Hello All,

I am working on a saving a REALLY bad shape Whirlwind. Game appears to have been left in a barn or a field. Tons of rust. A total disaster. My approach has been to work through the boards first to see if I can save them. I am a hobbyist, not an expert.

Thus far, I am happy to report I can get the board to boot on the bench. I replaced sockets for EPROM and all the PIA chips. I am now trying to get the display to work so I can troubleshoot through the traditional test report menus on system 11 games. I should note - I have a 100% working Taxi that I am using as a test fixture.

I have hit my first roadblock trying to get the display to work. Attached pic is what is coming up. Any idea where on the board to try to fix this garbled text?

Based on the schematics, I know that PIA's at U41 and U42 control the display. I have socketed and replaced both of these. I have used a logic probe and compared both of these to my working Taxi CPU so I know they are working.

What is the next step to fix this display output?

display (resized).jpg

More info and pics of the board -

I cut off the original battery pack (with batteries still attached) and there appeared to be no leaking.

I am also finding the thru-holes and traces are very clean and intact when I remove/replace IC chips. I am buzzing all traces out after socketing the chips to confirm my work.

So I dont think it has alkaline corrosion. There is some corrosion in the switch matrix part of the board (pics) that you can see. I think this is more oxidation from being exposed to the elements than alkaline corrosion. But I obviously have not got to the switch matrix portion of this salvage without the display working.

mpu2 (resized).jpg

mpu3 (resized).jpg

mpu4 (resized).jpg

mpu5 (resized).jpg

mpu6 (resized).jpg

Thanks Cheddar, yes all of those sockets you see are my work. I was shotgun replacing several IC chips that I likely didn't need to replace. I later realized that the factory installed ROM sockets were the culprit preventing boot up.

Looking at the schematic, those SRC's appear to be the only component in line with the PIA and the display header. Would that mean this is the likely culprit for the garbled display?

Is this a common component? I looked up by part number on Marco Specialties and cannot find it. According to manual it is a

SIP, 9R, 10 pin, 2.7K ohm, 470 pfd,

Anyone know a good lead on these?

Are there other board components that would affect the scrambled display?

schem (resized).jpg

The display is the one in the working Taxi so I know the display and display board are 100% good.

Update - I moved both CPU boards to my bench power supply. I am just going thru the PIA's associated with display and comparing them from working board to non working board, came up with this discrepency

PIA U42
pins 10-17
Taxi (working board): Logic probe buzzes 'Low'
Whirlwind (project board): Logic probe buzzes 'High'

I am no expert with logic probe, but trying to compare these two identical boards has been my approach.

Again, the PIA in the Whilrwind board is brand new.

Any other areas of the board I should trouble shoot?
cpu2 (resized).jpgpia (resized).jpg