Hello All:
Let me introduce myself as a pinball lover who after years and years of yearning for my own machine I finally found one and bought it! I am an electrical engineer who repaired pinball machines in my high school and college days while working in a TV Repair shop in the 1970s. (Yes, there was such a thing as TV repair back in the day).
I bought a semi restored Williams System 11 High Speed machine several months ago. The machine playfield was restored and clear-coated, LED conversions, and flipper/bumper rebuilds. The batteries have been relocated and the PCBs look good.
We have played the heck out of this machine and really enjoy it!
My problem is an occasional hang up. It seems somewhere between 30 and 32 plays (I am an engineer and kept a datalog), the machine will hang. The hang up symptom is flippers work, and music continues to play, but the following is random when it hangs:
1) Score segments may, or may not be lit.
2) A buzzing distortion may, or may not mix with the music.
3) TILT may, or may not register.
The only way to recover is unplug the machine.
My wife thinks that hitting the red/green/yellow switches on the left mid field cause the symptom, but I removed the glass and actuated these hundreds of times and could not get a hang.
The only thing repeatable here is the 30 to 32 plays. Unplug the machine and re-boot, and you are good for another 30-32 plays.
Power supply voltages seem reasonable. That is about all I know to look for right now and could use some expert advice.
Thanks for the time and your replies. Have a nice day, Bill

Thanks for the warm welcome and replies. I suppose I could just substitute the 5V supply with one of my bench DC supplies and play the game >30 times? Any easy way to 'highjack' the 5V supply with an external bench supply?

My pinball friends are all recommending cleaning the harness contacts on the monster PCB in the backboard. I like DeOxIt and pipe cleaners to scrub pins, and other advice for this?

Thanks, and have a nice day, Bill

Well, I don't know if I made any progress, or not, but I sure changed things. So, on the CPU PCB I removed each connector from the header, wiped with DeOxIt, and flooded the connector with DeOxit. Put it all back together with my DMM monitoring the 5V.

Played 8 games, and the strangest thing happened; the machine hung and the score digits turned to random noise. Little segments randomly cycling, and the music was two songs on top of each other. The 5V seems steady at 5.12V.

So, my 30 to 32 game problem is now 8 games; no progress here.

Next I had my wife play the game while I wiggled the harness and tapped the PCBs with a plastic screwdriver handle. No hang ups. Played about 10, or 12 games, no hang ups.

Put it all back together (scoreglass, etc). Played 4 games, and the machine hung. This time no score readouts, no music, and the flippers only work.

So, I again power cycle, ask the wife to play games, and I push on PCBs and ICs. Nothing! No hang ups. Played probably 15 games, while I am pushing on PCBs. No hang ups.

Put it all back together (again) played and played and played. No hang ups.

So, PLAN B is to remove the CPU PCB this weekend and look at soldering under the microscope.

Any other advice, comments, or opinions are appreciated. Thanks and have a nice day, Bill

Thanks, Grumpy. I'll blow the dust off my scope tonight and measure the 5V line.

Okay, some updates. Ripple was around 100mVp-p, which I thought was high. I pulled out the PWR SUPPLY PCB, and whether this is my problem, or not, this PCB needs some TLC!
Whoever repaired this PCB the solder job is NOT GOOD. Blobs and cold solder on some header pins, gooey flux and crusty flux covering many pins. The 18000uF cap seems to have leaked some electrolyte as the lead into the cap has white powder.
Like I said, whether or not this fixes my problem, this PCB needs some work anyway. All electrolytic caps will be replaced, and I will clean up the solder blobs and cold solder. I have a MetCal solder system (RF powered) and assembly microscope at work, so I'll stay late and do the solder clean up. Ordered caps form Great Plains with values as close as I could match in stock.
I'll update you when repairs are finished. Glad I found you guys. Take care, Bill

BTW, back in ye ol'TV repair days we would call this type of solder workmanship 'hat tracks'. HAT was our acronym for 'half a#s technician'. I pulled some cold solder off the pins with just a pull of my fingernail. Hopefully I have found the fix, but regardless, this needs to be corrected. Take care all, Bill

Okay, all new electrolytic caps and reflowed every solder joint I could find. Used no clean flux, but washed the PCB down with denatured alcohol, and of course DeOxIt coated and scrubbed the header pins.

Cross your fingers. I'll update tonight.

Well, I did not fix the machine. The lock up is not only random now, but different types of lock up:
1) No score display, no music, flippers work. No tilt. MCU 7 segment display "8".
2) Score and music, flippers and bumpers work, no score updates. Ball return not recognized. MCU 7 segment display "0".
3) See photo attached. No flippers, no music, lights in playfield not flashing. MCU 7 segment didplay "0".
Any advice, suggestion, or sympathy appreciated.
Take care, Bill

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Do you have a opinion on a new mcu pcb from pinballpcb.com?

