(Topic ID: 289473)

Gottlieb System 80 won't boot - stuck IRQ

By goingincirclez

3 years ago


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#1 3 years ago

Just joined and posted this in the Black Hole club but this might be better as its own topic. For what it's worth I have pretty good proven experience resurrecting complete wrecks and rebuilding boards in WMS Sys 6/9/11, Bally/Stern -35, and GTB Sys3... but this (BH I just picked up that hadn't been put together in years) is my first System80.

Current state:

I am aware of the ground mods and am implementing them but want to get the game to boot first. So I've grounded the MPU, Driver, and Power Supply, down to the ground strap. I added the extra wires to the MPU / Driver interconnect. The MPU has the "slam switch mod" added. I've verified proper power (5 / 8 / 42 / 60) at the power supply. All fuses have continuity. Transformer voltages look good. Rectifier voltages look good. I added the 5V status LED to the MPU and that lights up.

What happens:

- At power on, (most of) the Playfield GI turns on but there is NO backbox GI aside from the chase lights (yay, aux light board works). Wait a few moments and maybe you'll hear attract speech (yay, speech board works!). But there are NO no controlled lamps / attract mode, no score displays*. I get the playfield "coil thunk" momentarily and that's it.

(*Score displays are actually about 50/50 odds of them being all blank, OR three of the four illuminating a couple "half characters" like backwards little c's instantly. BUT when I turn the game off I can briefly see all segments on all four displays light up right as power drains... so the displays are hopefully/probably good). Occasionally there may be a couple controlled lamps stuck on but like the displays or activation of the sound card, this is inconsistent.

Clearly the game isn't booting... but I don't think that's the only issue.

Further troubleshooting:

6502 chip is high on pin 40 and pulses clock signals on pins 39 & 37. All 3 RIOT chips share the pulse on pin 39 too. SO that means the reset circuit is working. But when I check IRQ on the CPU p4, it's stuck high.

Unlike posted guides for WMS and Bally/Stern, there doesn't seem to be much posted on troubleshooting these. It's all "do the ground mods and there you go". Not much in the realm of further or basic troubleshooting... not even to answer if the MPU would boot without the Driver board attached...?

I do have the schematics and can make some general sense but am still likely to miss things. Can anyone help with guidance for tracing signals, next chips etc, to figure this one out..? Thanks....!

#2 3 years ago

Morning bump...

Also to add: I do have a ROM burner (not the greatest one but it's worked so far on other projects). I've read that a stuck IRQ can point to a faulty game ROM. So I removed the PROM - which appears to be original - and compared it to a ROM file I managed to find online. It passed verification, but I attempted to "reburn" it just in case. Either way, no change to the MPU boot: IRQ is still stuck high, but RDY and clock signals seem present.

#3 3 years ago

Heh, why do I have a habit of creating tech threads that nobody responds to? I must be "The Stumper"!

I figured out the missing backbox GI thing - the first time I've ever has a fuse "beep" (continuity test) good, but actually be bad. So that was stupid hidden, but easy enough.

But as for the machine boot: still no displays, and still no full MPU boot: it's still stuck on CPU High IRQ. I managed to find Clay's System80 guide on the wayback machine, which is a little more in depth for troubleshooting this than pinwiki (no offense Chris, I know it's always a WIP!). What Clay said about high IRQ is usually this is due to a bad PROM, but I think I've ruled that out in the previous post.

He also says there's a way to get the game to go into a gimpy test mode WITHOUT a game prom installed, BUT my MPU won't even boot that far. And still missing displays is a key indicator.

So next step is looking for activity on the CPU address/data lines: they are all dead. Clay further said this could be due to a bad RIOT chip, but of course I don't have any, nor would I know "which one" of the three. Hell, maybe the one for the displays is out. Before I go chasing one or more replacements down,, is there anything else I should look for? All the address lines tone out cleanly from CPU to RIOT to PROM. I am testing the CPU on the bench at this point (the slam switch is jumped closed).

