I picked up a BK as a project pin a few weeks back. When I walk through the switch test it tells me that 39, 31, 23, 15, and 7 switches are closed. I looked it up and that is row 7 of the switch matrix. A quick Google search brought me to the PinWiki for Williams. Following those instructions I pulled J2 and J3 from the driver board. Even with the connectors out, every switch on row 7 is showing closed. I have a logic probe on it's way to me now, but I am thinking that 1 or both of the switch row IC's are fried. They have F4049BPC stamped on them. Can someone point me to a place where I can order replacements?

This should prove interesting as I am at the very early learning curve with my soldering skills.

Thank you very much! I see 2 versions of the chip are available. One indicates buffered and the other is unbuffered. I don't see anything on the chip or schematic that mentions which to use. I assume I have to use 1 type. Do you know which type I should get and, more importantly, how would I be able to get that information for myself in the future?

Digging a bit futher in the PinWiki, I found this:

Two 7406 (Hex Inverter / Buffer with open collector HV outputs) is used to 'drive' the Columns.
A 7406 or 74LS06 will work and are common parts.
Two 4049 (or 14049 "CMOS Hex Inverter / Buffer) is used to 'read' the Rows.
The MC14049 or CD4049UBCN are common examples, although any 14049 or 4049 14-leg DIP will work.

It looks like it is unbuffered. I haven't ordered yet, so I will have to post back when I get things installed and working.

Ok, new chips (and sockets) are on the way, but before I start surgery on the board I would like to verify the chips are bad.

I picked up a logic probe and I read through terryb post on using it. The PDF manual has the schematics and it took me a while to find what I was looking for. The schematic looked like the switch matrix was going directly into the PIA, but there is a hand written 4049 or 7406 at the beginning of the line. What it doesn't say is the input or output voltage. How can I tell which voltage to apply to hook up to the logic probe for input and output of the chips?

Thanks for the information. I found 5V and hit the 4 chips with the logic probe with the game in switch test mode, while writing down the results. When I tried to decipher what the data was telling me, I noticed that I had forgotten to reattach the switch columns and switch rows connector. Does this invalidate the probe results?

For reference, here are the results of the 2 4049 chips:

Upper Chip

Pin 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16
Result H L H H 0 L H L H L 0 H 0 H L 0

Lower Chip
Pin 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16
Result H L H L 0 L H L H L 0 H 0 H L 0

They are the same, with the exception of Pin4. Based on what I was reading, I was expecting these to be constantly pulsing. When it comes down to it though, I did not have the connectors attached, and I still do not know what I am doing.

Thanks, that makes total sense. I used a jumper on all the row inputs and traced the signals back to the chips. Row 7 traces to pin 7 on the lower 4049. When I jump the input pin, pin 6 on the 4049 goes hi. I assume that means the 4049 is working. I then traced pin 6 back to the PIA II and it traces to pin 3 on the PIA II. Jumping the input on row 7 will put pin 3 hi, which I assume is what it is supposed to do.

I have no idea if PIA pin 3 drives an output elsewhere on the chip. Does verifying that the signal is making it to the PIA imply the PIA is bad? I am not sure where to go from here.

Damnit, you are right! I did it backwards. Well at least I know row 2 works.

I'll get everything setup again and test row 7 next.

DOH!

Ok. I did the test again; correctly this time I hope. The trace back to the PIA seemed ok. When I tested the jumper, the signal would change as I expected. Row 7 traces back to pin 8 on the PIA. What was interesting is pin 8 was always high. I tested the trace where the socket met the board and the signal was low, but when I tested the pin on the chip, the signal was high. I am not sure how that happens.

Yes. The pin of the chip read high, but if I test where the socket goes into the board for that pin it reads low.

Ok, I took the chip out of the socket and used the DMM to test continuity. It does not look like the socket pin is in connection with the trace. The chip legs look fine. My concern is that the chip leg was reading a high. It is my understanding that these pins should be reading the input of the rows matrix. I would be expecting the pin to be either low or 0 signal, not high. If this pin is reading high, am I at risk of damaging the 4049 chip or anything else "upstream" of the PIA pin?

It looked like the socket for that pin was broken. With the chip out, I could look down and see the board. I have removed the socket, but have not yet put the new one in.

There was already a jumper from a missing trace. It looks like the one below it also fell off. This is still new to me, but is this what the board should look like after removing the socket?

36CF2274-3011-4ED0-940F-CBFA613507AC (resized).jpeg

9F49AA54-7F06-4A33-8CCC-F705B2BE9583 (resized).jpeg

They are 15 and 14, but on the back of the board.

Thanks for your help. This will take me a while so I will post back in a few days when I get through it all.

I put in a new socket and verified the traced were connected to the board. It took a few tries and it is not pretty, but the connections are made. When I replaced the PIA chip and went in to test mode, I got the exact same issue. Row 7 was showing closed. Just to verify if the circuit would work, I took a jumper and touched the pin from the 7049 to Pin 8 of the PIA directly. As soon as I did, the game stopped showing row 7 as closed. When I removed the jumper it would revert back to the incorrect behavior. I got someone to help and I then used the jumper, put the logic probe on the pin and also jumped the row input pin on the board. I have no idea what happened, but it almost seemed like doing that caused the PIA to remember what it was supposed to do. Pin 8 went from incorrectly reading normally high to reading normally low. Removing the jumper to pin 8 showed no closed switches. When I replaced the column and row connectors all the switches tested fine. The game has been running great for about 2 days now.

It bothers me that I have no idea what "fixed" the issue, but I am glad that it is working.

Good idea. I grabbed a few spare inverters, but not the PIA. I'll have to find some. Thanks for all your help, I really appreciate it.