You are in a bit of a bind!

Because 'get it done quick' would be very difficult if I were in your position.

Troubleshooting this exact problem is absolutely quick, easy and trivial, if you have a Leon chip.

I'm sure you are familiar with this page:

https://www.pinwiki.com/wiki/index.php/Leon_Borre_Data_East_CPU_Board_Repair

Here is a video:

Matt's Basement has the eprom I use:

https://mattsbasementarcade.com/product/leon-borre-test-roms/

Choose the Williams System 11/DATA EAST MPU version.

Once you have a 'Leon chip' in mere moments you can find the broken solder connection, the defective PIA that is causing your problem.

The reason it's so convenient is that it pulses the appropriate lines slowly, allowing you to see clearly with a logic probe if the signal is present, or clean enough. If you are using the game eprom it's a lot more difficult to see if the lines are cleanly pulsing high and low.

Of course, if a line to a PIA is suspect, putting a replacement PIA in a socket is something you do a lot of with these boards.

Personally? I would tell your customer that they will have to wait until you get a diagnostic chip in, order the chip, and use the Leon Chip to find/fix your problem.

I think that the first half dozen Data East/System 11 board problems I repaired took me a LONG time. I'd be willing to bet that I've repaired thirty boards with the Leon Chip in the time it took me to do my first half dozen without it. It's an unbelievable time saver for board repair.

Good luck, and post what you find!

This is poor help, but...

"It's gotta be something..."

A lot of board repair comes down to just not being willing to give up.

You have to persevere and keep working on it when it no longer makes sense to do so.

I can't tell you the number of things I've fixed just because I kept on it longer than all of the other techs.

Two helpful things for my approach:

Stop doing, and think. In particular, think about what the board's condition is right now, not where you started, not about what you've already fixed. Think very carefully about what the board is doing right now, and how you would approach that problem. Don't think 'well, I'd replace the PIA, but... I... already... did... that...' That's a loop that stops your creative problem solving.

When I'm stuck, I have to approach it as if it were a problem that is new to me. Re-examine things step by step and don't allow myself to consider what I've already done. Examine it as if it was someone elses work.

The second thing that is helpful for my approach is Randy Fromm's board repair technique.

Get the schematic that shows the section of the board you are looking at.

Enlarge it if necessary, but make a photocopy.

Test something. Maybe a chip. When that part has been completely tested good, or better yet replaced, use a yellow highlighter on that part of the photocopied schematic. When a wire goes somewhere, check the trace on the board. Then highlight it on the schematic.

When your schematic is all yellow you've solved the problem.

These methods have been very helpful to me.

Good luck, and let us know what you find!

Awesome!

A know a few people here on pinside are much better board repair guys than I am, and their advice is to NOT replace the part with a new part 'just in case' (shotgunning is the technical term). They have been bitten by bad parts being mailed to them (frequently from China), and have had more problems with suspect parts fresh out of the package than they have had problems with suspect parts on the board.

Don't change all the parts! That's a pretty good battle cry.

In particular, this (shotgunning) method of board repair should only be done a stage at a time... put in a part, test. Don't pull five 40-pin chips and wonder why things aren't working now! Anyway...

So.

Bad part.

Good find.

GREAT troubleshooting!

SUCCESS!!!