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Arcade PCB repair - Instant visual diagnosis: Palette RAM/PROM failiure
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- čas přidán 26. 05. 2017
- The colors with this JAMMA arcade board are completely messed up. Any clue to what is going on? This is a case of an instant visual diagnosis which should exemplary help you with your arcade repairs.
another great vid dr. just cought up with the 2 videos ive missed and dont be scared of doing the same games its good for if people get a double dragon and maybe have one of the problems that you describe and repair in one of your many double dragon videos. but again dr keep up the great work
Thank you very much! This board was actually the last of a stack of 4 .:-) Some other games will be coming soon. I have a dead centipede coming in. Maybe a 1942 by Capcom. Maybe a Donkey Kong.
Good video. I agree with most of it except on the (n) possible colours. For Frogger, it uses weighted resistor DACs at 3-bit p/col. Use an scientific calculated and the (xy) function to get the number. Other than that I ♡ your work. 5☆
Great video! I've been doing PCB repair for several years, and this is still very educational. Seeing the Frogger schematics reminded me that I've got one of those on the shelf awaiting repair. It is repeating every few lines of the graphics, as if there's a counter or addressing problem. The schematics I have are not a very clear copy, so it's really hard to read.
Counter or addressing problem - yes very likely. Thank you for watching my vids and your nice compliments!!! I actually watched a couple of your vids as well - the last one I watched was about the Daytona USA games - very educational and helpful insights there!
Thanks! I wish I could upload more stuff. I fix arcade games for a living, so there's always a lot going on at my work. If there's any certain game you'd like to see, let me know. My favorite thing to do is find really messed up games that have been stored for years and bring them back to life. The more screwed up it is, the better :-)
I'm looking forward to your future videos. It always great to find other people doing the same stuff I do, especially nowadays when it's less and less common to see component level repair.
Exactly! It's great to find people which actually enjoy messing with those classic games as much as I do! :-) It is so much fun getting a beat up game or pcb back on its legs. My next vid could be a ghost 'n goblins pcb lets see how it turns out... :-)
I just had another look at what that Frogger was doing. Each line of text is drawn twice, and each sprite shows two top halves instead of a top and bottom. Since Frogger uses a vertical monitor, the problem should be in the horizontal counters I think?
I actually have a Ghosts N' Goblins board on the shelf. Beware the Capcom pinout that looks like JAMMA, but is not :-)
yes horizontal counters. one of the counter signals like in the range of h2, h4 or h8 stuck high or low somewhere would be enough to cause this
Inhave issues with my liquid kids
The game show just green.
Reset the rom .
but the problem was a agde connector
After cleaning the area the color fixed
These videos have been very educational. I just subscribed to your channel and look forward to more great repair videos. I have a similar problem on a Defender board where there is mostly blue tones and no red color. How were you able to isolate this to the color RAM and not the buffer or something up or down stream from the color RAM? I'm using a logic probe and don't have access yet to more advanced tools.
Very good question indeed. You are right, I didn't quite point out so clearly why you should immediately think of a faulty ram in the case of this board. The reason is actually the color glitching and flickering that occurs on the title screen. That is probably caused by the ram being read and returning different "random" values for the same ram location each time it is read.
Generally in the case of a palette issue the problem can only really be the rams or anything down the stream, not really up the stream. For the buffer being faulty it would have had to be a more constant color issue like only blue colors all the time.
I looked at the defender schematics and maybe with your issue as you describe it (no red, mainly blue, some green perhapes?!) it is most likely that one of the 2 palette rams on the board is faulty (probably the one that is connected to the 3 bits of red output and 1 bit of green). It is a "7489" 16 pin bipolar ram ic and should be located near the rgb output connector on the main logic board at location "2C" next to a few diodes and resistors. Check with your logic probe if the output pins 5,7,9 and 11 are toggeling if they are not - replace the ram.
If you need any more help please feel free to post here - also please report in if you were able to fix your board - then this video would actually have served a purpose.
First of all thank you for your very detailed response!
Pin 7 is in fact low on 2C. However pin 3 is floating on both RAM chips 2C and 1C. Should I replace both RAM chips or does this seem to indicate a problem upstream?
Oh, that would be the write enable of the rams. So that would mean that the palette can't be written into the rams and therefore could be invalid. So don't replace the rams, instead look at the source of the signal to pin 3 (follow the traces). Both pins 3 should be connected to pin 12 of an ic 7410 at 6J. If the output pin 12 isn't floating then theres trace damage between this chip and the rams. If it is floating and the inputs of the 7410 are not (that are pins 1, 2, 13) then replace the 7410.
First I verified that I have continuity between 6J pin 12 and Pins 3 on both 1C and 2C. However, 6J pin 12 is high but pins 3 on both 1C and 2C are still floating. This doesn't make any sense to me. Also the 6J input pins 1, 2,12 are all pulsing.
6J pin 12 high, ram pins 3 floating and continuity between them ok don't go well together. At least one of those 3 facts has to be wrong. Reverify. Alternatively try bridging 6J pin 12 to the rams pin 3s temporarily using a jumper wire to see if that fixes the issue. Be sure to reset the game after connecting the jumper wire.
hI doktorzett
i have the exact same problem on my operation wolf 3 but can't locate what part is the palette
ram, don,t seem to be any board diagrams available online, i am able to solder a new one in
if i new what part it was please can you give me any help
thanks in advance
Garry..........
were do you get your schematics from
I look at your videos from uruguay and they are very illustrative .. I congratulate you for your effort.
In some days I am going to buy a broken double dragon pcb and it is very probable that I need help .. you would have an email for which I can communicate with you to be able to send you information of the error that can have the double dragon that they are going to give me to be able to fix it ?
Thank you very much for your videos and I will keep watching and giving you positive ratings!
Thank you very much, I'm always glad to hear if some people find my videos helpful. If you got any issues with your repair, just feel free to post them right here if you like, I'll surely check back and try to answer your questions if I can.
I know this I an old video but I'm just gonna put this out there, Where would someone find the data to create a new palette rom? I have a crazy Kong board that has a faulty MB7051, even if I could find a chip, I don't know where you get that info. Game ROMs online don't seem to have specific color rom that I can see.
Maybe check hobbyroms.com!
I have this kinda same problem with my WWF superstars PCB but it's blue and some green and letters come on the screen I'm not sure idk witch chip it could be I'm not great at it finding theses at all I get frustrated. I need help 😢
Well if you do have a palette problem maybe just follow the rgb outputs back to the first "memory chip" in line. He could be the problem.
hello, although it's been 4 years I'll try to ask for help anyway.
My Double Dragon has characters that sometimes disappear, can you tell me something to check, thanks.
Hey, maybe you could describe in more detail the problem you are having. That way I might maybe be actually able to narrow something down...