Limon, CO
I noticed that my game attract lights are much faster than other Medusa games I have seen. Is this programming? I would like the slower pattern. Any thoughts?
(Topic ID: 148252)
Sana'a
Quoted from swampfire:Wow, that is strange. Can you try another MPU board, maybe even an Alltek?
My first thought was that it WAS an Alltek, with the MPU jumpered to run at Stern MPU-200 clock speed. But the OP stated that the board is original. It's a very interesting mystery.
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Chris Hibler - CARGPB #31
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Quoted from 5280wzrd:It does have all Bally boards. I have vector and centaur, I could try some swaps.
That would be interesting to do.
It almost has to be something with the MPU.
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Chris Hibler - CARGPB #31
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You have to confirm that both boards are using the same type of EPROMs or Mask Roms.
The usual suspects are 9332, 2532, or 2732. The board must be jumpered ( or rejumpered) to match the type of U2 and U6.
Without looking it up, some if not all 3 games may share the same U6 part number and therefore contain the same code/programming.
Quoted from CactusJack:You have to confirm that both boards are using the same type of EPROMs or Mask Roms.
The usual suspects are 9332, 2532, or 2732. The board must be jumpered ( or rejumpered) to match the type of U2 and U6.
Yup. Unfortunately. It might be more hassle than it's worth to you.
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Chris Hibler - CARGPB #31
http://chrishiblerpinball.com/contact/
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info
I went to the Sanctum last night and took a look at the attract lights. It is also fast. That just might be the way it is.
I just checked mine - each light comes on about twice a second, definitely much slower than in the video.
What DMM do you have? Can you check a frequency / clock speed?
Check the CPU clock speed. Dual clocks on the U9 CPU chip at P3 and P37. Average bally clock speed is around 0.5MHz, but the components that set the speed are 10% tolerance, so you could have something drifted out of spec.
I am not sure how much the CPU clock speed would change attract mode though. Some of that stuff is timed by an interrupt generated by the zero crossing circuit. Easy thing to check if you have the right tools to do so.
Quoted from barakandl:What DMM do you have? Can you check a frequency / clock speed?
Check the CPU clock speed. Dual clocks on the U9 CPU chip at P3 and P37. Average bally clock speed is around 0.5MHz, but the components that set the speed are 10% tolerance, so you could have something drifted out of spec.
I am not sure how much the CPU clock speed would change attract mode though. Some of that stuff is timed by an interrupt generated by the zero crossing circuit. Easy thing to check if you have the right tools to do so.
You're right, attract mode is all timed by the zero-crossing. You should check that - but you will need a scope.
CPU clock speed @ U9 P3 and P37. 5vdc around 0.5MHz
I doubt the zero crossing could be out of time, but check U10 P18 5vdc 120Hz
is it possible there is multiple game rom revisions with different attract modes?? Does anything in game act up?
Quoted from 5280wzrd:I'll bring my scope home and check into it. Game plays without problems (other than the typical fantom bumper fire). I wondered about the two rom possibility.
Maybe try different ROMs in the virtual pinball thing and see what attract mode is like
Edmonton, AB
It's also worth checking the frequency of the display interrupt generator at U12 pin 3. Should be a short pulse at approx 350Hz. It's called the display interrupt, but it's just a timed interrupt so they could be incrementing counters, etc... during that interrupt routine which could effect something like the attract mode light show timing.
I had a Stern Dracula once where everything started going really slowly. Something had gone out of spec in the clock circuit. It was really weird.
Quoted from Lindsey:It's also worth checking the frequency of the display interrupt generator at U12 pin 3. Should be a short pulse at approx 350Hz. It's called the display interrupt, but it's just a timed interrupt so they could be incrementing counters, etc... during that interrupt routine which could effect something like the attract mode light show timing.
I had a Stern Dracula once where everything started going really slowly. Something had gone out of spec in the clock circuit. It was really weird.
I've disassembled the code to the Bally system (not that particular game, but still). The display interrupt generator is just used for displays, nothing else. The zero crossing interrupt increments the counters and timers.
Quoted from hackbar:I've disassembled the code to the Bally system (not that particular game, but still). The display interrupt generator is just used for displays, nothing else. The zero crossing interrupt increments the counters and timers.
What could happen when the display interrupt us out of time the CPU could get bogged down dealing with the interrupts. When the cap/resistor drift out of spec from corrosion, I have seen it make the CPU board operate in slow motion.
Quoted from hackbar:I've disassembled the code to the Bally system (not that particular game, but still). The display interrupt generator is just used for displays, nothing else. The zero crossing interrupt increments the counters and timers.
Interesting stuff! It would be really cool to see someone post a commented decompile of some code for the classic Bally/Stern system.
We can be pretty sure that the zero cross frequency coming into the game is accurate. The power company would probably notice otherwise 
Quoted from Lindsey:We can be pretty sure that the zero cross frequency coming into the game is accurate. The power company would probably notice otherwise
pretty smart to use the 120hz from the power company as a known consistent timer.
WMS used the CPU clock and a 4020 counter to trigger the interupt. Reading the bally theory of operation, they say turning the lamps on and off between the cycles actually makes the lamps last longer due to less stress on the filament.
Quoted from hackbar:I've disassembled the code to the Bally system (not that particular game, but still). The display interrupt generator is just used for displays, nothing else. The zero crossing interrupt increments the counters and timers.
Does the code make some calculations or adjustments for when AC line frequency is only 50 Hz ( only 100 X second)?
Quoted from barakandl:What could happen when the display interrupt us out of time the CPU could get bogged down dealing with the interrupts. When the cap/resistor drift out of spec from corrosion, I have seen it make the CPU board operate in slow motion.
That's true, but in this case he said it was running fast.
Quoted from Lindsey:Interesting stuff! It would be really cool to see someone post a commented decompile of some code for the classic Bally/Stern system.
We can be pretty sure that the zero cross frequency coming into the game is accurate. The power company would probably notice otherwise
Technically the disssembled code is still copyrighted by Bally, even with my comments, variable names, marcos, etc. It's now in a weird state where both Bally and myself own the copyright. So I can't distribute it.
Quoted from CactusJack:Does the code make some calculations or adjustments for when AC line frequency is only 50 Hz ( only 100 X second)?
No. They might have made export ROMS, but I only have access to US games (and thus the ROMS). There is no frequency detection.
3 months later
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