Looking at the connectors, there's nothing that should be carrying significant voltage. So, that's good, at least.

https://pinwiki.com/wiki/index.php/Williams_WPC#WPC-089_Signal_Map_.28pinouts.29

pasted_image (resized).png

The top LED (D19) is stuck on, which it shouldn't be.

https://pinwiki.com/wiki/index.php/Williams_WPC#Power-On_LEDs_and_Sound_Tones_.28Bongs.29

That means the blanking signal isn't being pulled low like it should. But the signal passes through several components before the ASIC's blanking signal reaches the LED, so there could be a potential problem along that path.

So, go right to the source--check the blanking signal at the ASIC--is it low or high? If it's high, I would guess something could be wrong with the ASIC, since most of the pins from the swapped connectors lead into the ASIC. It's possible something exceeded the voltage tolerances of one or more of the ASIC pins and killed it.

I would be tempted to pull the ASIC and install a spare (if you have one) or swap one out from a known good one.

If the swap has no effect, I might also suspect the CPU chip. And if not that, then the ROM. But, it might be easiest to do the ROM first.

Any time you swap components, just be aware that there's the risk that the good component might fail after being installed in the problem board.

Any other WPC experts want to weigh in?

I would remove all cables from the MPU except power and see if it boots correctly.
If it does, connect the ribbon cable to the power driver.
If it boots, add the ribbon cable to the sound board.
If it boots, add the cables for the DMD board.

If the process fails at any point it gives an indication of where the problem may be.

Did you install a 6264 NVRAM? That is the most common one used on this WPC MPU board.

On a rare occasion, I see a 62256 installed which the jumper configuration would be different for that one.

Checking pin to adjacent pin all down the line on the NVRAM socket looking for a solder short is the next step.

Can you post photos of the back and front of the board?

@THE_PUMP_HOUSE, This sounds like the next step

With seemly no damage originally found, just apply 5v, 12v, and ground to the power connector to see if it boots on the bench or just plug in the power connector in the game. If it boots, it will save you all that time doing continuity testing.

This is not entirely true. There are zero series resistors between the ends of the ribbon cable and almost every other pin is ground. Shifting a ribbon cable off by a row will possibly short every single output of a chip and maybe some ASIC signals to ground. When the chip tries to drive high it is a dead short and that is no good for the chip and is able to blow out a chip. Done it myself between the driver board and MPU, whoops. Board to board data buffer fried I believe.

If you just swapped the two 26pin plugs, but had the polarity correct on all ends, it should not hurt anything but you would still ground out one signal, DIS4 I think, which would probably be used in enabling the aux driver board flashers. I believe that goes right to the ASIC with no series resistors or chips between. Hopefully grounding out that signal is not going to kill the ASIC. Considering how rarely the ASIC fails, its probably ok.

Remove the NVRAM from the socket and try again since that is the last thing worked on. Triple check the work around that socket. Even though it booted up once with the cables shifted, i'd still expect the most recent rework. Might have had a flaky joint that went open when the board flexed messing with the cables.

"If it 'ain't broke - don't fix it" says Alfred

Do you have the chip you desoldered? Any copper rings stuck to the chip legs?

Am I seeing some prior battery damage? the bottom pads of the resistors to the right R88-89 look to be corroded. if this is the case, maybe there is more that needs to be looked at on the board.

No, that's just some shadow and possibly imperfect solder joints. The area looks clean to me.

Your solder work is so much better than most of what I see!

I've gotten lucky, when I've misplaced ribbon cables nothing has blown up, so I suspect this is something else.

Of course, the terrible not-so-secret about board repair is that some of them take insane levels of dedication to find the problem.

I've had a number of the WPC CPU NVRAM replacements go bad on me, so, as you are doing:

Trace every connection that goes to where you put in the socket, make sure you ARE connected where you should be.

Trace every connection on the NVRAM socket and make sure nothing is bridged, make sure you ARE NOT connected where you shouldn't be (at least on the RAM socket itself).

Then substitute components.

The first rule of substituting components is that the best way is:

Test the suspect part in the known good system.

So if possible, pull your NVRAM, put it in a known good system (board), and see if it causes a problem there.

It's rare, but I've had bad NVRAM chips fresh out of the package.

Then pull the CPU chip, and put it in a known good system (board).

Then pull the ASIC and put it in a known good system (board).

(Edit: Probably need to think about swapping the ROM chip here also...)

Once you have known good components, then you can start with VERY basic board problems. Power, Clock, Reset, according to the 'My CPU is dead' troubleshooting, I start by re-reading Leon:

https://pinwiki.com/wiki/index.php/Leon_Borre_WPC_CPU_board_repairs

A fair amount of my 'OMG, why won't this work!!!' boards have been bad ASIC sockets. I personally send these off to a technician who is more experienced than I am at working with these chips.

Tough troubleshooting here!

Let us know what you find!

The top 2nd and 3rd pins from the top right on your NVRAM socket may just have solder flux covering the traces close the pads, but they look like broken traces.

It also looks like you have all 4 pins in the picture with broken solder joints on the ROM socket.

Screenshot_20220718-115015 (resized).png

With the broken solder joints on the ROM socket, I would remove much of the old solder and resolder it. It is always best not to mix old solder with new solder. I don't think you need to completely remove the ROM socket.

Where did you purchase the nvram?

Did you receive Ramtron branded ICs - i.e. did you order https://www.marcospecialties.com/pinball-parts/RAMTRON ?

I've bought about 300 FRAM ICs the past couple of years from reputable big box electronics merchants. All of them SOIC-28 (can't find new DIP-28). All of them Cypress Semiconductor branded.

https://pinitech.com/blog.php#1519

Caveat emptor.

How long ago were they bought? If recently, maybe Marco will exchange them. Worth asking.

I use Pinitech or Andrew's (Weebly)

Zero failures and great tech support by both.

SRAM chips have the same operating voltage range as FM1608 and most NV modules are built around the W version of FM1608 which is the "wide voltage" version which will operate down to 3v. Starting at system 11, maybe 9, they should have low voltage drop diodes

If you have NVRAM chips that are failing within a couple minutes, Marco might have gotten burned by fake chips. Would not be the first time that has happened. The FM16L08 is a 3.3v version and will not work very long at 5v. I also read a while ago on Cypress's website about failure analysis showed a FLASH technology chip remarked as FeRAM. It worked initially but had very low endurance.

I had to replace the 1n5817 on a whirlwind with a jumper because the nvram (I don't remember which one but it was a LONG time ago, like repair connection days) would sporadically lock. I made it really obvious that there was NVram installed (pulled battery holder and wrote in sharpie NVRAM INSTALLED AND JUMPER) in its place.

those things have a built in voltage supervisor. I could see them being more picky about the 5v.

This would explain why when trying to troubleshoot a system 11b with a test Rom and a brand new nvram 5101 from Marco with a ramtron chip after a few minutes of having the test Rom running and it telling me the ram has an issue (didn't want to believe it was the chip itself since it was new) the chip went up in smoke! I ended up giving up on that repair after replacing the chip with one I got from mouser. I told the owner to send the board to someone who asked a flat rate for repairs because I didn't want to afford buying more parts if they were going to go up in smoke. I was really really bummed that night not understanding how the chip could have burned.. I started looking into my psu but only the ram blew up, a few minutes after ever trying a test Rom on a system 11b.. And my psu didn't show any signs of failure.