Gottlieb System 1 CPU board DEAD – advice needed on where to look

[JRK1971]

Ok I’m reaching for help now guys. 

I’ve cleaned all the acid damage from my Countdown MPU board and it still not booting up (replaced Z9, Z8, Z28, Z6, Z7 and all the resistors and caps around them). All I get is the shoot again light on, and no score displays (1 out of 5 times they might show up after 5 seconds), but the machine doesn’t play.
The machine plays fine with my Niwumpf board, so I know all power, and other boards etc are good.

I’ve grabbed the CRO and can see that:
The reset cct works
I have a clock signal
I’ve got signals at TC1 pins 1-10ish, above that, they seem to be high (5v)

I’ve got sockets on U3, U4, U5, so I tried spares (not sure they are 100%, I did match U4 & 5 per guides), but got exactly the same fault so im thinking it can’t be them (surely fault would have changed even with a faulty replacement).
The only CPU/ spider chips I haven’t tried are U1, U2, U6.
Im wondering if Z30 “4-16 data strobe generator” could be faulty, but don’t see why this would hold the machine from booting correctly as its not tied to the address or data bus.

Any advice would be greatly appreciated.
Wondering if anybody has any advice on where to look next?

[Retropin]

First up.. GTB sys1 games are pretty much an attempt by GTB to enter the SS new generation system. They got it very wrong compared to what we know today.. given that, its the same logic that got man to the moon in 69 and knowing what we now know, its a miracle they got back!
Biggest weak link of any sys 1 game is that as soon as any coil locks on, the associated IC would have fried also.. the current backwash just goes straight up the line and kills the IC. If this has happened then your CPU is pretty much dead as the spider chips are obsolete and have been for some time. You see sys1 CPU boards for sale often on Ebay.. listed as untested which is BS.. it means they don't work and will not work.
test ALL your spider chips..  a simple visual test that any that have burn marks in them means your CPU is dead and you need a replacement.. don't even bother going any further.
 If you do get it going then put diodes in line to stop the current switch off trailing backwards

[beaky]

First up.. GTB sys1 games are pretty much an attempt by GTB to enter the SS new generation system. They got it very wrong compared to what we know today.. given that, its the same logic that got man to the moon in 69 and knowing what we now know, its a miracle they got back!
Biggest weak link of any sys 1 game is that as soon as any coil locks on, the associated IC would have fried also.. the current backwash just goes straight up the line and kills the IC. If this has happened then your CPU is pretty much dead as the spider chips are obsolete and have been for some time. You see sys1 CPU boards for sale often on Ebay.. listed as untested which is BS.. it means they don't work and will not work.
test ALL your spider chips..  a simple visual test that any that have burn marks in them means your CPU is dead and you need a replacement.. don't even bother going any further.
 If you do get it going then put diodes in line to stop the current switch off trailing backwards

totally agree
once a spider chip is dead then kiss it goodbye.
even if the the switch matrix spider chip fails (hope i have labeled it correctly) then your board is cactus
 
 

[JRK1971]

Thanks guys for the advice.

I was hoping somebody has used a CRO and gone a bit further/ might have some more detailed problem solving advice for the system1 board.

I've used the Pinrepair guide but he stops at checking the data & address bus by saying if you have no data/address signals, game over. I was hoping to go a little more in depth and try and fix. It appears as though potentially one of the spiders is holding the data or address bus down, but im flying blind as I have no info to go on.

I realise Im wasting a heap of time, but I'd rather keep the orig board going.

[Strangeways]

SYS1 CPU boards are simple fixes. If the spider chips are dead, throw the board in the bin and buy a Pascal or Ni-Wumpf. I'd rather spend time repinning the connectors for a new board than fixing the old one. It is a ticking time bomb anyway (spider chips).

[Retropin]

Thanks guys for the advice.

I was hoping somebody has used a CRO and gone a bit further/ might have some more detailed problem solving advice for the system1 board.

I've used the Pinrepair guide but he stops at checking the data & address bus by saying if you have no data/address signals, game over. I was hoping to go a little more in depth and try and fix. It appears as though potentially one of the spiders is holding the data or address bus down, but im flying blind as I have no info to go on.

I realise Im wasting a heap of time, but I'd rather keep the orig board going.

You can check the data bus with a logic probe, or attach a CRO, but Clay is saying what we are saying here... if you have nothing then the spider chip has failed and the board is a throw away

[JRK1971]

Sorry guys,
First of all - thanks for all your advice. 

What im saying badly here is...

I've got 3 spare System1 processor boards with parts (spider chips etc), plus some already removed spider chips (U3 U4, U5).

I've got a CRO

I've got a  Niwumpf board and the game plays fine with it.

I just wanted to try and resurrect the dead orig System1 CPU board.

I realize it will probably die again, but I've put machine sockets in almost all the spider chip locations so changing is getting easier.

I was just hoping somebody had investigated a bit further along the data & address bus side so I could gleam some advice (Im guessing one of the spider chips is holding down half of the address bus, but I still have U1, U2, U6 hard soldered to the board, so removal will take alot of time, hence the q..

