Fixed - Pole Position Dallas sram problems

Jaydon

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Donor 2020-2021
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I have a Pole Position board set that works perfectly with the stock 6116 ram installed at 7E. The battery was removed and there is no damage to the board caused by the battery leaking.

20250903_161620b.jpg

I am trying to install a Dallas DS1220AB-200+ in place of the 6116 @7E. But when it is installed, I get the dreaded RAM 8 error.

What I have done so far:

Verified I am getting 5.02v at both ends of the CPU board.
Verified I am getting 4.99v at pin 24 of 7E
Verified that pins 18 and 20 of 7E reach 0.06v upon game bootup
Verified the resistor values in the battery backup power circuit are within specs.
Q2, Q3, Q4 tested good. But replaced in case they were failing under load.
CR6 was incorrect value originally (from factory). Installed correct value from manual.
Also verified CR2 and all the resistors around the LED.
Tried a second Dallas DS1220 in case the first was faulty.

When I increase the voltage to 5.05v, the monitor flashes back and forth between garbage on the screen and the RAM 8 error screen.

Any ideas on where to look next?
 

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I figured this out. I tested for continuity to and from everything connected to 7E and the ram battery backup. There were no trace brakes. I then de-soldered and replaced two of the 1K resistors for being borderline out of spec. Nothing changed. I still got the flashing between RAM 8 and and scrambled garbage whenever the DS1220 was installed. I figured the game was resetting. So on tried swapping out the Z80 and crash (the game start up sound), it worked. For some reason, the Z80 would work with the stock 6116 ram, but not the DS1220.
 
Sounds remarkably familiar to this...
 
Sounds remarkably familiar to this...
I'm not going to lie, it might have been where I got the idea from. 😂

I read your repair log the other day when I was thinking that I might have had to install a coin cell battery, like the one that originally on that board set you repaired. But after reading your post, it got me thinking that maybe my 2 screen flicker was the z80 resetting. Instead of breaking out the logic probe, I just swapped in a new z80.

Once again, @lilypad19 , I owe you. 🫡
Thank you.
 
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