Give a good inspection around the daughter card for the EPROM. That is a tough area to rework if there is problems.

80B is notorious for reset problems resulting from solder around the daughter board proms as previously stated.

I would definitely clean that up either way. It is probably where you reset problems came from.

However if the game booted before you began soldering I would go back an check over ur work

There's a bunch of information on pinwiki.com about this.

What you've got there is a fix to the wrong part of the problem.

You have to get the daughter board OFF in order to fix it. It's a single sided board and the connections are cracked on the pins on the underside (inaccessible side) of the daughter board. All 80B games have cracked connector pins on this board with exactly the symptoms you describe. It's broken, but you won't be able to see it until you unsolder the daughter board.

It is tedious work to get these boards off. You want to get all the solder off of the pins and have the board pretty much fall out. My soldering skills are OK and I messed up one of the boards I did this on. Patience is key.

I like the replacement boards that Great Plains Electronics sells. They are socketed so they can be disassembled for inspection, and they mount to two sockets on the CPU board for redundancy. They are double-sided so the solder points are less likely to fatigue and crack.

If you have a battery on the CPU board, get it off. If it is a DataSentry battery, it will already be leaking; if it is not, it will be leaking soon. This is a really good idea, but probably not why your game won't boot.

I see at least 5 capacitors in that picture.

Seems to me, people have tried to help, and have given you the usual smoking gun on these - I'd concentrate on that daughterboard

That's not the battery mentioned above, that's a replacement battery from Radio Shack. I'd still get that off the board with a remote holder.

You may have solved one problem and started a totally new one---this does happen.
Start at the basics-
Are you getting a good 5volts From the power supply?
Are the connectors in good shape?
You may also have misplaced a connector when reinstalling.
Have you done the ground mods?

That battery on the board is probably original, not a replacement. That kind seems less likely to leak. Still, it should be removed. I have replaced these with the memory back-up capacitors and they work very well.

If the daughterboard has not been removed and re-soldered, it's not worth troubleshooting anything else. My working assumption is this: every time you move the board, you crack the solder joints more. So what starts out as a flaky problem turns into a consistent problem.

This ALWAYS happens on these games.

Yes, you're correct -- soldering was done to the solder pads for the daughter board on the MPU. There are then solder joints under the daughter board itself & those are hard to inspect and the daughter board must be removed in order to rework them. Unfortunately that's also usually where the problems are. Be warned though, that board is a PITA to get out of there without lifting pads... even if you have proper equipment and experience, it can be hard getting it removed without causing any damage at all to the MPU.

This is why I was developing a different approach with a board that connects to the TC1 socket. I don't have any officially available, but I plan to get back to this project over the next few weeks and hopefully get a board order sent off. At first it may just be a bare-bones no-led type of board.. just something to help diagnose and/or use as a quick-fix for daughter board problems like you're having.
https://pinside.com/pinball/forum/topic/alternative-gottlieb-sys80b-piggyback-fix-plug-and-play-interest-check

I'd be willing to sell you one of the prototype boards I have for testing your MPU *before* you go at it trying to remove the original daughter board and take a chance of pulling up solder pads. I have a couple extra of the prototype pcbs that are just sitting around. I'd probably leave the leds off it. You'd just need to swap the game ROM out of the original daughter board into it & install it in the TC1 socket. This would at least allow you to confirm if the daughter board is at fault or if it's another issue on the MPU. When I get the official "PIGGYDEUX" boards made up I can offer you one of those for a discount to swap in place of the prototype. Let me know if you'd be interested.

---
http://www.pinitech.com - "Pinball Inspired Technology"
Kits, upgrades and test equipment for pinball machines

To me the 4.89 is on the edge of being to low- most likely not the problem.(where were you testing it?)
Is the reset board hooked up? I would unplug it forever. (it is a little board above the cpu)
Try unplugging everything but the cpu and the display. See what you get.

