Hi - so i picked up this board. It's been worked on before (lots). Long story short I have got it working after sorting out a few faults. Knackered Roms, A short under U8, rebuilt the Reset section. The board has been mainly re-socketed. U9,10,11,2,6,8 and what looks like a decent job done and all pin out ok.

So - got it running and thought that was it. Played some games and everything working as it should.

Then after about 15 to 25mins it tilted with that cocky too much English comment and re-booted. Fair enough. 25Mins later it just crashed. Keep in mind this is a fully working cabinet. I currently have two EBD Limited Editions so for sanity I moved the MPU to the other one and same results so cabinet issue is definitely out of the picture.

So once crashed - If you re-boot it starts up ok but repeats the above.

I noticed for some weird reason the controlled lamp sequence was running slower than standard. Did some scope measurements. Zero crossing 100Hz (UK 2x 50hZ) so spot on. Clocks 535Khz - ok (I think as a little lower than my others at around 580 to 600khz). Timer 450Hz...mmm about 130hz too fast. Checked and R21 had been replaced with a 23k. My 36ks are on order so I put 4x9k in series and the clock dropped to 310 which is pretty close and within tolerance and the lamps started going at the right speed.

Now I know the timer does the display interrupt and not the lamps but I'm thinking the processor was busy doing a lot of extra interrupts from the timer that everything else got a bit slower and I was convinced this was the crash problem and that will be it sorted.

Lamps running correctly yes but after 25min Tilt! 15 mins crash...

All signals seem fine and in range (then boom crash). So I have no idea how to search for this fault.... Ideas????

What affect would a 535Khz clock have compared to 580-600khz?

Just an update. My 535Khz clock. Did some fault finding and the previous guy had again put in a wrong value resistor. R7 should be 1K and he had 750 Ohm. So put in a 1K thinking job done Well the frequency dropped to 525Khz aaaarg lol Checked the rest of the components and swapped C14 & C15 as well and no change. Replaced U16 for the hell of it and it came back up to circa 535Khz... back to where I started but at least with the right R7...

Current non-overlapping clock signals...
Clocks (resized).jpg

Put back in for a test and after 22mins - reset alarm - auto reboot - back up and running in attract mode - but not fixed. Hate this type of fault. It should just break so you know it's fixed when you get it working. This infrequent type of glitch is a bitch to find...

There was corrosion. It took out a few tracks right by the battery but the rest was pretty good. I Jumped the tracks on the rear for reliability. Reset & Timer section hardly affected at all. I rebuilt most of the Reset anyway just for good practice. The board has been re-socketed before me and he's done a decent job (except for one faulty track under U10 which he has jumpered). I re-socketed his new U9 socket searching for the fault just to be sure.

Quench - swapped the PIA's around and with new ones multiple times. I also replaced the bypass caps on the Tilt line. I think it was C40 & C39 but no joy. I will do those measurements after the current test. I replaced the processor and running a test. So far running an hour without issue which looks positive (twice as long as normal) but too early to tell 100%. It was a gold 6800 Motorola chip which I've never seen before. I'm thinking maybe an original? Obviously still works but maybe failing under stress from age. Fingers crossed.

Barakandl - if this new 6800 also resets my next step is to replace the newer U10 socket myself and see what happens. Although it looks good and measures out 100% so probably fine.

Didnt tilt but crashed at 70 mins

With the J2 and J3 connectors removed from the MPU board what resistance do you measure on the MPU board between:
J2 pin 1 and pin 2 - 114.4k
J2 pin 2 and pin 3 - 114.4k
J2 Pin 3 and pin 4 - 114.8k
J2 pin 12 and pin 13 - 115.7k
J2 pin 13 and pin 14 - 114.9k
J2 pin 14 and pin 15 - 114.3k

Slam alarm if it re-boots OR it just crashes with only GI running. When it crashes all voltages are still good. It's during attract mode. Although I have only played a few games in a row so maybe if I played longer it may happen but so far attract mode.

At that desperate point where you start doing weird crap just to see what happens. Maybe I need to swap the U10 socket just too see
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They are the only U15's I have although I have an old one I took off a board I could try. Yes I have pressed banged and knocked and it does nothing. CR18 is ok - maybe just the pic.

Thanks for the link. Is Gate 4 U15D?

Ive put an original U15 in the socket. Testing...

12 mins - and it reset...

I'm out of ideas lol

Ive put one of the original U15 chips back in last night but it does the same...

I will test in game mode and feedback

Running in game mode for 2 hours now with no issues... so it's only in attract mode after about 25 Mins. So it must be current based but where?

Ive checked all the signals and they are basically the same. I suppose because the board works. When it glitches in attract mode it happens so quickly you don't get a chance to test anything.

The only difference in signals is that most of my boards have a clock speed of 575khz to 600hz whereas this one is 535khz but seemingly that is within spec. I have rebuilt that section anyway with no change in clock speed.

Something must have a bit of a current draw during attract mode to hang it up but nothing is getting warm. Its also strange that sometimes the effect is an alarm and reset whereas other times is just a straight hang up.

U14 - I ordered some UB's but the eejit sent me b's even though I specifically mentioned that in the order...

The scopes good. I have a seperate tone generator and the scope measure it spot on. I will take a look at the S&Q freq later though.

Newbie to eprom programming. I will take a look at that. That's interesting