https://www.pinitech.com/products/gottlieb_piggydeux.php

Do the ground mods to the head; I had sound issues till I did just that with my Spring Break, been rock solid since. Sometimes the game would start with no sound, other times no music or with sound but would be distorted.

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Make sure the pins and connectors are in good shape- If I recall Pinwiki states signals for sound go through the A3 connector through the driver board on route to the sound board. I would unplug the connectors next and clean them good with an eraser though I have have gotten aggressive and used very fine 600 grit emery paper too. Pulling the sound EPROMs carefully and cleaning the legs with an eraser is always good.

Question- Did you ground mod the sound board and power boards to a common location along with the MPU and driver board? You posted a picture of the sound board, but it has no ground wire added to it in the picture.

Mine all meet in the center and one wire is attached to the lug on the lower right side of the cabinet where the yellow ground strap comes in with the 1/4-20 nut is to tie it all together.

Just occurred to me; another potential issue could be erratic 5v power, I replaced the pot on the power supply (upper center of the rear board with large heatsink) as it was very erratic. Just touching it would cause the power readings to jump all over, I imagine during game play it was going crazy. Worth attaching a meter to the large gray cap on the MPU board, center top just below the small connector and seeing what you have for voltage.

I have mine set at 5.05V

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Recommended_Repairs_for_the_System_80B_Power_Supply_Board

PBR sells a 500 ohm pot, but it isn't the correct one and I modded my PCB to make it work, was very stable after.

One other item that can cause bizarre sound issues is one of the two rebound switches in the left "danger lane" could be stuck. This will cause the danger sound and music to trigger which overrides everything else. Mine was twisted and making intermittent contact causing all sorts of interesting sound issues.

Not related to display, but sometimes you are dealing with 2 problems instead of 1.

The reset section -within the battery corrosion zone- isn't looking very healthy and needs a rebuild imho. Can u post a close up picture from this area?

For the 500 Ohm pots at the 5V power supply I use these styles

500ohm (resized).jpg

They fit like a glove on these powersupplies. Be sure you buy these with the pins in a triangle format, as they are also available with the pins in a inline format.

Be careful when using the power supply's heatsink as a ground plane. It is barely isolated from the 5V output from the LM338K regulator which is the metal housing. And just a tiny shim isolates this housing from the heatsink. Using the heatsink now as a groundplane creates a potential short. The way GDonovan created a "starground" is the better way to do this. You can also use the yellow ground strap as a common point to ground your boards.

Again, the whole reset area of you CPU board is looking very poor and can be the reason your CPU board is having problems to start properly.

Ah, no.... I mean the top section (as it is mounted in the backbox) from the CPU board where the old backup battery was mounted before. Right under the power connector. All these components look affected by a leaking battery in the past. This circuit is the reset section: it comprises a undervolt protection and a delay section which allows the 5V voltage to stabilize before the CPU starts to execute the gamesoftware. The connector itself can be affected too.

The reset board you are referring to is better called a watchdog board: it monitors the Interrupt (IRQ) signal which is a sign the CPU board is running properly. If the IRQ signal stalls due to a hangup/crash it will reset the 6502 processor which will try to execute the gamesoftware again from zero.

1) The aluminum looks to be anodized which is a poor conductor of electricity which is why I didn't use it as a common spot, just asking for trouble. If you were to use it for grounding you would have to grind the coating off first. Better to have it join at a common location with good conductivity and avoid any possible issues with the regulator to boot.

2) From my "star location" you can see one wire vanish behind the MPU board, this one runs down to the bottom right location where the yellow ground strap is so the boards are all tied into the ground circuit.

Was still working on the unit and had not plugged it back in yet.

My pleasure! Glad to have the opportunity to "pay it forward"

Gary

I would check the voltage first before replacing the part.

Large cap at the top of the MPU board, you want to see a tick over 5 volts. 5.00-5.10 at most. When the meter clipped on the cap legs tap the cabinet in the location of the 5V supply and see if it jump around.

I was doing some research over Pinwiki and noticed that it states the florescent lamp starter can make some boards angry causing boot issues, try removing the starter (silver can in socket near lamp on right side) to eliminate it as a possibility.

If so you can replace with a 2' foot LED bulb that operates with no starter, thats what I do on all my pins.

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It should not interfere with booting, far as I know it just keeps you from losing top scores, credits and some bonus features.

If you are good at desoldering/soldering, you can eliminate the need for batteries with NVRAM. https://www.pinitech.com/products/5101_nvram.php

How does the misboot happen? Is it attempting to boot and then resetting?

Did you try flexing the piggyback daughterboard on the MPU? Very well known point of failure on those boards. Just pressing on it a bit in various places and wiggling it a little bit should help identify if that may be the issue or part of the issue. Cold solder joints on that board affect the ROM from being read correctly which can cause a lot of issues. You could try flexing the board some once the game does boot successfully. If it resets then there's probably a cold solder joint there.

If you do happen to have daughterboard issues or want to rule that out, I sell a plug-and-play fix for that (no soldering).
https://www.pinitech.com/products/gottlieb_piggydeux.php

I found the sweet spot on my old original daughterboard that will allow me to boot the game and it will freeze the game once I let go. Time for me to get one of those for my Gold Wings along with more NVRAM, which was easy enough to add into this game (yellow box) with some de/soldering!! 80B (resized).jpg