Just helping a friend with his Black Knight. All switches on row 7 of switch matrix are not working, and report as closed in switch test. I've checked all involved switches for shorts, loose wires/diodes etc. and all seems good. I know it's always said that you need to disconnect one end of the switch diode to get a proper reading on it, and I only had time to do that with one diode before I had to leave and it tested fine. Now, I tested all the other diodes without disconnecting one end and they tested fine this way too, so is it absolutely crucial that I disconnect one end? Will I get false readings if I don't? I pulled his CPU and driver boards to bring them home and re-solder all the connector pins in the meantime, and check the resistors etc associated with the rows, all seems good there. I live 3 hours from his place but I'm going back in a week so I'm hoping I can resolve this issue for him next time around. Thanks for any help!

Thanks Terry, he does have LED's installed but I'm not sure if the power was on or not, I wouldn't think so but definitely will check. I've never heard of this happening before so thanks, I will check that next week and see what happens. Which components would be blown if that was the case? IC16, 4049? Maybe the PIA IC11 6821?

The resistors were the first in line with row 7 and they're fine, and I tried to pull the little .01 capacitors and test them but got a 0.0 reading with my DMD set to 20k ohms, not sure how else to test them. I tried a couple of the other same type capacitors to see if my 0 reading was correct but they measured the same, 0. I know they can't all be bad because it's only row 7 giving me problems. Next in line I guess is the 6810 IC but before I go pulling it out to replace it I'll wait till I get back to the machine and do the jumper test between the row and columns. I wish I had a better way to test those wee capacitors, so if there is a way to do it properly with a DMM I'd love to hear it, thanks for all the help!

I just hope that touching up the solder on the connectors was actually the problem, but not holding my breath lol.

Thanks terryb, but I don't have one yet, it's on the list. I'll see if I can find one in town tomorrow but I'll likely have to order one in (small town woes).

Many thanks!

Sorry it took so long to get back with my results, so here is what happened.

I touched up the solder on the connector pins and tested the resistors in line with Row 7 switches, seemed fine.
I installed the boards back in the game, turned it on and removed 2J2 and 2J3 and went into switch test. All row 7 switches were still showing as activated even with connectors out.
I connected the connectors again and still the same thing, switches weren't working on Row 7.
I wiggled a few connectors, played with this and that, and I'm not sure what did it but suddenly the switches started working, all except for one of the drop target switches in Row 7.
I installed a new diode on the drop target switch and now it is working as well, so all switches now operational.

I don't know why, and I'm sure it'll fail again whatever it was, but it works for now. Could it have been that one diode all along? Could there be an intermittent problem with a chip on the board or something?

Thanks, I am going to change the switch connectors as soon as I have time to be certain they're not playing a part in this. The 40 pin connector has not been changed. I tried to separate the 40pin connector but it was so tight that I decided to leave it together rather than risk damaging anything in the process.
I did go over all the solder joints on the male pins too with new solder, including the 40 pin connector.

I'm just wondering why those switches in Row 7 still showed as being closed when the connectors weren't attached? Then miraculously started working again, not sure what I did to cause that if anything.

The chips aren't socketed and there is no battery damage at all, the board is clean. I will leave it as is for now and see how it goes, but sounds like new chips and sockets could be something to try if it fails again? Fingers are crossed Thanks again for the help!