Rom problems-

The biggest problem with Robotron is the random “carpet pattern” resets during gameplay.

“Fancy attract mode” glitch

  • Having the Fancy attract mode turned on in Advanced settings, can cause the game to reset to the carpet screen pattern.
  • Fancy attract is the moving W circles on the display screen.
  • Turn off the attract mode from Advanced settings, or F2 for Mame users.
  • This may have been fixed with the release of Blue ROMs by Williams.

“Firing in the corner” glitch (also happens in MAME)

Faulty 4116 Ram on the CPU board.

  • See Bob Roberts website for converting to 4164 ram (only uses +5v dc so doesn’t overheat, rarely fails)
  • They are 64kbit DRAM chips that when plugged into a William’s MPU board you use 16kbits of them and the other 48kbits lie dormant. They will burn out just like 4116’s under the right circumstances. They just run cooler because they are only 25% active.
  •   4164 Ram x 24, Plus 4116 to 4164 Adaptor

Faulty linear power supply dropping the +5V dc line

  • Important- Spec sheets for 4116 and 4164 RAM indicate an operating range of 4.5 to 5.5vDC.  When measuring voltage, measure directly at the pins on the RAM chips.  There can be over .5v drop between the power supplies 5 volts and when it arrives at the RAM chips.  I personally run a machine at about 5.1vDC at the RAM chips.
  • BEST SOLUTION- Search the KLOV forums for DOKERT, who is fabulous at rebuilding Williams Linear power supplies with a 5 volt adjustment pot.
  • Switching power supplies can be used but you will deal with CMOS memory getting reset for the high scores upon turning machine off or someone getting the high score. Has to do with the quickness the voltage drops on a switching power supply. See Robotron Power Supply Conversion Kit from ArcadeShop (my own experience is that the Switcher voltages vary day to day depending on conditions so you have to check the 5v before gameplay each day or week.)
  • Regarding high score table getting messed up- From yellowdog on KLOV forums-  If the bit rot caused by the CPU hosing the CMOS is not bad enough, it won’t cause the reset on the next power up, but all it takes is a few altered bytes in the CMOS to cause issues with the high score table. You can get the same effect with a linear power supply if you flip the switch on then off then on real quick. In that case, the big cap didn’t have a chance to charge up and so the +5V dropped as fast as the +12V unregulated. The write protect circuit won’t kick in quickly enough to protect the CMOS.
  • this suggestion from KLOV may work but I have never tried it:  Install a 4700uf 25v capacitor across the 5 volt and ground terminals.

Williams boards like a Linear power supply!!!!!- another reiteration from Yellowdog (Feb 2013) – Youtube vid of Ken

  • The 4700 mfd cap on the regulated 12V is a ripple filter. The 18000 mfd cap is there to hold the +5V line high while the unregulated 12v drops. This is to allow the CMOS memory protect circuit time to kick in when the power gets turned off.
  • All 68xx chips from the 6800 to the 6809 have a bug that causes them to write random values into memory during the period when the voltage drops below 4v until it is too low to operate. If that memory address is ROM or dynamic RAM, no problem. If it is CMOS that is not write protected, bye bye highscore, bookkeeping, and/or game settings. Williams engineers found this with the 6800s used for pins. Their solution was to use a sensing circuit to detect when the +12V unregulated voltage drops and to protect the CMOS from writes at that time. Meanwhile the 18K cap is acting like a batteryto keep the voltage up for those few milliseconds until the memory protect circuit kicks in.
  • A switcher does not have that additonal reservoir of power so when the +12V goes down, so does the +5V and the CPU goesspraying garbage into memory.  Right across your CMOS if you are not lucky.
  • That is the basis for not putting switchers into Williams classic games. Moon Patrol, go for it. That is an IREM board and doesn’t use CMOS anyway. MotoRace USA and Make Trax same thing. Aeroboto, 1942, NARC, SmashTV, not a problem. Defender, Stargate, Robotron, Joust, Bubbles, Blaster, Sinistar, Mystic Marathon, Joust 2, Inferno, Turkey Shoot all should be run on the old linear power supplies or you will be losing setting, high scores and bookkeeping. Not every time, but often enough to be a pain.

Fresh batteries on CPU board or it is suggested to convert to lithium battery.

  • per Yellowdog- AA batteries have alkali, not acid. But the “out-gassing” as they age is lighter than air, it floats up onto chips and causes corrosion.  Boards aren’t actually damaged by “acid leaking” as is commonly stated

Faulty ribbon cable connector between Rom board and CPU.

Dirty/corroded connector pins and chip legs.

  • Work in a static free environment, preferably with a ground strap on your arm.
  • Note orientation of chip before removing so it will be replaced correctly later
  • Be careful when gently prying a chip loose
  • Use a very mild abrasive to shine up the legs
  • Be careful when gently re-seating chips so as not to bend or break delicate legs
  • Cleaning the 2 special video chips on the ROM board have fixed the problem with colored “snow” appearing on the screen during gameplay.

Does playing Robotron on Difficulty 10 cause more strain on the hardware?

  • per Larry DeMar, Aug 2013- on a properly functioning board set, setting to level 10 is not more stressful. Buss transactions are running at full speed at any level setting. If the game needs to move more data than time permits, then things slow down, but there’s no extra strain on the HW.
  • …”other than the sticks getting yanked harder” – Ken House, Aug 2013

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