Anyone? Bueller? ChrisHibler ?

#4 3 years ago

Yes, you can boot system 80 mpu boards on the bench/in a game without the driver board connected.

The IRQ signals on system 80 are completely controlled via software, there's no hardware timer like all those other systems (bally, stern, williams, etc.) - until the timers in the RIOT chips get programmed, there's just not going to be an IRQ. And NMI is tied high, so no interrupts there.

Gotta go super simple here..... reset signal, clock signals, test as many chips as you can. Leon (RIP) has a system 80 test chip at pinwiki, and I know there's another test chip I got somewhere, but I've never had to use them.

You can do a lot of work on the bench if you haven't verified the power supply as working 100% as of yet, much easier that way.

I think one of the larger issues IIRC all the RIOTS have to be working, period. No swapping one to another to isolate something, they all get programmed for something essential to the machine's normal operation. So without known good working 6532's (which also have the system ram....) just not going to work.

#5 3 years ago

Well, knowing all 3 RIOTs have to be good or else, is a step! I honestly have no idea if they are, and there doesn't seem to be a good way to test them. But I'd think there has to be, right? They are $13-15 ea from places that have them.

The game's power supply is putting out nice voltages across the board. My bench supply seems to be low but is enough to get the board going (I'll probably replace that supply soon).

I tried a Leon WMS Sys6 test rom years ago but wasn't able to make much sense of it then (granted, the board had other issues that probably weren't helping). I recall that section on pinwiki, maybe I should read up but with my luck it needs some PROM I don't have either, ha!

#6 3 years ago

Welcome to the adventure that is System 80.
Scott (above) is 100% correct. All three RIOTs need to be working almost 100% for the board to boot.

IRQ staying high means that the processor isn't running enough to have the RIOTs doing their jobs, including interrupting the 6502 when necessary.

I have Marco's test ROM that I use with a PiniTech board that plugs into TC1.
I also have Ed's (GPE) QuickScan80, which is NLA.

I mostly use Ed's QS80. It tests the RAM and all three RIOTs.
Most frequent reasons for failure to boot...
...failed reset section
...failed clock section
...blown U4 (switch matrix). You can diode test Z11-Z15. If one of those is blown, there is a 50/50 chance that U4 is blown.
...failed 6502
...failed U2 or U3
...failed RAM

If you'd like to send the board to me, I can take care of it.
Otherwise...Happy Probing!
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#7 3 years ago

Hi Chris,

Thanks for the advice. Yes, Sys80 seems to be quite the different beast than the other boards I've dealt with but I knew that going in, and wanted the challenge. I guess what I didn't expect is for the near-shotgun approach to things, though. "All three RIOTS need to work... but there's no hints toward fault so WHICH ONE(s) are you gonna mess with first, punk? OR maybe it's those U2/U3 ROMs too, which are NLA..."

At least in your checklist, I seem to have passed the reset and clock sections. U4 RIOT may be suspect. It's not "hot" but yesterday I noticed someone marked it with an X in pencil, so I went ahead and ordered some 2532's from Jameco. Meanwhile I'll run those Z11-15 tests. A few had been previously replaced.

Either way it seems the chips I may need to buy could add up to the cost of a tester, so it might be a wash if I get lucky. I really want to say I did this one myself - with assistance from wiser folks than I of course - but if it defeats me you'll be the first one I call!

#8 3 years ago

So after probing the Z11-15 chips with the "diode test", I found that both of the 7404's (Z11 and 12) were fishy - each had a dead (open) pin. Z13, 14, and 15 checked fine. I replaced Z12 and now it reads properly. But the new 7404 for Z11, pin11 reads low when in the board... and that is connected to the RIOT at U4. So maybe that's another clue pointing at the U4 RIOT?

