Pac-man original newbie repair

[BadMonkey]

No, that board is long gone. Thanks for info. I put a new harness on and checked the grounds. I re-soldered all the wire connections and cleaned and reattached the other grounds. The ground on the plug to the wall (ac in) is good. It's why I posted this. I appreciate all the info. When I get it resolved I will post my findings in a summary. I am trying to do everything I can to stay away from a switcher on this cab. I put one in tron but I also left the (working) original power supply in it. I am using the battery pack card on the switcher for saving scores. (Was having a problem with the lithium battery saving scores on the ps. Mcr's have givien me a problem. Still have that battery in tapper and it's dead after a day or two. And yes, I added the blocking diode).
Thanks again.

[BadMonkey]

Ok. So I replaced the rfi filter then turned it on. Same wave on screen.
Next I replaced the pcb filter caps (4) from twisted thinking this had to be it. And WA la! Same wave....
I am at a loss. So, I went and got a Nintendo 3ds xl and am pondering my Dilemma on some Mario Bros 2. I am thinking the video board for the lcd is messing something up. Going to put the 4600 back in and see what happens.
Thoughts anyone?
(Now on excite bike on pc 10. More calming)

[BadMonkey]

Status update;
The cga/ega/yuv to 2vga board used for the lcd monitor is not bad BUT,... the plug (and transformer) added for the 5 volts incoming to run the board was adding interference. I put a switching power supply in just to test the 5 volts for that board only and the picture is awesome (for an lcd that is). Some semi-permanent modifications for the wiring and pac man is good to go for a while.
I have the 4600 on my bench to put back in. I am waiting for some parts to be able to re-install and the pacman upright should be good for years. New edge connector, fuses and block, rfi filter and soon to be rebuilt 4600 all matching numbers back in original condition (including paint and t-molding). Some switches and wiring repaired.
Thanks for the advice and input guys.

[iankellogg]

Here is what I am thinking. I just had a monitor on the bench this past weekend that had a humbar that didnt seem to want to go away with the standard cap kit + filter cap.

The voltage regular was not working, it was shorted and was passing through AC.

My guess, and i think this is very likely, is that the vreg on the pacman board is dead. The vreg transistor is the one on the heatsink near the caps. I would do a multimeter diode test on it and i bet you will find its shorted. the transistor is a TIP31 https://iankellogg.com/index.php?main_page=product_info&cPath=17_20&products_id=91

[BadMonkey]

After pac finally being "fixed" it is dead again.
It mysteriously started flashing fruit on the screen. It looks like it is cycling through all the fruit and ending on cherries for a moment then starting again. It's in about 7 spots randomly across the screen.
I thought it was voltage, it is not. I changed the z80. Same. Sync bus, same (although I can't verify the replacement). So, my plan is to change EPROMs and then get out the probe.
Any suggestions?
(Was a bad day. Lost pac, popeye and Mario. Frogger sprite problem just a few days ago).

[iankellogg]

After pac finally being "fixed" it is dead again.
It mysteriously started flashing fruit on the screen. It looks like it is cycling through all the fruit and ending on cherries for a moment then starting again. It's in about 7 spots randomly across the screen.
I thought it was voltage, it is not. I changed the z80. Same. Sync bus, same (although I can't verify the replacement). So, my plan is to change EPROMs and then get out the probe.
Any suggestions?
(Was a bad day. Lost pac, popeye and Mario. Frogger sprite problem just a few days ago).

sounds like eproms to me.

[BadMonkey]

Well, I am using this as an excuse to get a logic analyzer. I have a probe but I have been itching for a new toy. I have an eprom read/writer but I am setting up a new (old) computer as I have never used it. I am a few decades behind the times but as they say 'better late than never'.

[iankellogg]

you aren't going to want to mess with a logic analyzer. Seriously, unless you are working on a nintendo game it isn't worth the hassle. I RARELY pull mine out

[BadMonkey]

Dam. I already ordered it. I was hesitant until one too many beers last night. Lol.

[BadMonkey]

On a positive side (sort of), I have a few Nintendo boards that have flaked out on me.

[iankellogg]

Well which LA did you buy?

And how's your knowledge of DMA?

[BadMonkey]

Agilent 16702 with 16556d card. being as DMA can be quite complex, I would consider myself a novice. I had vocational electronics training many years ago. It is just a fun hobby for me now. My background is industrial maintenance. I usually do ok with my logic probe but I have been interested in learning a lot more. My last bit of gadgetry was a Sencore CR 7000. Something I was not too familiar with but I tested every tube I have with that thing. And it's awesome! I feel a lot more comfortable with it now. Working with it helped me understand monitors and tubes functionality much more. I am hoping to understand the processes on these boards more than I do now. Again,....novice.