Berzerk / Frenzy

Stern's Berzerk and Frenzy share the same board system.  Frenzy's ZPU board is different, but other than that the two games use the same boards.  In my experience these are very solid boards, not too many issues when going through them.  Some things to bear in mind while trying to resolve any issues:

  • As always, make sure you have a good power supply, good power connectors and power header pins on each board don't have any cracked solder joints (not too common).
  • Make sure you're ribbon cables are working, I've gotten to the point where I just toss my originals as I've seen too many bad ones. Replacement Bally MCR cables work in pinch (they have more pins, but can be used).
  • Check the ZPU board for corrosion / acid damage which is very common due to the original battery leaking.
  • Having a complete boardset to work from is key with a system like this as you can chase your tail a bit if you don't.  Swap any untested boards into the set one by one to narrow down problems.
  • To use a switching power supply, solder a jumper over CR26 on back of ZPU. This allows you to use modern power supply (has to due with unregulated +5 VDC from original power supply). Note this may lead to corrupted high scores, but it works for me when getting these boards running, however I usually don’t install batteries.
  • Self test beeping can be helpful in trying to determine which board is not working (see manual for more details).

ZPU Boards

ZPU, Booted to garbage (9/27/22)

  1. ZPU had some minor corrosion, but didn’t look like a lost cause.
  2. Replaced a few iffy transistors, resistors and reset button due to the corrosion. Cleaned up that area.
  3. Board boots to garbage, reset line is low.  Touching Base of Q3 causes board to boot and work fine.
  4. Replaced a few more resistors near Q3 (which was already replaced), including R39 and R38. Board now boots fine.

ZPU Booted fine, but game would start immediately (9/26/22)

  1. Board seemed fine, but game would immediately boot up. Suspect a smashed trace or something. I was wrong.
  2. Checked schematics, replaced 4A, as it had a little spot of corrosion on one leg, no change.
  3. Replaced 74LS155 at 7E, board still behaving the same way, but when I remove 7E it works normally.
  4. Suspected something on the other side of 7E, dipswitches looked fine. Replaced Memory Bookeeping Button on a whim.
  5. Board now works, the second time I’ve found a bad button that caused headaches. 

ZPU was working, died in bench testing (9/16/22)

  1. Was frustrating as I had it running fine. Quickly realized the reset was stuck low.
  2. Sometimes pressing on ribbon cables or other areas near the reset line would get it to boot.
  3. Replaced too many transistors that were a little suspect (but not awful).
  4. Spent a bit of time comparing resistor readings, everything looked good, still replacing a few.
  5. Took a step back, finally decided to remove the reset button, leg fell off and it was corroded. It was keeping the reset line low.
  6. New reset button and board works again.

ZPU Came up, then reset and freeze sometimes (9/17/14) – Suspected ribbon cables, but they seemed fine.  All socketed chips, roms, ram were tested okay.  Replaced the Z-80 socket as it seemed like the first logical step and that fixed the problem.

Board would sometimes beep once, sometimes seven times (9/16/14) – This was a clean Frenzy ZPU that seemed close to booting, replaced Z-80 socket and ram sockets as it seemed to get to the seven beeps more when I pressed on these chips, but no change. Checked roms with Fluke 9010a and they checked out fine.  Finally realized that the 6513/6514 ram jumper was incorrect for the ram I had on the board.  Moved the jumper per the manual and board booted right up.

Board did nothing on boot (9/16/14) – Another clean Frenzy ZPU that would do nothing on boot-up. Clock and reset signal looked good, swapped rams but no change.  Used Fluke 9010a and quickly realized that Roms 1 and 3 were swapped as the signatures it returned indicated this.  Swapped them back to their proper position and the board came up.

Nothing on boot (9/16/14) – Frenzy ZPU, checked reset and it was low.  There was some mild acid damage, but transistors Q1 and Q2 looked a bit rough. Replaced them and one leg fell apart in the process.  Cleaned up corrosion a bit and board booted up fine.

Nothing on boot (9/16/14) – Berzerk ZPU, checked reset and it was low.  There was some notable acid damage and I started with transistors Q1 and Q2 as they looked to be corroded. Cleaned up corrosion a bit, installed new 2N3904 transistors and the board booted up fine.

VFB-1000 Boards

Ram Error on boot (9/21/22)

  1. Suspected bad 4027 ram, swapped it out per self test, but no change.
  2. Pressing on the ram allowed the board to boot.
  3. Replaced ram socket to fix board.

1st Player Start Button not working (6/6/16) – resistors and cap looked good before the 74LS244 buffer at 5B. Replaced 5B and it fixed the problem.

Sound Boards

No sound (9/19/22)

  1. Tested outputs (pins 4, 14 and 15) at 4051 IC at C2, showed signs of sounds being produced.
  2. Replaced 2002 amplifier and sound now works.

Speech Boards

Speech Garbled at times (9/21/22) – board seemed close, some phrases were good, some were garbled.

  1. Checked the Speech synthesizer, it was good.
  2. Checked roms and 2C was bad, causing the issue.
  3. Burned new rom and installed and board works.