I went ahead and removed U4 and when that chip is gone, Z11 reads normally. I installed a socket for U4 and replaced the chip, and Z11 p11 is low again. SO there is definitely a relationship there. Maybe it's normal?

Unfortunately, even with the new 7404's, the IRQ remains stuck high. Guess I need to wait for my replacement RIOTs.

#9 3 years ago
Quoted from goingincirclez:

Unfortunately, even with the new 7404's, the IRQ remains stuck high. Guess I need to wait for my replacement RIOTs.

I'll warn you up front -- I don't have any advice that's going to help you in this post, but I wanted to share my (very short) System 80 experience.

I plugged a microcontroller (ESP32) into TC1 and wrote a program that would single-step the processor (using Steve Wozniak's 6502 single-stepping approach). It was fun, and I was able to watch the address, signal, and data lines as the processor tried to boot and then ran into a RIOT issue and then vectored off into nowhere (for a reason that I still don't understand). I replaced the RIOT in question, got a little farther, found another issues, etc.

I ended up doing every ground mod, replacing a couple of ICs, and getting the thing working for a solid few months. Then, I started having intermittent boot issues and the occasional hang. For a while, I ran the machine with a board I made plugged into TC1 that would watch for hangs and reset it. I think some machines had this done in the wild (I've seen it in pictures, but I've never encountered the board IRL).

The week I bought a replacement MPU and sold that machine was one of the happiest weeks of my life

One of my friends buys & sells the machines I work on. I told him that if I see another Gottlieb, I would dissolve our partnership.

I don't regret that time, but I believe those boards are straight-up haunted.

All that said, the next machine coming here is Hulk. I already believe those System 1 boards are unfixable.

Best of luck though - I'm sure you'll get it straightened out!

#10 3 years ago

LOL that story doesn't exactly inspire confidence, but I appreciate the vote of... confidence?? ha ha

I have some progress to report, en route to more maladies. But first, progress!

I noted the hint about the Z5 5101 RAM causing a no-boot scenario even as it's not implicitly needed to boot. So I pulled it and... got an IRQ signal! Added a socket, still had IRQ! Put the pulled 5101 back in and, IRQ stuck high. Swapped in an NVRAM module I had and IRQ came back. Huzzah! And signals on the Address and Data lines, yay!

BUUUUUT all is not well just yet: it still won't boot reliably because the IRQ goes away (held low) after a while. And when connected in the game, it doesn't "boot" right away if at all, because the displays don't light for over 10 seconds if they ever do. (Yet, I have finally seen all the score displays light with all zeros, so that's progress... but the credit / ball displays said "11" at the time so what does that mean?). Even with a "full display boot", after a few more moments the system crashes, display digits disappear and IRQ goes stuck low.

I've not connected the driver board yet because I didn't want to push my luck too much. Given the above, that's likely a wise move as something is still sick: probably a RIOT and most likely U4 if I'm understanding published advice. Guess I need to wait a bit for my replacements to arrive. But hopefully this is an encouraging sign...?

Oh and P.S. to Chris: I forgot to reply, to your mention endorsing the QS80... I guess you hadn't seen my other topic before that, d'oh!
https://pinside.com/pinball/forum/topic/looking-for-a-gpe-quickscan-80-to-borrow-or-buy

#11 3 years ago
Quoted from goingincirclez:

but the credit / ball displays said "11" at the time so what does that mean?

Nothing. That's just random.

Here is the other option. Currently not available either....
https://www.pinitech.com/products/gottlieb_universaltester.php

I remember the bad old days when I didn't have these test aids. It's a tough road to hoe.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#12 3 years ago

I'm beginning to think this damn board is haunted. There's just nothing consistent about it.

So my last update, after getting signals on IRQ but nothing lasting: I decided to really inspect and clean the board looking for tiny shorts, etc from previous work. Didn't find anything obvious. When reconnecting to bench power... stuck high IRQ on power-on. Or, flips low after a moment and sticks. OR - rarely - it might give some weak noisy pulsing for a few moments before locking one way or the other. What the heck with the randomness? The 5101 is gone to remove a variable. And I added the pullup resistor on CT1. No fix either way.