Pinwiki is amazing!!!! ---- it is very helpful- Just search "Pinwiki 80B"

I think the soldering of the daughter board to the main board is done by hand at the factory and will look different than all the other solder on the bottom of the board. It could be original(just guessing) Soldering/fixing the daughter board is tricky- how are your soldering skills?

It could be a cracked solder joint anywhere on the board.

It could be anything.... it could be the daughter board.... but that is not where you were pushing to get it to boot. I just like to troubleshoot from the simplest first-- meaning cheap and easy.

Test for 5v right at the capacitor you were asking about earlier- you called it C11 (it is C1)
Test it when the mpu is plugged in.

Does the sound board light up when the mpu is plugged in?

Have you looked at pinwiki?

Unhook the reset board. You do not need it and it eliminates one potential problem

Indeed. Disconnect until the CPU works, then replace caps and leave it plugged in. This system lacks a watchdog otherwise.

What is the voltage to the MPU when it is plugged in?

It has a section on boot problems and power supplies. The first thing to check is the voltage going to the boards. It must be a strong 5V. Sometimes it reads 5v until you plug in the MPU then it falls off. This would be a bad capacitor in the bottom of the cabinet or the power supply is bad. I am not saying this is what wrong but it is really easy to check. Before removing and resoldering the daughter board, I would check this.

Please remove the battery from your computer. Fixing battery corrosion is painful and time-consuming.

Minus - side of the cap should measure 0 relative to ground, yeah. 5.05 sounds great.

I don't know why you think the problem isn't in the daughterboard. It's always the daughterboard. They always have cracked solder joints. When they do, the computer won't boot. The symptoms are exactly like what you have now. Even if the problem isn't the daughterboard, it's impossible to tell until it's been confirmed that it's not the problem. And it always sucks, because it's so annoying to work on.

I don't think that work looks factory, by the way. I don't have pictures, but the factory didn't tend to leave flux on it. I would wager that it's hobbyist rework, and it may have been that somebody didn't want to take it all apart, so they re-flowed the joints that they could get at easily. This won't fix the problem.

I really like these: https://www.greatplainselectronics.com/proddetail.asp?prod=140-101 It does two things: first, it mounts to two places on the computer, removing stress and adding redundancy; second, you can just take it off when you want to inspect it.

If you don't want to resolder these (and it IS quite aggravating, even if you have a decent desoldering pump), send it out, and maybe ask for one of the Great Plains boards to be installed.

I have to agree. The solder from gottlieb would have been clean. I thought step 1 troubleshooting 80B is the daughter board.

first get that battery off the CPU board. the date code on the battery is 1st week of 1986. so that battery is almost 30 years old! it's a freaking time bomb, ready to explode. get that off the board like now, before you do anything else.

disconnect all connectors to the CPU board except the power connector (left edge of CPU board), and the right most CPU connectors for displays. (Basically three connectors will be removed, the ones at the lower edge of the CPU board.) Remove the reset board connector (40 pin socket thing) at the top edge of the CPU board. Now power up and check the +5 volts. the power supply is adjustable, make sure it's 5.05 to 5.20 volts DC at the CPU board.

if all is good you'll see stuff on the score displays. (it might complain about the slam switch, that's OK, no worries.) If it's not booting, obviously you won't have any display activity. (this assumes the displays and display power is good.) If there's no boot activity, with the game on, gently "twerk" the ROM board on the CPU board. If anything changes (like display activity), then you have identified your problem. As others have said, the ROM board is problematic, and usually is the first thing to check when the CPU board is not working.

Battery not required for boot. Check pin 40 of the CPU chip after turned on. Is it 5 volts?

If pin 40 from the 6502 is 0 volt then the Reset is active and your CPU board will never boot.

The Reset circuitry consists of a delay circuit (to give the powersupply some time to stabilize the +5V) and an undervoltage circuit which kicks in at about 4.4 volts. If the +5V supply drops to 3.6V as you described the undervoltage circuit activates the Reset signal and you will measure 0 volts at pin 40 and the board won't boot.

