pole pos HSS mod didn't work

TheShanMan

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I've got a PP2 cockpit and did the mod as discussed here with the schottky (1n5817), a cap (47uF), and a ds1220ab. Yet it is not saving scores. I assume the mod works on PP2 just the same, right? I used an electrolytic for the cap - I assume that's ok? Tried 2 different ds1220's so unless the run was bad that should be ok. The band on the schottky is on the Vbatt side.

The battery holder was eliminated from the circuit before I got it, but I assume any battery elimination that was done wouldn't have involved a destructive modification of the circuit.

Anyone have an idea of what might be wrong or what I should check?
 
I'll check it tomorrow. Does the Dallas chip have tighter tolerance for supply voltage than the other components on the board would (since the game plays fine)?
 
I'll check it tomorrow. Does the Dallas chip have tighter tolerance for supply voltage than the other components on the board would (since the game plays fine)?

Well, kinda but not really. What happens is the board functions fine with 5v or a little under. Add the NVram which is designed to go into a write protect state if voltage falls below a certain point. If your voltage is close to or below this threshold then the game wont boot. If I remember right, the AB version is not as sensitive as the Y version. Cant say for sure without pulling up the datasheets, might be the other way around. Either will work if you compensate your voltage for it.
 
I'll check it tomorrow. Does the Dallas chip have tighter tolerance for supply voltage than the other components on the board would (since the game plays fine)?

If the voltage goes below a threshold (usually around 4.75) then it won't work correctly... then again, I don't think many people have many issues with PP board have'ng too LITTLE voltage... they don't smoke themselves from lack of juice.

To answer that last question though... yeah, to an extent, I ran into it on my Tron and just yesterday on my Time Pilot 84 (modded for HSS)... voltage was 4.78 on that one, game played perfectly, but the scores were screwing up. Same with Tron, played perfectly, but scores/settings weren't being saved correctly.
 
I think we're on the right track here with the voltage. The upper ARII was at 4.8v (lower was at 5.12v). I adjusted it up to 5.12 to match the bottom and now the game won't boot with garbage and "RAM 8" on the screen. Switching back to the 6116 causes it to boot. The main board however is getting well under 5v. So I think it's time to wire separate grounds and +5V's to the test points. I'm guessing since adjusting the upper ARII caused the change in behavior, that one supplies the main board and the lower ARII supplies the video board. But I haven't verified that yet.
 
Sounds like you have edge connector issues or another connector in the harness. Start at the AR board and work your way to the pcb. Note the voltage drop as you go. You can expect some so compare your notes and see where the larger drop is. First suspect would be edge connector.
 
At the ARII it's 5.12. Touching the pin on the edge connector wire I want to say it was in the 4.8 or so range. It's possible I am remembering one of the test points though.

Since it is apparently common to wire separate supplies/gnds to each of the test points, is rebuilding the edge connector something I really need to worry about? They look decent, so my thinking is that it's probably handling non-power signals ok, and by wiring separate supplies/gnds I make that a moot point. No?
 
OK, checked various points this morning. The pin on the ARII harness was at 5.12v. The pin in the edge connector harness was at 4.94v (using ground on ARII). The 5v/gnd test points closest to the edge connector on the main board was 4.86v. The 5v/gnd test points on the opposite side of the board was at 4.83v.

Again, my thought is to do the "add extra 5v/gnd wires" mod. Sound reasonable?
 
I tried temporarily just shoving some wire into the molex on the ARII for +5 and gnd, and attaching them to the +5 and gnd test points on the board near the edge connector. It basically made no difference in board voltage.

Based on that and the fact that the voltage at the opposite end of the board is only 0.03v different than at the edge connector end, I'm now thinking my board doesn't need extra +5v and gnd wires run to the board.

However, I'm not sure if the voltage drop from one end of the wire to the other end (nearly a quarter of a volt) is expected. I cranked the voltage at the ARII molex up to 5.23v to get 5.0v on the test points of the board. Is that "to be expected" or do I need to address this voltage drop in another way?

Incidentally, as I was adjusting the pot and got above 4.95v, the game finished booting (it must keep testing rom 8 in a loop, until it succeeds). And sure enough, it saves high scores at this point. Wouldn't you know it? I got my best score by far on the first saved score - 67,400. :)

Sooo... adjust the pots on each ARII until the boards are getting 5.0v (regardless of the voltage on the ARII's) and be done with it?
 
Mine doesn't have the sense mod, but it was interesting reading your thread nonetheless. :)

Anyone have some thoughts on why there would be such a large voltage drop literally from one end of the wire to the other? It seems kind of odd to me. I can understand a voltage drop from one side of a connector to the other since a poor connection can result in high resistance, but in this case there are no connector junctions to account for it - just wire and the connector that's crimped onto it, if that makes sense.
 
No problem. Just so you know, mine read the same way. I would check voltage at the ARII, at the back of the pin on the connector at the ARII, at the pin at the back of the edge connector and at the finger on the board. It also appeared that the voltage drop was happening in the wire between the connector at the ARII and the edge connector pin. Not between the edge connector and board.

By checking the back of the pin at the edge connector you are checking the equipvelant resistance of that entire joint which is why you don't see much drop between there and the test points on the board.

As you can see from link I posted above, one componenet that I gained a good portion of voltage back was to change the edge connector. If yours is worse than mine then that may just solve your entire problem. The video board draws a lot more current than the CPU board. You could just change that connector but while your at it I would change both. It's a lot of crimping but feels good knowing you aren't going to smoke your board/ARII's in the near future.

I am sure someone else will chime in with more help. Good luck. It's a great game to have functioning well.

Murph
 
Mine's set at 5.23 at the AR TPs. I didn't use the extra cap, and my Pole Position HS's have been saved for months now. Fired it up last night, after it not having been turned on for 3 weeks to a month, and there they were. If you pull the edge connector off, and pull the board, the scores will reset. They do in my case anyway.
 
I did the NVRAM on my PP2 last nite while researching some of the older threads. Worked fine.

M48Z02/200ns that I had here. Just replaced 7E. Done.

Sounds like your voltage as stated above may be off, or rapid shut down.

Did you try a 70ns?
 
Just to document, I used just the M48Z02 70ns at 7E on mine. Nothing else. Has worked great ever since. I believe these are lithium battery backed and technically do have a shelf life. So I suppose in about 10 years I'll find out if it last longer than expected in a non-arcade daily environment.

Murph
 
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