I finally waited for the new RIOTs (I only ordered two) to arrive. I first replaced U4... and noticed that the odd reading I was seeing on Z11 went away too! Was that the issue after all? NOPE. Same behavior. But after powering on and off a few times, I finally - for one glorious power-cycle - got a steady IRQ beat for a few moments! A little noisy, but it was enough to make me chase and trace behavior on other chips and pins until it crashed (as I expected it would). So no fix... but I noticed that U4 was much cooler! I never considered the old one "hot", merely "warm"... and yet the new one was barely anything. So, since the original U5 was similarly "warm" I replaced it with my second new RIOT. That didn't fix the boot IRQ issue, but U5 is now cooler too.

Hmm. What next? Z11-Z14 had all been replaced. As had Z17, Z24, and Z26, and 21. I replaced them again (checking and replacing old sockets and workmanship), no change.

I saw references to Z15 affecting the swtich U4 RIOT, and that being original I finally replaced it with one I pulled from a dead Sys9 board. When I turned on the board, it immediately had an IRQ! For about 5 seconds. Then it locked low. And it's basically "mostly" but not "always" started low since. Haven't got an IRQ since and at this point I feel like I'm living in a dreamland, who the hell knows what this thing will do. There's nothing consistent about it even as I've methodically followed the advice and hints I can find.

Would something in-board have killed the 7432's at Z15 an undone my progress?? What else is there to look at / for?? Have metered the chips and they all look good but who can say for sure at this point? Sigh.

#13 3 years ago

So, did I say the board was haunted? I'mma stick with haunted. But maybe more of the benevolent type for now? Because the DAMN THING IS BOOTING NOW! Yay?!

So here's the skinny. I posted the previous rant in rush on Sat AM with a full 12+ hour AFK day ahead of me, hoping maybe someone might see and set me straight while I was gone (heh). Meanwhile, I did have the opportunity to swing by a friend's place to pick up a spare 6502 and 6532 to have for swap-testing if need be. I got home late Saturday with those parts in hand. Went back to the board and looked it over AGAIN not seeing anything new. Took my "new" RIOT out of U4 and put my buddy's part in, turned the board on: no change, not surprised. Yet for reasons I'm not sure about, I then decided to swap the Z15 2732 back to the GTB-OEM one I pulled out. The board woke up! Enough for me to probe all lines for a bit! "OK, is the specific U4 / Z15 combo some weird issue...? Let's put my "new" RIOT back in U4": it booted again! Let's put my board-pull 7232 back into Z15: Booted again... now 3 times in a row!

So I hooked up my old Heathkit 4550 analog O-scope to the IRQ line and turned on the board again: signal came up cleanly (a little noisy on the highs, but very clear and consistent pattern), and stayed consistent / steady / clean while I adjusted the scope. And stayed while I killed two more hours in the shop waiting for it (and me) to crash. Finally I turned off the scope and went to bed, leaving the board running on the bench: board was still running when I finally checked, 12+ hours later!

Power-cycled at the bench several times, it still booted. I moved it to the game, and it booted! Displays, and enough stuff to begin meaningfully troubleshooting the rest of the game!

Now I'm not holding my breath that it's somehow "fixed" especially since I don't know for certain what the last change was that got it to boot. Certainly, "swapping chips and moving things" can indicate a flaky trace or something, but I've since checked for those, swapped chips, moved the board around, and power-cycled several times now and even started a couple games (not that I can play given other issues) and it's at least reliable enough for me to cautiously proceed with the working on the rest of the game. So I'm calling this a win, for now. And hoping I didn't jinx it.

But the core issue(s) seem to have been dead RIOTS at U4 & U5, a bad 7404 at Z11, and/or bad 7232 at Z15.

System80... what an enigma...

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