reality is repairing these 192x64 display systems is extremely difficult if not impossible simply due to their design. Can't help you.
Hi there. Due to your diagnosing you can be sure the problem lies with the controller board. Did you try to unseat the processor and re-seat it ? I read once that solved some problems.
Personally I also would do the same with all other IC's that are not soldered to the board and on the ones that are look for bad solder points.
As it reversed suddenly I would think it is in one of the IC's and not any other component.
Does this happen immediately after turning the machine on ??
Looks like a stuck bit. I'd start with the schematics and probe around with a logic probe. You could get lucky and see something stuck high or low.
Thank you guys!!!!
I have already removed the processor and put it back again. Nothing changed...and yes it starts immediately on boot.
I have already chased the data lines in almost every ic and haven't found stuck lines. I'm going to double check just to make sure.
And crash don't get me wrong! I do believe that 99% of any pinball problem as already happened to a bunch of people before. I've been repairing boards for only 3 years and never gave up any repair !!
Logic probe on my other hand while i'm writing!!!
Unfortunately I'm logic analyzer dumb but it seems like that could help. You may be able to pick out the pulse with an oscilloscope, but again that'd probably just be luck.
And I totally agree with having fun with these types of repairs. Nothing ventured, nothing gained(even in failure).
Good luck!
1 week later
1 week later
I decided to pick the logic probe and schematics and start all over again looking for stuck signals. All data and address lines where moving so I went to the output of other ics. Found a stuck high output at U23 a 74LS273 and U29 a 74LS166 both on the same path ... piggybacked a 74LS273 and BINGO!!!!!
Thank you all for your help!!!! Never give up heheheh
Back to repair and a new FUTABA S3003 servo (€8!!!) solved the static frankenstein head!!! Working at 100% now!!!
Unknown
Persistence pays off! Well done.
And I agree that this would be a useless thread if it ended with 'well I shipped it off for repair'. Now that ze7 has posted back with his diagnosis and fix it may help someone else in the future. Good result I say.
Wow that was exciting, it was like watching an episode of Star Trek. Introduce technology problem...enter antagonist to induce conflict...just when all hope is lost the Chief Engineer comes through and saves the day. Epic!
Quoted from Jgaltr56:Wow that was exciting, it was like watching an episode of Star Trek. Introduce technology problem...enter antagonist to induce conflict...just when all hope is lost the Chief Engineer comes through and saves the day. Epic!
Lol...priceless. You are spot on!
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