Rampage graphics issue.. HELP!

[BozoTheClown]

I don't have a logic probe and I've never had a need for a burner. I've worked with folks here for the couple of occasions I've have had a need for burning, and for the small scale its cheaper than buying one. Similar to others, the machine worked great until it's previous owner moved it to get it ready for selling. My new chips are already in the mail and should be delivered Saturday.

 

[BozoTheClown]

Update:

Roms came in a day early and I had some spare time tonight so I got to work. Being very methodical I replaced each of the 6 graphics related chips one at a time, reinstalling and testing the board in between each one in hopes of pinpointing the issue for others. Unfortunately after replacing all 6 the issue remains. I still have 6 additional freshly burned roms for the rest of the boards that I can install, but I figured I would post my findings so far as I don't have high hopes that the other 6 with have any impact either. Additionally I will be away most of tomorrow helping a friend work on some of his machines so I doubt I will have any time. Thoughts? I'm essentially at the end of my troubleshooting skills and my next step will be to try and find someone here that can repair these boards unless someone else has any good ideas.

 

[wugly]

try piggybacking ram chips on the board and see if you get any change. also invest 25 dollars for a logic probe and someone can talk you through it

 

[BozoTheClown]

I don't have any spare PCB boards. A couple of sound boards but that is it. I swapped out the 4 sound eeproms this afternoon without any change (not that I expected one). I also tried swapping out pro-0 and pro-1, but that caused the board to boot to complete garbage so I had to remove them. Perhaps because the replacements were version 3 and the originals were version 2. So with 3 of us having the exact same symptoms, there must be others out there that had this issue and corrected it. Beyond that, who can repair these boards? I've spent enough troubleshooting at this point that I would be content to have someone repair it for me. Especially if the fix can be shared here for others to gain the knowledge of what the root issue is.

 

[mecha]

I bought a parts/untested board a few months back off here and it was actually missing one of the ram chips. just booted to garbage. I sourced one off the good board at work and it came right up. so I would suspect that the rams on these probably go out. if I'm not mistaken they might be the same kind that Qbert uses. I can check this later. I have a couple Qbert sets that don't work at all and I suspect it's probably bad rams.

 

[BozoTheClown]

As long as I have a general idea of what to order that wouldn't be a big deal. Thanks!

 

[BozoTheClown]

I reseated 9 ram chips as identified in the manual as well as 6 additional chips that happened to be socketed as well. No changes. If someone who has a better understanding of schematics than me could point me in the direction of which chips could/should be replaced with new I will certainly give it a try. Offer is still out there for someone familiar with repairing these boards to contact me.

 

[JRudebaugh]

I reseated 9 ram chips as identified in the manual as well as 6 additional chips that happened to be socketed as well. No changes. If someone who has a better understanding of schematics than me could point me in the direction of which chips could/should be replaced with new I will certainly give it a try. Offer is still out there for someone familiar with repairing these boards to contact me.

This is where the logic probe comes into play

 

[BozoTheClown]

Probe showed up in the mail today. What's next?

 

[mecha]

Probe showed up in the mail today. What's next?

connect red probe to +5 and black probe to ground. start tinkering around with touching the pins of the rams. you'll probably need a truth table or something, unless of course you find any pins that are completely dead. that doesn't necessarily mean the chip you just tested is bad though, you'll have to go to the next chip in circuit with the dead pin to see if it's all outputting.

there are videos that show how to use a logic probe correctly, which I have to dust up on. I only recently found my probe again many months after I watched said video.

I watched this one from OneCircuit https://www.youtube.com/watch?v=7l039y8dX5A

 

[BozoTheClown]

So I just ran the probe down all the chips that I could identify as ram chips from the manual and couldn't find any dead pins. Its hard to work in the cabinet and my eyes are crap at the end of the day so it's always possible that I overlooked something. Any additional suggestions? I haven't been able to find anyone here that works on Rampage boards and the only place that I have found online so far is Eldorado Games which charges flat rate repair fees. That one sounds like I'm going to get overcharged since the game is 95% working.

 

[wugly]

look up the data sheet for the ram chips on the internet. the data sheet will tell you what each pin should be. if it is vcc then that is constant hi gnd is constant low. make sure the address lines are pulsing and the data lines are pulsing. if they are constant then that is a good sign the chip might be having a problem.

