I am trying to track down a switch matrix issue on a JD, before I burn it as firewood!

Having researched switch matrix issues, I have managed to draw a rectangle around the ‘rouge’ switches and I think it’s a diode issue, but tracking it down has been thus far been impossible.

What is happening; is when SW18 3 Bank Targets is hit it also activates the SW14 Tilt-bob, also when the SW38 Subway Enter 2 is activated it triggers the SW34 Inside Right Return. Thus making the rectangle on the matrix.

So I have replaced a diode on the first of the three SW18 3 Bank Targets (others tested fine so did not do these), the diode on SW34 Inside Right Return & SW38 Subway Enter 2.
All of the diodes taken out tested fine, so they clearly were not the issue.

Looking over other switches all diodes look to be on the correct way round, added to this I have tested a number in place and the appear fine.

I have put in a known working coin door interface to eliminate the tilt diode and other coin door and front buttons.

SW58 Drop Target ‘E’ is flaky as it flickers on and off, so I plan to reflow the solder. But I did simply disconnect the connector to that board and still had the switch problem.

Some switches in column 1 and row 4 are optos, do these have diodes if so where and how do I test them?

Any other suggestions as to what to do, test or how to work through this issue, its driving me mad!

Cheers

Julian

jd_(resized).jpg

Still stumped on this problem.

I have disconnected the switches going into the MPU and made the connections using a jump wire and the 'faulty' ones work just fine so its not the MPU, here is an image with the connectors off;

IMG_20160719_174411_(resized).jpg

Here is the issue with one of the two faulty switches, you can see the lower left matrix switch come on the 3 bank target and the tilt-bob half way up on the same column.

During some more fault finding, I used the multimeter in diode / continuity test to see if the row wires were good between switches in row 4 (white & Yellow).

What I found was strange as I would have thought I should get full continuity on the white & yellow wire on all switches and molex connectors going into opto boards and JUDGE opto board in that row, most I did but a few I got .516 which would indicate a diode reading!

Does this indicate a green & white wire on a switch in that row is connected wrongly?

OK a further update;

If I disconnected the J1 connector on the coin interface board and the switch errors do not happen, but plug it back in and I get the two switches firing.

I've tried to narrow it down further with no luck, as disconnecting the other coin interface connectors one-by-one leaving J1 connected the error still happens, so I dont think its a front or side cabinet switch issue like fire, start or supergame.

One thing I did notice is if I plug in J1 from the bottom of the connector so only the lower pins make connection the fault does not happen until almost the last 1 or 2 (top) pins are connected and this is where I notice switch 25 (always closed) kicks in and its when this switch is active I get the issue.

Again I have tried another coin door board and still get the same issue.

All points to this now but I've taken a working one from another JD and get the same issue.

What is switch 24 for? This is in the same row as the 2 erroneous switches that are being triggered.

Any suggestions?

Photo of 3 bank target.

IMG_20160722_210149_(resized).jpg

Sorted!

I posted the issue on a UK pinball forum (www.pinballinfo.co.uk), and a chap said he had had exactly the same issue a while back and it turned out to be 2 molex connectors under the playfield near the deadworld (so lower left) that were incorrectly connected (i.e. swapped over).

http://www.pinballinfo.com/community/threads/judge-dredd-2-switches-firing-at-the-same-time.33824/

You will see in the photo the 2 molex that were plugged into the wrong connectors, simply swapping over these 2 and the switch matrix is fully working.

IMG_20160722_070346_(resized).jpg

The machine was 'new' to me and came with this issue.

Just glad someone else had the exact same issue so knew what the problem was, as it would have taken a while to track it down otherwise.

Apparently its common on Judge Dredd as working on Dead World means when its put back together its easy to get these 2 swapped over.

Updating so others may be able to find the solution if they get a machine with this issue.