I have a Gottlieb Volcano (model 667, system 80)

I had it all working great... MPU reset modification. Booting great. I previously had an issue where the RAM appeared to be flaky because it was not retaining anything consistently and random scores coming up. Then I fixed several problems with the 110 VAC coming into the machine and I had no more of those weird issues for last several days.

Today I socketed the 5101 (Z5) Ram chip so I could install an NVRAM from PinballElectronics.com. (I remembered to remove the memory capacitor)

The NVRAM chip went in and seemed to work, but every time I start a new game, the high score is wiped out and replaced with the default high score 790,000. Credits are retained and other bookkeeping appears to work. The score is retained correctly through a power down/up cycle. It's just starting a new game that wipes it out. I went through bookkeeping and zeroed everything out; makes no difference.

I put my original 5101 back in and now that's doing the same thing. So whatever is happening apparently has nothing to do with the RAM chip itself.

I checked the new strip socket carefully and see no issues there.

Suggestions? I don't even know where to start. Thank you!

Z5 top

Z5 bottom

I'm now suspecting Z36... it's close enough to the battery damage area and it's not testing out consistently.

It's supposed to be a 4069 CMOS. According to the manual...

manual

It says MM74C04 or SCL4069B

Only two gates are used. One gate at pins 1 & 2 and another at 8 & 9. When I used my DMM in diode mode, red lead on ground, the two gates test fine. However, out of the other four gates on the chip (listed as spares in schematic) two are testing as dead shorts. This makes me want to change this chip, but I do not have a 4069, and PinWiki is not showing any acceptable substitutes.

Secondly, I want to test these gates in the game with my logic probe... can anyone tell me what the inputs/outputs should be when a new game is started. I'm not even sure if this is going to be able to tell me anything. What are OD and CE1 on pins 18 & 19 of the 5101?

Z36

Capacitor C25 is also close to the battery damage area. Although cleaned up, I think it best to replace. The schematic parts list shows it as a 0.1uF 50 volt cap. However the only 0.1uF caps I have on hand are 35 volt tantalum. Looking at the circuit, since it's part of the 5 V logic, I assume my 35 V cap should work out fine? (If it matters, I did the reset modification, so many of the parts in this schematic including the Z1 have been removed.) Edit: I replaced the cap but it makes no difference.

C25

Yes, that is default high score. However, you can zero it out in bookkeeping step 14. You can even set any high score you want using step 14. That’s how it used to work until today. Until this morning, I had 351k on it all week.

After I zero it out and play, the new score shows as high score. Then when I hit the start button, it’s immediately replaced with 790,000. This is not normal.

FFA7D64C-2139-4E44-A40C-9B5A0B3D6F20 (resized).jpeg

1AD9549E-5443-4646-A7F6-AE3A32E0D12B (resized).jpeg

Such a comedy of errors with this whole thing.

So with the original 5101 RAM chip and no battery, on powerup the game automatically sets bookkeeping:

Step 11 to 400,000
Step 12 to 700,000
Step 13 to zero (optional I think)
Step 14 to 790,000 (HSTD)

However with the NVRAM all of these steps are initially garbage characters. So I zero'd all the bookkeeping steps out, but step 14 kept setting itself to 790,000 on game start no matter what I did.

Then at one point with the new NVRAM, thinking I needed to match the original RAM, I set:

Step 11 to 400,000
Step 12 to 700,000
Step 13 to zero
Step 14 to zero

Still no good! (Realized later steps 11, 12, and 14 need to be ascending values and step 14 cannot be zero.)

Finally, I set:

Step 11 to zero
Step 12 to zero
Step 13 to zero
Step 14 to 100,000

Now, as soon as I reached 100k, it's saving the current high score; no more 790,000!

Thank you again to @chrishibler! After your comment, I manually set Step 14 to 820,000 as a test and it was retained after each game start... that was my best clue.

Agree! And thank you for maintaining it.

Maybe also add that a 5101 chip is not required for boot on the system 80 MPU. And if you boot without a 5101, you get 8 credits and 888,888 as the HSTD on all displays. Somebody in another thread was talking about seeing the 8 credits and 888,888 but did not know his 5101 was bad/dead.