 

[BozoTheClown]

I'll try to rearrange the board a little better tomorrow and try again with datasheets in front of me. I've looked up one so far (6116) and there are 3 pins that you didn't mention.

Chip Select - Write Enable - Output Enable

What should the reading on these be?

Additionally, should I have my probe set for CMOS or TTL? I've done some extremely brief reading and it seems that as long as I am working on 5V boards (most of them) that I would leave it on TTL as the CMOS setting it for boards with higher voltage than that?

 

[wugly]

well I can tell that you are flying blind but willing to learn so I am going to pull on some flame retardant clothing and give you some theory on how I understand it and hopefully others will correct my mistakes.you have a video problem. Video consists of the background image and sprites which are like cartoon cells that get flashed on different parts of the screen. the screen gets redrawn many times per second so that when looked at the changing sprite images which change between refreshes seems to move or change. originally all images and programs are stored in the roms which are like a thumb drive though not as big. we can tell some of it is working because the program loaded and is running. background images are retrieved and stored in ram. sprite images are also retrieved from rom and are loaded into ram in there appropriate space. sprite images can be changed from one screen write update to the other. both ram memorys are sent to a ttl circuit that combines them into a video write. it does this by writing the background video for that space unless there is sprite data and then the sprite data is written instead. Now on to your problem and that is that your background is being written fine but your sprites are distorted.
Possible Solutions. bad eprom (not replaced) bad data buss entering or exiting eprom. Bad Data buss going to ram chips. bad ram chips. bad ttl chip that mixes the data or corrupted data.
We know your rom chips are good because they were replaced with good ones.
You are testing the address and data buss from the ram chips with the logic probe now, you are making sure that none of the pins is stuck in a high or low state with the exception of the vcc and gnd or that no pins are floating with no connections. This proves that there is no catastrophic failure in the chip or on the buss that is causing a problem but it does not prove if the chip is storeing correct data. ways to check that are use a fluke with a processor pod plugged into the board and directly write to chips and read them (hard to find and expensive. Next remove ram chips and put them in a tester. Or my favorite is to get a few good chips and place the legs of the new chip on top of the chip being tested while the game is running. if the chip is good then the two chips will work together and not fight with each other and nothing will change, but if the chip is not storing correct data the chips will fight and you will see the image on the screen change as the chip is removed and added. Does this help you?

ps save the old rom chips to put back in to test after you solve the problem because the new chips are still useful as spare parts when reprogrammed

 

[BozoTheClown]

That definitely does help and is well timed as I just got home. I'm going to go do some more probing and will report my findings back here.

 

[BozoTheClown]

2018 2kx8 45ns chips located at 11G, 10K, 9J, 11J
All of these tested identically, but I was showing low on 19, 22, and 23 as well as high on 16 and 17. My understanding is that all 5 of these pins should be pulsing.

2018 2kx8 55ns chip located at 10C
Tested low on 19 and 22. I believe these should be pulsing.

6116 2kx8 120ns located at 11B
Tested without issue

6116 2kx8 150ns located at 6B, 9B
6B tested ok.
9B tested low on 19. I believe this should be pulsing.

93419 64x9 located at 4A
4A tested ok.

Thoughts? I find it hard to believe that all the 2018 chips would test the same yet all be bad. What do you all think about these finding?

(FYI, all RAM chips are socketed )

 

[wugly]

on the 4 chips 16 and 17 are tied together on a pullup resistor with no other connections to them pins 12 19 22 23 are tied directly to gnd and should be low

10 c pins 19 and 22 12 tied to ground so they are low

9b you got me there can not find it in schematics but I think it should be tied into 74ls157 and it should be changing

 

[wugly]

I would track down that anomaly at 9b but I would also test out the memory chip ability to store proper information by piggy backing a known good chip on top of a test chip and look for any changes in graphics

 

[BozoTheClown]

I don't have any chips on my shelves. Out of my dozens of games, this is the first one I have had to dig this far into myself. I might have to ship it out after all then.

 

[BozoTheClown]

wugly has been assisting me via PM but we haven't made any earth shattering breakthroughs. I have my logic probe and am able to test things now, does anyone else have any suggestions?

I have also ordered an actual manual with schematics from ebay as all the PDF scans I have found online are really bad and the schematics portion is nearly illegible. Should have it early next week.