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Double Dragon Arcade PCB - YOU do the repair! - Part 1
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- čas přidán 27. 09. 2022
- This time YOU do the repair! Please post your suggestions below!
You can find the schematics here:
www.arcade-museum.com/manuals...
Thank you!
Beautiful lab work
Top priority is to clean up the PCB corrosion and make sure tracks in the affected areas are sound. Then I would look to ensure the CPUs are running. I know you said the clocks are good but it’s easy to check if the CPUs have a clock and there’s activity on the address and data lines. Having just looked at the schematics I see that it is using 6809 type CPUs which have a quadrature offset clock mechanism rather than a simple clock so there’s more to go wrong there.
Going by your getting video sync i would next check to see if your getting the correct sync output using scope, if so then check clock and reset signals on main cpu, If the cpu is running then i would be looking at the video ram which is located on the top pcb, From memory they are a 6116 and if that is dead will give what you seeing on the screen, Remove test and replace if faulty should get the game to show the ram rom test to see if it locks up on any of the following. My guess is after this you will hsve the famous 63701 which usually is caused by the 6116 ram next to the it, After checking and if found faulty replacing it should get the game to boot into the demo screen to see if it has any other issues,
Cleaning up the PCB should be the first step, yes. Usually this doesn't improve anything, but sometimes, you never know. That said, if clocks weren't present there would be no sync signal. The board isn't resetting, either. I'd check activity on the CPU, then look at the reset circuit. From there I'd check the connections of the main program roms, then their contents. This was just a stream of thought comment from someone with little experience but likes this stuff a lot. :)
me to
Mister Retro Wolf says try and look at the clock / sync first, even if you think it looks ok. If that's ok, then on to the inputs to the CPU - like a RESET, maybe it's being kept low somehow.
step 0ne.. clean lol even though you have a theory on clocks being present.. I would still start by checking all working clocks... is the CPU being clocked? move to other CPU signals.. interupts, and reset line... my guess is either the CPU has no clock... or the CPU is dead
Hey Shaun! Thank you very much for your comment! I am a big fan of yours and watch all f your vids! ;-) Seriously. You are doing a great job on your arcade repairs! Great to see a contribution from you in my video! Makes me happy.
Think as a first step I would look for any physical damage to the board. Then I'd pull all the socketed chips. Dump the roms to cross check them through romident. And clean up any corroded looking legs with a fiberglass pen. Before re-seating them again.
First, I would be interest in this and see how i go, First i would check for any track rot, these boards suffer bad track rot, Next i would check the clock circuit and see if its workiing correctly
Remove, clean and reinstall all the removable program ROM IC's and check socket to board continuity.
Maybe a counter section that computes the VRAM addresses to be sent to the video DAC?
An interesting concept for a video series! 🤔 I don't know much about these particular boards but I would assume that they have a watchdog circuit however it does not appear to be "watchdogging". Standard practice is to first check board voltages at all relevant points but certainly the CPU(s). If these are okay then check clocks and reset/halt pins. Then, as per your last video, check for activity on the CPU address and data buses. 👍😁
Yes the pcb corrosion area would be my first check and clean up.
i would start with the cpu's. See if they all get a clock. If they are halted or someting. if all lines are toggling as supposed.
Nice idea
I have super breakout 2 years
Unsuccessful repair.
What can I suggest 🥺?
Rusting on ROM IC legs is immediately obvious - but thats something to check later. I'd start by checking all the power rails (from experience with ZX Spectrum repairs I consider this the most important first step because certain DRAMs such as 4116s etc. will be damaged if not powered correctly) - then I'd move to probing CPU for activity.
Do you have a 68K POD for your fluke? I would start with that. ROM Verification and RAM verification via Fluke.
1 vodka time! then 2 check corrosion on under side maybe disrupting the sync signal