I've already wasted a heap of hours on the System 1 board so I don't really want to give up.

Apologies if it seems like Im stuck on a point here, just trying to clear up where Im at and why im still trying to go down the road less travelled   

[dazza]

Don`t know if this is any help ?
http://home.scarlet.be/~nb010944/syscpu/esyscpu.htm

This is the main site.
http://home.scarlet.be/~leonb1/eindex.html

My pinball pool is now operational.
Also done the earth and circuit board leds mod.

[Boots]

Have you tried the other original boards you have yet?

[JRK1971]

Ok just to prove Im dumber than I look, I've spent the last 3 hours in the shed looking over this board again. Im trying to send myself insane working on a system1 board

I've got the board working again - but only when I run it from a PC power supply, It doesn't boot when using the Gottlieb power supply. Interestingly if I use the PC power supply for +5V and -12V and the gottlieb power supply for 42, 60v the machine boots fine (im making sure I have a common ground between the two power supplies).

TO make things even stranger, the PC power supply is only outputting about -11VDC, not 12V DC...

This is very strange as the Niwumpf board plays fine.

This has me wondering if I have either
1) problem with -12v rail on gottlieb power supply (Niwumpf doesn't use it)
2) enough mains noise to effect the System1 board, but not the Niwumpf
3) potentially have a startup issue with the system 1 with the games power supply not being stable when the reset goes high.

The mains noise on the Gottlieb supply is in the order of 0.05V on both 5V & -12V rail (measured with CRO). Bloody stuff all.

Im scratching my head now, can't let this go... Thinking I might throw some electrolytic caps at the Gottlieb supply.

Guess the good point is the System1 board is up and running again (well with a PC supply).

Anybody seen weird stuff like this before? Any advice...

Time to turn off the brain and go to sleep

[Mr Pinbologist]

With the system 1 MPU if the -12v rail goes down usually the tell tale sign is that all the coils instantly lock on when the game is powered up.

[Homepin]

The replacement boards are built using modern technology - the originals were a VERY poor design right from day one - the faults and problems were simply poor design and no amount of 'repairs' will fix that.

Even if you were lucky enough to get it working it would be unreliable and probably take out other things - these machines did this from BRAND NEW.....I was in the industry unboxing these readying them for site and all the technicians would cringe when a new delivery of these monstrosities was delivered because we knew what headaches and fights with site owners were coming.

Trust me, throw that board away - better still, cut it in half so nobody else wastes any more time on it!!!!

The replacements are far more tolerant to voltage fluctuations etc. which would explain why they work and the original is just rubbish!

[Boots]

Ok just to prove Im dumber than I look, I've spent the last 3 hours in the shed looking over this board again. Im trying to send myself insane working on a system1 board

I've got the board working again - but only when I run it from a PC power supply, It doesn't boot when using the Gottlieb power supply. Interestingly if I use the PC power supply for +5V and -12V and the gottlieb power supply for 42, 60v the machine boots fine (im making sure I have a common ground between the two power supplies).

TO make things even stranger, the PC power supply is only outputting about -11VDC, not 12V DC...

This is very strange as the Niwumpf board plays fine.

This has me wondering if I have either
1) problem with -12v rail on gottlieb power supply (Niwumpf doesn't use it)
2) enough mains noise to effect the System1 board, but not the Niwumpf
3) potentially have a startup issue with the system 1 with the games power supply not being stable when the reset goes high.

The mains noise on the Gottlieb supply is in the order of 0.05V on both 5V & -12V rail (measured with CRO). Bloody stuff all.

Im scratching my head now, can't let this go... Thinking I might throw some electrolytic caps at the Gottlieb supply.

Guess the good point is the System1 board is up and running again (well with a PC supply).

Anybody seen weird stuff like this before? Any advice...

Time to turn off the brain and go to sleep

Have you rebuilt the power supply?
The Niwumpf may be more tolerant of a crappy power supply than the original board.

[JRK1971]

Thanks guys, appreciate all the advice and horror stories 

It would of been fun days back in the late 70's rolloing the machines. Homepin - did you collect a heap of pinnies in the early 80's when they went out of fashion? Wish I was old enough to have bought up big back then

I was pretty surprised that the Niwumpf worked with the orig supply. More so I am wondering now if my orig PS is heading to the exit. I rebuilt the Power Supply in the early 90's, and its been played stuff all. Spent most of its time in the corner of the garage. But as im sure you guys will tell me, electrolytic paste dries up so I'll pull the Power Supply down and replace all the electrolytics.

Im taking a guestimate that even the Niwumpf will stop working in time as the PS gets worse. Funny thing is the noise is jack sh!t on the rails, im wondering if its worse at power on and given im using a non-storage CRO, I will never see it.

Apologies if my rambling is taking up too much space and time on here, Im like a dog with a bone, can't let it go until somebody distracts me.


Where you you guys buy electrolytics from? eBay?

[Homepin]

caps from Jaycar