Williams classic hardware voltage issues and fixes

mecha

Well-known member
Joined
Apr 19, 2007
Messages
24,349
Reaction score
7,057
Location
MKE, Wisconsin
at work we have Defender, Stargate, Joust, Robotron, and Sinistar .. I gave all of these my "OCD treatment". the OCD treatment consists of new filter caps, headers, and plugs on the MPU and rom boards, and the linear power supplies got new caps, headers, voltage regulators, bridge rectifiers, and 2N3055s.

a friend of mine's Joust had morbidly low voltages with both the linear and switching power supplies. so this time I decided to go step by step on what can give your voltages a boost.

first I did new filter caps on the MPU and rom boards, as well as upgrading the ram to 4164s with the trace mod. this wasn't as effective as I believed it to be, the voltages didn't reflect so much of an increase. this doesn't mean you shouldn't replace these caps, I think it was more an issue with the source voltages coming in.

next I tried replacing the plugs with Molex parts. I saw a subtle increase by doing this. the CPU board I think was still at about 4.6V and the rom board at 4.33. the game was actually throwing a rom error 1 code.

I absolutely despise the factory headers. I don't like their skinny and round shape, as they have reduced surface contact compared to proper headers. replacement of the headers brought another subtle increase in voltage. at this point I wound up tapping into the switcher with the Bob Roberts adapter for using the existing wiring. now the game actually booted properly, and with easy voltage adjustment access, I was able to bring the voltages up a bit more.

the reason I point this out is because the linear power supply was never rebuilt. even though it's output voltages seemed sufficient at 4.95V, there's some kind of a wiring glitch in there someplace. the rom board actually ran fine with the linear after doing caps, plugs, and headers, but the MPU was still a bit low, at around 4.7V.

the switcher was adjusted to 5.10V, I got 4.95V out of the rom board then and about 4.8 out of the MPU. it's worth noting that there are unused pins on the MPU power plug, my next goal is to try testing voltages with an additional +5 and ground wire.

the moral of the story is if you want your power to reach its best potential you have to replace ALL of these parts. all replacements can be obtained from Great Plains Electronics, including all the necessary parts to rebuild the power supply. while these games can run at insanely low voltages below the usual 4.75V tolerance, if you're having problems with your game you owe it to yourself to address the power issues first.

I'll include a parts list when I complete my next order.
 
Last edited:
I absolutely despise the factory headers. I don't like their skinny and round shape, as they have reduced surface contact compared to proper headers. replacement of the headers brought another subtle increase in voltage. at this point I wound up tapping into the switcher with the Bob Roberts adapter for using the existing wiring. now the game actually booted properly, and with easy voltage adjustment access, I was able to bring the voltages up a bit more.

Thanks for posting all your info/experience. It's probably not needed in many cases, but I tend to replace the male header strips on stuff, but ESPECIALLY the round pins. The added surface area/contact can't hurt!
 
Thanks for posting all your info/experience. It's probably not needed in many cases, but I tend to replace the male header strips on stuff, but ESPECIALLY the round pins. The added surface area/contact can't hurt!

I despise the original headers. but yeah, I guess you have to change all 3 parts after all lol

the shop is closed for electrical work, upon my return I'll see what kind of results adding wires will bring. I actually find it incredible these boards run with single voltage wires. I guess with the tri-voltage ram though it didn't matter as much.

I've done a couple 4164 upgrades with original power supplies and the games weren't able to boot anymore. this one last night for whatever reason still did with the voltage low to the MPU. so it may be a "your mileage may vary" thing. I didn't however replace the main power plug that comes off the linear, and the switcher has a Bob Roberts adapter, so it might be losing voltage off the adapter. I always observed before I worked on this game that the MPU got a little less than the rom board.
 
Back
Top Bottom