A system 80 CPU board draws about 1 to 1.3A, your power supply must be able to handle this. You use an external power supply now?

Marco

I don't think the corrosion at the crystal caused it to fail. Does it rattle when you shake it? Then you should replace it but the best way to test the crystal is to measure the clocksignal with an oscilloscope or logic probe.

Your power supply issue can be caused by 2 issues:

1) your power supply is to weak

2) one or more chips are failing at your CPU board and draw too much current which cause the 5V to collapse (but you did have +5V with the normal power supply didn't you??) You can touch Z11, Z12, Z13, Z14 and Z15....If you burn your finger -> replace them. They buffer the switchmatrix and are sometimes blown by a problem under the playfield, in this case RIOT U4 is failing most of the times also.

Maybe you should try to find a technician who can test your board with a test Eprom. I live in Holland and that is a bit far away but there are several good technicians in the USA who can deliver a decent job.

Good luck!

/\/\arco

if the 5 volts is dropping you have a shorted something (chip) on the board. (Pin40 of the CPU chip being 0 volts also means, as others said, there's a problem in the reset section of the board, which just adds to the problems.) At this point, since you seem to be struggling, i would recommend sending the board to someone that repairs system80 boards.

U4 ~ U6 Always get a bit hot. You're welcome to send your board to Holland if you are unable to find someone who can repair your board. Just an offer

Someone in England also made a very nice redesign for the system 80B board:

http://mypinballs.com/electronics/store.jsp

There is an explanation for that: from the unused ports, the inputs (pin 3, 5, 13, 11, 9) are tied to GND to prevent them from oscillating.

Marco

I am sorry

I've had both bad PROM1's and PROM2's (especially NMC27C16B). When PROM2 is defective, often there is a message "PROM2 missing" at the screen. But your board isn't booting at all which *can* be caused by a bad PROM1.

It is very interesting what happens with the /reset signal at pin 40 when you apply a good working +5V powersupply. If it is still stuck at 0 volts you can isolate the problem to the reset circuitry.

If not the problem can be various....bad PROM1, bad RIOT, no clocksignal, .....

There has been working on your board before....maybe the previous repairman damaged a trace to the U3 (piggyback) socket. Not uncommon unfortunately (board hacks).

Good luck!

/\/\arco

I have seen that many times, it's NOT EASY work for not-experienced people

I totally agree with you.

That's awesome. Never turn it off again just keep playing. No honestly you probably touched something that brought it back. That makes me think that there is a crappy connection somewhere so at least your board is not dead. Is it still resetting?

I wouldn't think so but maybe someone else will know for sure. However, there is nothing like that sigh of relief when it fired back up and you get that glimmer of hope that it will play again. I think that something has been pushed making the connection again. You aren't out of the woods yet by anymeans but at least it's playing again. Step in the right direction

Great news!

You have a flaky connection somewhere on the board. Check the board carefully for cracked solder connections, or possible corrosion in the battery area. (I had excellent luck with that type of battery. I believe that after the mid '80s most of them were not so likely to kill the board so soon, but rest assured that they will do it soon.)

Batteries leak a corrosive gas, but if the board looks clean, that's great.

Or... stay with me here... it could be that pesky daughterboard has a cracked solder connection. Jiggling it has made it work. Jiggling it again may make it stop.

So be careful. Avoid any shaking, such as earthquakes or a big truck driving by. Do not nudge. In fact it would be best if you avoided any vibration, such as the pop bumpers, flippers, or the ball being kicked into play.

the pinball gods have blessed you. stop doubting their presence and just bow your head in thankfulness that you have a working system80 game! those pinball gods look down on me everyday and throw lightning bolts at me. you should be happy that they took your case in sympathy and allowed your system80 to run again. it's a good day.... wish i had more days like yours...