Updating the Pac 4-in-1 hack

[Lindsey]

Where on the board are you testing the voltage?
Mine 4.9v near the edge connector and ~4.75 on pin 24 of the nvram

You'll definitely want to check right at the NVRAM. As you pointed out.

I wouldn't expect problems until less than 4.5V but you could use a switcher and adjust so you have exactly 5V at the NVRAM just to be sure. That's what I would do...

 

[Riptor]

My voltages are stable all the way to the bottom of the board. I have checked right at the NV ram and at TTL across the whole PCB.
I really dont think this is a voltage issue. If anything I might have bad 1220's because they are old and untested. They do seem to be retaining data so I assumed they are ok. It also appears that the game is writing some sort of data to it.

 

[souzilla]

Can you try the latest rom I sent you and see if it is any different (still writing to the nvram etc)

My voltages are stable all the way to the bottom of the board. I have checked right at the NV ram and at TTL across the whole PCB.
I really dont think this is a voltage issue. If anything I might have bad 1220's because they are old and untested. They do seem to be retaining data so I assumed they are ok. It also appears that the game is writing some sort of data to it.

 

[Riptor]

Sure will, plan on doing that real soon. I just got home from work.

 

[souzilla]

D'oh

I never really looked at the pinouts for the 2114 ram before.
After looking at the schematic it looks like it is wired up in an unusual way.
http://www.souzaonline.com/temp/pac_2114.JPG

So, one of 3 things is going on.
1. I am too tired and need some sleep
2. The Pac board does something wierd with the ram addresses
3. There is a typo on the schematic

I have not tested this theory out, just thinking outloud I guess.

This would actually explain why it is writing garbage to the nvram.
So I guess dropping in nvram into one of the empty eprom sockets may not work.

Either it would require a good deal of hacking or someone would need to make a small adapter board.

 

[Riptor]

I wouldnt be surprised to see a typo in the pac manual. The manual is full of typos. I havent run across any in the actual schematics that I remember.

I just burned the new file and tested it out. Its working much better than before but still not saving scores. It started mspac off with no high score like it should but pac always has a HS of 8800. It only actually let me input initials once and that was on mspac.
All this was done with the existing NVram and whatever data was left on it from previous tests. Im getting ready to clear it and reinstall the seed file to see what it does and what is getting written to it, if anything.
Jason, PM me if there is anything specific you would like me to try out.

 

[Riptor]

Any pictures of the setup?

Here's a pic

 

[Lindsey]

I wouldnt be surprised to see a typo in the pac manual.

I checked with a meter and the schematic is correct. At least the 2114 section...

I'm considering making the adapter boards.

 

[souzilla]

I'm considering making the adapter boards.

That would be cool... I am writing how to make an adapter by hand. It should not be too much additional work than the original design. Just using a wire wrap socket and a normal socket to reverse the address lines. I will test this tonight and if everything works out post everything. I am hoping for version 2.0 of the 4-in-1 mod out very soon (once this is confirmed).

Also, thanks to everyone for all the great feedback.
The updated code supports
- 3 letter initials only for now.
- Seperate HST for each game
- enhanced UI from the original version

 

[SeanMcL]

Awesome. You have certainly gone above and beyond the call of duty on this one.

Should you be able to coin up or start a game from the HS screen, or is that not possible. It almost looks like the game supports no inputs at that screen. Even on free play a game will not start. Maybe it only happens in MAME, or did I miss an earlier explanation?

Thanks again, Jason.

 

[souzilla]

Should you be able to coin up or start a game from the HS screen

Thanks again, Jason.

Final release supports this

 

[souzilla]

I probably won't get to it this weekend... too much other stuff going on.
If anyone else wants to take a crack at it let me know

 

[Riptor]

Hmmm, I wont have time either, working the next couple nights.

 

[souzilla]

Also, the data lines are backwards.

D'oh

I never really looked at the pinouts for the 2114 ram before.
After looking at the schematic it looks like it is wired up in an unusual way.
http://www.souzaonline.com/temp/pac_2114.JPG

So, one of 3 things is going on.
1. I am too tired and need some sleep
2. The Pac board does something wierd with the ram addresses
3. There is a typo on the schematic

I have not tested this theory out, just thinking outloud I guess.

This would actually explain why it is writing garbage to the nvram.
So I guess dropping in nvram into one of the empty eprom sockets may not work.

Either it would require a good deal of hacking or someone would need to make a small adapter board.

 

[Riptor]

Also, the data lines are backwards.

Wish I had seen the BEFORE building the adapter instead of 5 minutes after I finished. Back to the drawing board, going to start from scratch.

 

[souzilla]

Posted and a new threads started

http://forums.arcade-museum.com/showthread.php?t=113971