Williams NVRAM module?

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My Robotron is losing bits and pieces of the high score table and since my buddy and I are in constant battle for the high score (playing 5man TGTS and have lost a few 800k+ scores now) I have decided to do the Williams NVRAM module MOD http://www.robotron-2084.co.uk/techwilliamscpunvram.html

Does anyone know where to get this board, I would like to find a supplier before I go and try and make my own.

Thanks
-Ken
 
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I'm in the same situation with my Joust. (I don't have record high scores or anything, but it's still annoying to lose them.) Please let me know if you buy or build. I just put together an online order for the parts to build an adapter, but I'd be interested to know what you end up using.
 
Well, since those boards are no longer made you have 2 options.

A. Make your own

B. Pull the switcher out and install an original linear power supply.
 
I rebuilt the original power supply and it works pretty well but is to unreliable to play any real length of time on. I am probably going to get some boards manufactured. I think I'll do a run of 100 and sell off a few to recover the cost. I'll keep the forums posted.

-Ken
 
I rebuilt the original power supply and it works pretty well but is to unreliable to play any real length of time on. I am probably going to get some boards manufactured. I think I'll do a run of 100 and sell off a few to recover the cost. I'll keep the forums posted.

-Ken

If it is unreliable, then it is in need of additional work. The original Williams linear power supplies are extremely stable. What are the voltages you measure at the RAMS and how much AC ripple are you seeing?

ken
 
Isn't your problem a problem with the 5114 cmos static ram? I have a bad Stargate Rev A board and I'm guessing this is my problem with my bad high score table and error screen of cmos error.
 
I'm seeing the same thing many have seen after switching out the older power supply for modern switchers. It is very stable with the newer supply except for the high score table losing scores once in a while.

As for voltage and AC ripple I will hook it back up and check. I was running like 5.1v but never checked for AC ripple.

I'll report back what I find. I did all the parts in the rebuild kit from Bob Roberts but that doesnt mean there is not some other issue with it.

-Ken
 
Switching to NVRAM won't help losing the scores and settings. That is an effect of the power shut off characteristics of the 6809. As power dips below a certain point, it will randomly write into memory based on register settings. If those memory addresses just happen to be the CMOS (or NVRAM), bye-bye high scores. The Williams linear power supplies continue to supply +5V to the CPU for a couple of milliseconds after the +12V unregulated goes away. The loss of the +12V triggers the memory protect circuit that prevents the CPU from blasting your scores (and settings).

So switching to a NVRAM will only help you not lose scores &/or settings when the batteries (or battery if you have done the lithium battery mod) die. It won't do anything to stop the switcher induced CPU rampage across your CMOS.

As a secondary point, it is a good idea to check your switcher monthly just to verify the output voltages. They will drift overtime. Sometimes they will drift lower, but I have had several that drift higher and will fry boards.

ken
 
The Williams linear power supplies continue to supply +5V to the CPU for a couple of milliseconds after the +12V unregulated goes away. The loss of the +12V triggers the memory protect circuit that prevents the CPU from blasting your scores (and settings).

If this is the case, couldn't we just put a big-a$$ed cap across the 5v of the switcher to hold the 5v a bit longer?
 
I believe he was talking about doing it with a big cap and the switcher. I have read about this a little but noone seems to have any real information. Anyone have any thoughts?

-Ken
 
I believe he was talking about doing it with a big cap and the switcher. I have read about this a little but noone seems to have any real information. Anyone have any thoughts?

Yep, that's what I meant. I was talking to someone who happens to be a member here about this very issue, and was told that he put a 10,000uF (or higher) cap on his test rig switcher and it seemed to help. Should this be a new thread rather than hijack the nvram question?
 
If this is the case, couldn't we just put a big-a$$ed cap across the 5v of the switcher to hold the 5v a bit longer?

Several people have tried this with mixed results. In one case, it burned out the switcher because of the high current draw across the +5V on start up. In a couple of other cases, the draw kicked the overcurrent circit on the switchers and they shut down (I am assuming the one that burned out was a cheap chinese knockoff of the cheap chinese knockoff switchers).

The only real way to do it would be to add current limiting resistors and a voltage regulator to make sure the power remained stable. Oh wait, that is a linear power supply being supplied by a switcher.

It is cheaper and safer to just rebuild the original ps board. Both Dockert & I do them all the time. You can also get the parts from any electronics supply house (except for the 18,000uF cap. So far GPE is the only place I have found that stocks them.) if you want to DIY.

The originals lasted 20+ years with little to no maintenance in an arcade environment. Why mess with a good thing?

ken
 
I rebuilt the original power supply and it works pretty well but is to unreliable to play any real length of time on. I am probably going to get some boards manufactured. I think I'll do a run of 100 and sell off a few to recover the cost. I'll keep the forums posted.

-Ken

Wanna sell me your transformer then? :) My Joust had a switcher installed when I bought it, so although I have an original (disconnected) power PCB, the part with the transformer is missing. If I had it, I would certainly toss the switcher and rebuild the original supply, both to avoid high score loss and to have everything as 'original' as possible.
 
The originals lasted 20+ years with little to no maintenance in an arcade environment. Why mess with a good thing?

ken

IIRC, Defender has no over voltage protection in the linear supply like Joust and Robotron have. Stupid things like shorted coin door lights could do damage to the boards. The reason I like a switcher for Defender is to isolate my boards from things that could do them harm. Perhaps the best solution for Defender (and maybe some early Stargates) is to upgrade the linear to the newer design, but the switcher is quick, easy, inexpensive, safe and ubiquitous.
 
IIRC, Defender has no over voltage protection in the linear supply like Joust and Robotron have. Stupid things like shorted coin door lights could do damage to the boards. The reason I like a switcher for Defender is to isolate my boards from things that could do them harm. Perhaps the best solution for Defender (and maybe some early Stargates) is to upgrade the linear to the newer design, but the switcher is quick, easy, inexpensive, safe and ubiquitous.

The Defender power supplies do not have the overvoltage protection of the Robotron and later ps boards. But bad GI lighting will not result in damage to the game boards. The power for the GI lighting is drawn directly from the transformer and is fused by F5. Any shorts in the GI circuit will result in a blown fuse but will not cause an overvoltage situation in the CPU boards. The most common overvoltage failure is a short in the 2N6057 transistor allowing 12.8 VDC through the +5VDC side of the power supply. This is fairly rare. It was most common in situations where the machines were packed back to back in an arcade, run 24/7 in a hot environment and insufficient airflow caused the transistors to overheat and fail. In most home settings none of these conditions should occur.

If you are worried about the overvoltage, you can get one of the overvoltage boards that appeared on Stargate or make one yourself. The schematics and parts layout are in the Stargate manuals. Or you could upgrade to a newer ps board. The only tricky part is mounting the heat sink. The best mounting I have seen involved mounting the heat sink on a block of wood mounted on L brackets so that the block of wood stuck up vertically off the power brick base. That gives you all of the protection of the newer circuit with preserving the original power brick.

ken
 
If you are worried about the overvoltage, you can get one of the overvoltage boards that appeared on Stargate or make one yourself. The schematics and parts layout are in the Stargate manuals. Or you could upgrade to a newer ps board.

Hmmm, this may be my next upgrade. :)
 
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