Hey guys, working on my black knight.
This has been a year long project, clear coated pf, complete tear down and rebuild.

Recently, I was blowing the solenoid fuse, and I couldn't find the culprit, so I decided it was time to replace the 40 pin connector, the male and female, I checked my work on top and bottom, every pin gets continuity with the next point on the pcb

Now the bottom left target solenoid is locked on.

I check the wiring, Nothing crossed or grounded. the corresponding transistor is not shorted, the coil ohms at 2.7 ohms

Any ideas on what to check from here?

Thank you gentlemen, I'll report back

I replaced all 3, still locking. (Confirmed correct transistor and pre driver)

To test, and isolate , I removed the driver wire (gray - red stripe) and placed that wire on another drop target coil (after removing the other drop target coils driver wire) , then power on, this coil locks also. Removed wire, replaced original wire, the coil functions properly

Thank you

Thank you here too, I was about to drown myself in the schematics, I hate how this pcb is not labeled, I'm terrible with schematics

I replaced the 7408, 14 pin chip and the problem persists.

Only one them of them is socketed :/
Guess I could replace the PIA while I'm at it

will this work? Thanks for your help vid!

ebay.com link: EF68B21P Peripheral Interface Adapter PIA DIP40

Anyone else know if the ebay link to that PIA will work?
Bump

hehe, nevermind, found them at Jameco for a little less

I replaced the 6821 PIA and socketed it and The coil is still locking on.

Please help, I'm at my wits end

Thank you

I have a logic probe, but I'd need a way to see what to follow.

I guess it's possible, I'll have to do a thorough investigation, I always check all of my work, if I dropped solder somewhere and bridged a connection, it's somewhere else on the board, not the pins, they were proper

TP9 = hi

IC1
Pin11 low
12 low
13 hi

your better at this than I am I'll look as soon as I get home, thank you for diving in!

Ic1 pin6 low
5 high
4 low

Cody, I'm so sorry I missed this post somehow, I'll check Monday when I'm back with my game

On a side note, I replaced the coil, didn't help, I really didn't expect it to lol

The first thing I did when I discovered the issue was replace Q16, and Q17, maybe one of them could still be bad?

Finally I'm back , sorry for the long absence...

Q16 left low

Q16 middle low

Q16 right low

Q18 left high
Q18 middle low
Q18 right low

All of the Q's are acting normally except q16 and q17, and r33

The top of r33 is normal when compared to the rest of the corresponding r's

But the bottom of r33 is abnormal to the rest of the bottom of the corresponding r's

68 ohms is correct, all 3 are at 67.4

Probing :
R33 top high
Bottom low

R36 top high
Bottom high

R39 top high
Bottom high

image.jpg

So, I replaced it again, same thing... I ordered 2n 4401's from Marco a while back... But they sent 2n5401's

So that's what I'm using... I don't know if that's a good thing or not

I dug through my parts and found A 4401 , put it in.....

And...

It works!!!!!!!!

Thank you thank you thank you Cody!