Roadtrip 6/1-2017 Atari Dominos Pickup for Kralleman

[smarty]

@Pinge, thanks for those CP images, It gives me an idea of what one should look like. They are great for now, at some point I may like a close up of the Domino logo in the middle so I can reproduce it.

@Kralleman, You're making progress well done So the 7432 at P3 is an or gate, if either input is high you will get a high output, because pin 10 is always high the output will be held high. Like you say tracing that back to the 9301 at D2 show all of those input signals on pins 1,2,14, & 15 are pulsing it is highly likely D2 is faulty. You'd really need a logic analyser to confirm the timing of the input signals which should trigger the output on pin 7, be in reality I'd say swap D3 out and forget about needing any higher tech knowledge.

These 9301's are not available anywhere anymore I'd be interested to see what data sheet you found and what that seller was actually selling?

Take a look at my Super Breakout repair thread I just posted in the tech forum. I've had a batch of boards made up to replace the 9301 with a 7442 which is essentially the same device with a different pinout and is readily available, PM me your address and I'll send you a few of them

[Pinge]

I can try yo take a better photo of the cpo/logo this week aswell.

[kralleman]

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@Kralleman, You're making progress well done So the 7432 at P3 is an or gate, if either input is high you will get a high output, because pin 10 is always high the output will be held high. Like you say tracing that back to the 9301 at D2 show all of those input signals on pins 1,2,14, & 15 are pulsing it is highly likely D2 is faulty. You'd really need a logic analyser to confirm the timing of the input signals which should trigger the output on pin 7, be in reality I'd say swap D3 out and forget about needing any higher tech knowledge.

I hooked up my scope and the signals going into D2 are looking like clean pulses (as opposed to just garbage). I have an old logic analyser stashed away in the attic but I have yet to make some room for it and learn how to use it. Saving that for a rainy day

These 9301's are not available anywhere anymore I'd be interested to see what data sheet you found and what that seller was actually selling?

The datasheet was this one and the eBay auction for NOS ones is found here.

Take a look at my Super Breakout repair thread I just posted in the tech forum. I've had a batch of boards made up to replace the 9301 with a 7442 which is essentially the same device with a different pinout and is readily available, PM me your address and I'll send you a few of them

Seriously? Wow that's awesome! PM is coming your way in a minute I will read through your SB thread too.

[kralleman]

I got the replacement for the 9301 from Smarty today! Thanks a lot, I owe you!

Unfortunately, my problem persists after I swapped the 9301@D2 for the new replacement. The output from pin 7 is still high which in turns pulls the output at pin 8 from the 7432@P3 high. The inputs to the 9301 (as well as the new replacement) at pins 1, 2, 14 and 15 all have clean pulses when I look at them with a scope. I'm confused. Could the clean-looking pulses coming into the 9301 be incorrect?

EDIT: Actually, the signals of the pins 1, 14 and 15 (the three that have signals coming from the 6401(?) decoder) of the 9301 all look very similar in when looked at in a scope. The signal on pin 2 (the one marked R/W) is the only one that differs. It looks to me that at least one of the three signals coming from the decoder needs to differ in order for pin 7 of the 9301 to ever go low. For pin 7 to go low, if I understood the datasheet of the 9301 correctly, the following needs to happen:

Input Pin1: Low
Input Pin2: High (the only one with a signal that seems to differ)
Input Pin14: Low
Input Pin15: High

As it looks right now, pins 1, 14 and 15 go low at the same time and high at the same time. Then again, my scope is from the seventies or something and the picture isn't the sharpest

[Pinge]

Your game is from the seventies aswell so the scope should be fine 

[smarty]

 Shame the IC didn't fix the problem, I will try and digest what you've written in the next few day and think of some other areas you can't test. I'll take a look at the Ops manual as they are pretty descriptive in he theory of operation for these early boards.

Can you confirm that the pin that is stuck high isn't shorted to the 5v rail probably on a trace on the underside of the PCB or any other signal nearby.

Give the ROM legs a clean too with a light rub from some sandpaper or similar if you haven't already.

[kralleman]

Thanks for the input! I am in no hurry so no rush in digging through the manual. I am just thankful that you want to juggle this problem with me at all I will go back to the manual myself and have a look.

I double checked the line now to see if it was shorted to 5v or anything nearby. I couldn't find anything in between the 7432@P3 and the 9301@D2 that it was shorted to. I also checked the 7432 to see if it was maybe internally shorted and same with the 9301-replacement. No shorts there either. The 7432@P3 is a bit burnt on its legs, could it be bad without showing a short between pin 10 and any other pin?

I gave the pins of the ROM and the pins of the 7432 some love now too. I'm finding that a fiberglass pen is great for that sort of cleanup tasks. Board is still showing same symptoms though.

Also worth mentioning is that I have this rigged to a switching ps on my test bench and that I am only supplying the PCB with +5v from that (i.e. no 12v or -5 or anything like that is connected). I'm pretty sure that I looked at the schematics to verify that no odd voltages should be required for these parts of the circuits.

[kralleman]

A small update: tried replacing the 7432 @p3 but it did not change anything. Will have to allocate some more time for this pcb soon.