Gilligan's Island
Bally, 1991Ref this post: https://pinside.com/pinball/forum/topic/volume-suddenly-at-maximum-wpc-hurricane#post-6866321
It looked like rlbohon3 was able to source the U5 (X9C503) IC in ref. post. I'm working on a game that may need U5 (X9C503) replaced. I'm having trouble finding that IC, but there is a Maxim IC that is available and looks like it may be a compatible replacement (DS1804-050). Does anyone know if the Maxim chip will work as a substitute for the X9C503?
It looks like marco has it.
https://www.marcospecialties.com/pinball-parts/5432-12726-00
I don't have time to do the comparison right now, but at a glance the two chips to appear to be similar. Datasheets:
I should have asked this...The problem the customer is having, is as follows:
The game is set to (made up numbers here) volume 10. The volume stays at the set volume the entire time the game is ON. After coming back the next day or whenever, the volume is at 7 (or some other setting). So I was thinking it might be bad memory in the U5 chip.
I looked at Marco and didn't find that, but I didn't think to search on the old part number. Thank you.
I always assumed it was the MPU's RAM where the volume level was saved, since all other RAM chips were volatile RAM since there was no battery to back them up.
If you look at the datasheet, the X9503 has on-chip nv-ram that is used to save the setting. I assumed that's what was used, but I don't really know.
EDIT...
Here's a paragraph from the datasheet:
When the device is powered-down, the last wiper posi-
tion stored will be maintained in the nonvolatile mem-
ory. When power is restored, the contents of the
memory are recalled and the wiper is set to the value
last stored.
I don't know either. I never had the need to do a deep dive on how the volume control feature actually worked.
Quoted from KenH:There are not a lot of posts about that IC and nothing about the volume changing between power ups. It is the only thing I can think of to try to solve the issue.
If the game's screen is reporting that the volumne is at "7" where it was at "10" last time, that's NOT a function of the 9503 - there's no way to 'read' its current value, just set it.
If the game's screen is showing 7 vs 10, then that's an issue in the game's software/MPU/Sound Board processor... The volume level's stored in the game's RAM..
OK it looks like the volume does have a number -- I found a video on youtube.
If it is not U5 causing the problem, I'm not sure where to go next. Coyote comment makes sense -- there is no obvious way to read the current setting on U5, unless the CPU somehow measures the current volume resistance and puts a number on it when the game starts.
Let me know if anyone has suggestions on how to troubleshoot the problem further.
Thank you.
Quoted from KenH:OK it looks like the volume does have a number -- I found a video on youtube.
If it is not U5 causing the problem, I'm not sure where to go next. Coyote comment makes sense -- there is no obvious way to read the current setting on U5, unless the CPU somehow measures the current volume resistance and puts a number on it when the game starts.
Let me know if anyone has suggestions on how to troubleshoot the problem further.
Thank you.
Do you have any other WPC games where you could swap MPU boards to see if the issue remains or is resolved?
Since it is the Ram chip for the game that stores the volume setting, you have a 'settings not held' problem.
So. Replace the batteries. Examine the battery contacts, make sure there isn't anything tarnished, corroded, and that the pads aren't falling apart. Pro tip: Replace the batteries with the power on and you won't lose any high scores or settings.
Measure the voltage at D2 according to this section of the pinwiki:
https://pinwiki.com/wiki/index.php/Williams_WPC#Settings_Not_Held_or_Battery_Depletes_Rapidly
Personally, every chance I get I'm replacing the ram chips with NVram replacements.
This requires installing a socket, which is not an easy thing to do if you haven't done this kind of work before.
If the settings ram is getting corrupted somehow, either the battery isn't supplying good power to hold the settings, or the ram chip itself is the problem. It's better to get rid of the batteries entirely by installing NVram, and that also replaces a potentially bad ram chip.
(I'm glad you aren't finding this to be the volume control chip. I've had only two of these fail, and both times they went to full volume that couldn't be turned down. Replacing the chip solved the problem in both cases.)
Robotworkshop Good idea, but this is a friend's game and neither of us have any other WPC games.
PinRetail He said he recently changed the batteries and there are no other issues of lost game settings or errors displayed. But its a great idea and I'll make sure the voltage is >3.5V at D2, and double-check there are no startup errors, and verify one 'bong' at power on. I'll report back with the results.
I appreciate the suggestions...keep the ideas coming 
Quoted from PinRetail:Personally, every chance I get I'm replacing the ram chips with NVram replacements.
This is a really good idea, which I should do even if it does not solve this problem. I've changed all my games to the RAMTRON (I wish they still made the PDIP version!) and never had a problem.
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Sierra Vista, AZ