No battery leakage evidence that I can tell.
Maybe I got lucky here. I decided to do another visual inspection of the playfield diodes, especially where the flippers has 'H A T' tracks. So, one of the flippers looks like a 3 year old soldered the wires, and I took my fingernail to insure the diodes were soldered/connected. When I did, this fell off the flipper (see picture attached). lead broken at cathode, AND cold solder on the anode lead!
So, maybe the theory of open diodes allowing back EMF into the MCU is indeed a problem? Unfortunately, no diodes in the house (used up my stock restoring an old Trans Oceanic for a friend). Fortunately, I have lots and lots of 1N4007 as work. Maybe good news to upadte you tomorrow night?
Thanks again for the advice.

20160309_193955_(resized).jpg

Frustrating!
Replaced two coil diodes. Took needle nose pliers and mechanical inspected all diodes under playfield. Played machine over two hours and stressed it pretty good with several scores over 3 million, and was proud of myself-no hang-called it fixed. Then it hung; different symptom now , the score for player two had a blinding bright single "2", so bright I unplugged the machine immediately thinking I would burn out the display. Also, this time no flippers, no playfield lights, and no sound. Power on reset, played a few games, then hung again same thing. Called it a night.
Frustrated right now; maybe time to throw in the towel and buy the $445 mcu pcb.....................

Thanks for the encouragement. Not sure what my next step should be? I do know that I need to go through and clean up poor workmanship, so maybe I need to spend a few hours looking the MCU PCB under the microscope?

Any other suggestions on the next step would be appreciated!

Have a nice day, Bill

I know I keep flip flopping around, but I am now fairly convinced I have a solder, or connection issue. My wife started playing the machine today around 3PM. Played for an hour-no hang. Left the machine on. I came home from work and played for about an hour-no hang. Ate dinner, a few chore, and played the machine for two hours, and yep, no hang.

Gotta be a fractured solder joint, or more poor workmanship on the MCU PCB.

I do not think I have a component failure.

Time will tell. More updates as I continue to dig around and play the game.

Have a nice weekend.

Came home from work tonight and decided to play a few games. Turned on the machine and KNOCK KNOCK KNOCK KNOCK KNOCK!!! Adjust Switch 52.
What!!!???!!!
Okay, so I did around on the internet, and it seems switch 52 has not been actuated in awhile. I find that switch 52 is the upper far most right rollover star. Take glass off, start game and sure enough-this switch does not work.
Long story short, blasted with DeOxIt. Actuated the switch 10 times and it registered.
Played 5 games and no hang up. Decided to quit while I was ahead.
More as this progresses.
Have a nice day, Bill

Okay, made the rectifier fuse upgrade tonight. Funny story; went to pull on the AC spade, and could not budge it. Grabbed the needle nose pliers, and still no budge. Could not even rock the spade side to side??!!??
Then I saw an oh so tiny solder spot. Whomever was in the this machine, they soldered the spade to all four terminals of the bridge rectifiers??!!??
Is this a common practice?
Can't find 8A slow blow fuses in the city of Tucson. Bought ceramic 8A high temp fuses.
See picture of completed upgrade. Still no hang, but only played four games to check functionality.
The 'five knocks' has not come back, either.
Have a nice day, Bill

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Why was this moved to the alpha numeric forum?

Just a quick follow up; it seems that I can almost predict when it will hang. The music will have some slight issue; either it will play slow, or the music will not end when it is supposed to, or songs might over lap.

Not sure if this could be a clue, or not.

Having said that, the frequency of hang up events is livable. Generally you can do < 50 games without a hang. I'll dig into the MCU someday soon at minimum a visual inspection of the solder.

I do appreciate any comments, opinions, or advice. Have a nice day, Bill

Thanks for the feedback.

The Power Supply has all new caps. I did observe that 5V ripple went from 100mVp-p to none, so it was an improvement there.

Since I have been in the electronics field over 30 years, at minimum I want to see if I can repair the MCU PCB. I'll visual inspect and reflow, and maybe replace the darlington transistors with improved versions, or MOSFET upgrades.

Then I'll throw in the towel and send the MCU off, but got to give it a try myself first.

Take care, Bill

Just a few updates. The machine probably has over 100 games played, and no hang up to date. Four of us played the machine non stop last Saturday for over two hours, and no hang.

However, it does 'try' to hang. Occasionally, the music will slow, or studder. One observer noted that the score updates are slow, also.

Still no real work to the MCU PCB. "If it ain't broke don't fix it", so I'm still going to wait as I am undecided on repairing the MCU PCB myself, sending it off, or buying a new updated PCB.

I've learned so much form this forum and thank you all for the time and help.

I'll update if any new progress, or problems arise.

Have a nice day.