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Space Jam lamp matrix issue

B

BobWood

Registered
Joined
Aug 21, 2019
Messages
82
Location
Neyland, Pembrokeshire
Hello, first of all, let me explain that I'm new to this pinball ownership stuff, so excuse me if I ask dumb questions or don't use correct terminology.. That said, here's my problem and what I've done so far.

I've had the machine for just over a week and it is playing very well, I have replaced a few blown lamps and given the play field a bit of a spring clean. Now the initial rush of playing the game is subsiding, I'm starting to take more notice of what is lit on the play field and it seem to be wildly optimistic on the bonuses and achievements so I decided to do some testing. Sure enough, when I go to diagnostics and do a single lamp test 5 lamps light. I scroll through all 8 columns and the same rows light in each case 1, 2, 4, 7 & 8.

I have had a trawl online and found something similar but their fixes (there were multiple instances of similar behaviour) ranged from checking each lamp diode hadn't been pressed to make contact with the lamp casing, through reseating the ribbon cable between MPU and CPU (I reseated any ribbon cable I could see and all other connectors just to make sure), the ultimate fix seemed to be have the board sent away and repaired.

My question is, is there a documented methodology for checking out lamp matrix issues, if so, does anyone have a link? Failing that, does anyone have any pointers I could follow?

Grateful for any pointers, it is not spoiling my enjoyment of the machine but, I've found, if you don't attend to issues as the appear, they tend to mount up and bite big time.

Regards
Bob
 
Not sure if I’ve understood your problem entirely, but this might help.

The way I do this is to check each connection to the row circuitry.

Put the machine into all lamp test. Remove the row connector from the circuit board. Touch position one of the connector against its normal pin. Pin one.

You should see the correct group of lamps flash on and off. (Unless this is the defective row, in which case they won’t turn off ). Move that position one on the connector along the pins, the same group of lamps will flash on and off. If the pcb is good, all lamps in the group will clearly flash on and off. If a row does not turn off correctly then you have identified that the fault is on the board.

This method can also be used to check the columns.
 
Well, I've had a go and get the following
Pin 1 on the board dabbed onto each connector on the row plug - each one looked good - so problem is likely on the board
I then dabbed each pin on he board to pin 1 on the row plug - this time I got mixed results
1, 2, 4, 7 and 8 were very bright while 3, 5, 9 and 10 were dimmer.
Did the same exercise on the column side and all appears OK
So, the issue is on the board, it is either the 4 dimmer ones or the 5 brighter ones (given the 5 brighter ones correspond the rows with issues would it be right to suspect these? )
Is it likely to be he transistors on the rows or could the issue be further inboard, if so, how to proceed?
 
I took the board off and checked out the transistors, appears that I have 5 bad on the row side . As I said before, it is not having a big impact on playing so there's no urgency. Manual says they are STP19N10L,, obsolete but I should be able to find equivalents. Then it will just be a matter of "will I have a go or will I buy some expertise in?" Time to dust off the soldering iron....
 
Well, it took a while to get some bits together,. Have swapped the suspect MOSFETs (the testing I did whilst they were in circuit were probably not valid but they were useful in a comparative way - rows that were working gave different test results to the ones that were). So, having swapped them the situation is much improved. Not perfect, but much better than it was.
Now the correct lamp lights and, in a few cases, secondary lamps glow very dimly. I think that the issue now may be external to the I/o board.
It is getting there....
 
Do you have normal incandescent lamps or do you have led lamps installed. Leds will produce the symptoms you see.
 
They are LEDs in the main.
As it stands right now, I'm quite happy with the way it works, the 'dim echoes' don't show up in normal play only in diagnostics.
I think I can call this a fix for now and move on.
To the next issue, problem, niggle, 'I thought I might try'.....
 
I'd like to thank pinballmania for the pointers (I've only been retired a few years but it is amazing how quickly you forget the basics of troubleshooting. Problem with a link, split it and check if problem is upstream or downstream . In this case, a connector is a perfect place to do this).
Thanks again pinballmania
Regards
Bob
 
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