Williams SS Black Knight (Williams, 1980) - Game works fine for several games and then credit button stops working

[Rusty]

@pinballdaveh
I purchased Black Knight 1980 Pinball Machine from someone that let me know that it works when it wants to.
That should have been my first warning but purchased it anyway. I did some research and after adjusting the
switches and adding 3 balls to game I was able to play a game. After playing a few games the machine would
start making weird noises and lock up.

I took all boards CPU/Driver and Power Boards to have them professionally serviced and hoped that would address all the issues.
After installing the serviced boards I am able to play 2 or 3 games and then credit button no longer works. When the machine is working
one of the digits in the player 1 score likes to act up but pushing one of the top connector on CPU board fixes issue for a while.
I did re-pin connectors on top of CPU board but still getting same issue. I plan on asking the tech to re-solder top connectors on
CPU board that feed the score displays to ensure they are making a solid connection.
After playing `several games I can add a credit but can't start a game by hitting the credit button.
I turn off machine for 15 minutes and then I can play a game again.

Issue also occurs if I just turn on machine and let it sit for 30 minutes or so, everything looks fine, I can add a credit but credit button does not start
a game after machine has been on for a while. Seems like issue is a function of machine being on for a while. I am bringing boards back to be serviced
again but am clueless on this one. Code on CPU board is 0 with coin door closed. Displays, Lights, Sounds, Switches and Solenoids test out fine using the test
mode in the coin box.

Have you ever run into an issue like this before??? Hoping to have some ideas of possible causes before taking boards back to be serviced for a 2nd time.
I see lots of people solving issues by replacing the connectors between the CPU and Driver boards. Tech claimed that was not necessary when he serviced the
boards the first time.

 

[pinhead1]

BK is over 40yr old machine.
who knows what the previous owners did to it.
i would look around for the easy stuff first.
maybe the power supply, something in the electronics is overheating and maybe a bad ground.
did you test the power supply and relays and look for bad wires?
check the power cord from the wall.
make sure its good and has a good power and ground at the PS.
can you lift the PF after playing for awhile and feel around the PowerSupply, relays etc...for anything getting hot.
check the voltage at the wall then again at the PS with a voltage meter.
find out what kind of PS cord it came with.
make sure the power cord from the wall is at a minimum a 12g.

i kind of had the same problem with my car a few months ago.
sometimes it would start and run ok for a little while then it would start bucking and stalling then clear up for awhile then repeat.
something in the dashboard was clicking away while it was bucking.
the clicking was the open circuit relay for the EFI.
turns out it had a bad 12gauge ground wire in the wire harness at the engine block.

 

[Rusty]

Thank You for the list of things to follow up on. Really appreciate the input! Will let you know if I find anything unusual.

 

[pinhead1]

Thank You for the list of things to follow up on. Really appreciate the input! Will let you know if I find anything unusual.

one more very important i left out.
it's been super hot everywhere.
everybody is using their AC, fans, swampers coolers during the peak hours.
this puts a tremendous draw at the transformer on the pole at peak hours.
i'm pretty sure voltage will drop during peak hours demand.
do a voltage check at peak hours in the wall plugs then later in the evening after it cools down when demand drops.
try BK later in the evening when it cools down when demand for power drops and see what happens.

 

[Rusty]

Went through list you provided and no luck. Everything checks out and have several other machines with no issues. I replaced the rectifier board and also the power supply to see if that resolved the issue but no luck. At this point feel there is still some issue with the CPU/Driver Board that starts acting up over time. Can turn on machine and play 1 game (let balls drain quickly) and come back in 30 minutes and everything looks great including taunting speech saying, 'Black Knight will play you' and it certainly has. Unable to start new game. Can add credits. Go into test mode everything checks out. Displays, Sound, Lights, Switches and Solenoids. Are there any components in the CPU/Driver Board that can work for a while and then stop working? Maybe something is loose (resister, capacitor, diode) or chips put in backwards? Bringing all boards back to Lenny's Pinball Services for 2nd time in Plainfield so hopefully he can find the issue if it is in the boards.

 

[Isaac Sauvage]

@Rusty,
The way features drop in and out after a period of time does remind me of stuff like cold solder joints and failing caps.

I've never worked on a SS myself, but you might want to take a look at the guides linked HERE. For example, there are specific resources for BK, as well as a general resource for repairing System-7 games, of which BK is one:

http://www.pinrepair.com/sys37/manuals/wms7-blackknight-op.pdf
http://www.pinrepair.com/sys37/index1.htm

 

[pinhead1]

Went through list you provided and no luck. Everything checks out and have several other machines with no issues. I replaced the rectifier board and also the power supply to see if that resolved the issue but no luck. At this point feel there is still some issue with the CPU/Driver Board that starts acting up over time. Can turn on machine and play 1 game (let balls drain quickly) and come back in 30 minutes and everything looks great including taunting speech saying, 'Black Knight will play you' and it certainly has. Unable to start new game. Can add credits. Go into test mode everything checks out. Displays, Sound, Lights, Switches and Solenoids. Are there any components in the CPU/Driver Board that can work for a while and then stop working? Maybe something is loose (resister, capacitor, diode) or chips put in backwards? Bringing all boards back to Lenny's Pinball Services for 2nd time in Plainfield so hopefully he can find the issue if it is in the boards.

sorry, i don't have anymore ideas.
checking the power cord, connections, wires, PS, overheating components, low voltage at the wall plugs at peak hours was an easy no cost attempt to find something.
what was the voltage at the wall plugs at the hot peak hours??

 

[Rusty]

using multimeter AC Voltage on wall plug it shows 120.1 so voltage is OK. New development on machine now. Machine will not start to play a game but displays code 04 in player 1 and also in credit / match area. Whatever issue was, machine is no longer playable so maybe it will be easier to identify issue by tech when I bring boards in again. Tried turning machine on and off in succession quickly but will not start up correctly. Thanks for ideas. I will give update once tech works on boards again and hopefully provide some useful information if anyone else has this issue.

 

[pinhead1]

using multimeter AC Voltage on wall plug it shows 120.1 so voltage is OK. New development on machine now. Machine will not start to play a game but displays code 04 in player 1 and also in credit / match area. Whatever issue was, machine is no longer playable so maybe it will be easier to identify issue by tech when I bring boards in again. Tried turning machine on and off in succession quickly but will not start up correctly. Thanks for ideas. I will give update once tech works on boards again and hopefully provide some useful information if anyone else has this issue.

>>>>using multimeter AC Voltage on wall plug it shows 120.1 so voltage is OK.<<<<
120.1 is good at the wall. was that at peak hot hours of the day or night when demand dropped?
what was the voltage at the other end of the cord at the PS in the machine?...