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Spent some time going from a pile of Atari System 2 boards I accumulated over the years as I had 720 in the shop that I was working on.  I didn't have any experience with these boards, but figured some had to be easy fixes and actually most of them were things like damaged traces or a bad socket, was surpised how many I got running. Here's some of the repairs, look out for broken crystals as well, I've seen them a few times on the video boards as they stand upright and get knocked off easily.

System 2 boards include 720, Paperboy, APB, Championship Sprint and Super Sprint, from what I've read they can be converted back and forth to some degree by swapping roms as well as the Atari Slapstic (security chip). Haven't tried it yet, but they CPU boards all look identical. I believe there were two versions of the video boards.  Repair logs follow, enjoy.

Atari System 2 Repair Log

Super Sprint CPU (12/8/17) – Board booted to garbage on the screen, clock signal looked good, reset signal was low (normal) and data lines were moving. Checked program roms and ram, but they tested good in another boardset, which I expected. Was puzzled on this one as it seemed to be behaving normally based on other boards I looked at it.  After some probing around found that 14.318 crystal had a broken leg, replaced the crystal and boardset booted fine.

Super Sprint CPU (12/7/17) – Board booted to garbage on the screen, clock signal looked good, but board was watchdogging.  Checked program roms and ram, but they tested good in another boardset.  Pressing on the TII processor during boot-up got the board to show signs of life.  Replaced processor socket and board played fine.

Paperboy CPU (12/6/17) – Nothing on screen, just some white raster.  Quick inspection showed some traces that were scratched.  None were cut, but two were smashed together and shorted. Cleaned up the area, retested the board but still nothing. Clock signal looked good, reset line was watchdogging.  Swapped program roms and rams into known working board to find bad 6116 at 6P.  Board now boots up and plays but has a sound issue.

Self tested reported bad rom at 2D, replaced it but sounds were still off, but no longer reporting that error. Started swapping sound ICs and found bad YM3012 on row 8. Replacing that fixed the problem.  Rom error 2D popped back during testing, replaced socket and it is started working again.

Paperboy Video (12/7/17) –  Board booted with video issues. Swapping roms into known working board and found rom at 6T to be bad. Burned new rom to fix the problem.

Paperboy Video (12/7/17) –  Lines in the “paperboy graphic” on the newspaper screen.  Pressing on roms showed that it went away when I pressed on one.  Removed rom, cleaned legs and reinstall to fix the problem (forget which rom it was).

Paperboy CPU (12/6/17) – Nothing on screen, just some white raster.  Quick inspection showed some traces that were scratched.  None were cut, but two were smashed together and shorted. Cleaned up the area, retested the board and it came back to life.

Paperboy CPU (12/6/17) – Board booted with random specks of garbage on screen.  Removed T11 processor and reseated it, board came back to life.

APU CPU (12/6/17) – Board booted to garbage.  While checking program roms, noticed that two were in the swapped in the wrong location, moved them back to the proper location and the board booted fine.

I've mentioned it before that my board repair skills are decent, but not to the point where I can fix every board I come across. Centipede seems to be one of those boards that I either figure out and feel really good about my skills or spend a half day trying to fix one and ask myself why I even bother trying to fix them.  Here's are few repairs I made recently as well as some from way back. Enjoy!

One troubleshooting note on these, always put the game in test mode if it isn't working, ram failures are common and the self-test does a half-decent job of telling you what ram is bad.

Nothing on boot (1/18/18)

1. 12 mhz clock signal looked good, but no 6mhz clock on test point.
2. Replaced 74LS163 at P2 and the board booted right up.

Nothing on boot (5/30/17)

1. No clock signal, 2N3904 at Q1 was bad. Crystal was damaged as well, replaced the crystal.
2. Board boots but reports ram error, three beeps, K7 is bad?
3. Replaced 2101 at K7, board still beeping three times.
4. Removed and socketed three other rams that were replaced at one point but weren’t socketed, repair worked looked decent, but wasn’t taking any chances. I’ve seen traces damaged in the past from stuff like this.
5. Still beeping three times, further probing showed floating outputs at K7. Also discovered 2H signal at pin 117 on rams K7, L7 and M7 was missing.
6. Checked continuity from N7, not there, repaired broken trace (that I couldn’t see) to fix the problem.
7. Board now beeps ten times. Removed and replaced 2101 at N5 to fix the boardset.

Solid screen on boot (5/26/17)

1. Reset button wasn’t working, replaced it.
2. Reset signal was stuck low.
3. VBLANK was WATCHDOG was not pulsing
4. Outputs on P3 (1V, 2V, 4V and 8V) were dead, clock signal input was good. Replaced 74LS163 at P3 and got some random garbage on screen. Piggybacking this chip did the same thing )showed garbage on the screen).
5. Board is now watchdogging.
6. Board passes long ram test on 2114 program ram using Fluke 9010a.
7. Program Rom 310 at J1 tests bad using Fluke 9010a, install a new program rom and board is now running.
8. During testing board started acting up, blank screen on boot sometimes, random garbage. Pressing on program roms and 6502 helped. Replaced sockets on 6502 and program roms and board is all better again.

Blue Screen (4/19/17) – Clean boardset that booted to a blue screen and that was about it. Swapped 6502, no change, put game into test mode and it beeped twice, indicated bad 2114 ram at F2. Removed, socketed and installed working 2114 ram to fix the boardset.

Plays, minor Video Issues (4/19/17) – I didn’t even realize the game had an issue until I played a game. Some of the centipede graphics were jumpy and other minor issues. Test mode reported a bad 2101 ram at L5 (six beeps), replaced this ram to fix the problem.

Plays, but Garbage Letters on Screen (2/28/12) –  Put game in test mode and it reported  Ram K7, replaced this and it then reported Ram M7 bad. It looked like M7 was already replaced (but not socketed).  Removed M7, installed socket, fixed broken trace from prior repair and put a new 2101 Ram and the board worked.

Plays, but Garbage Letters on Screen (2/29/12) –  Put game in test mode and it reported bad Ram K7, replaced this and it then reported Ram L5 bad.  Replaced Ram L5 and the board came up fine.

Video Issues, Zeros on Screen, No Sound (2/28/12) – Game would play, but there were zeros on the first screen. Reseating the character roms and the problem went away.  There was still no sound, checked around LM324 amp and found that the output was dead (input was dead too, but I assume the LM324 was causing that).  Replaced LM324 and sound came back.

No Sound (2/29/12) – Didn’t even bother troubleshooting, just replaced LM324 amp and the problem was fixed.

Garbage on Screen (2/29/12) – Board booted with some random characters on screen.  Tried test mode, but realized test switch was stuck on, replaced test switch, still garbage, nothing from test mode.  Watchdog was barking, tried disabling and test mode, but nothing. Swapped out four program roms (307-310) and the game came up with no background graphics.  Tried test mode and it reported a bad Pokey at C3 and bad ER-2055 IC. Replaced both of these and the board worked fine.

Spent some time going through the box of broken Pac-Man / Ms. Pac boards we've got kicking around the shop.  Seems like some Pac fixes are very straight forward, others I really struggle with and throw them back in the box. I think part of the problem is the how the boards were stored, some were thrown in a box, might have a scratch or two or some rust some ICs.

These days I tend to only work on cleaner boards, ones that haven't had prior repairs as sometimes the prior repair is botched and makes troubleshooting a PITA. Anyway a few tips for Pac repairs:

• Check out the repair logs, there are quite a bit of repairs out there as well as some good resources on repairing these boards, I'm too lazy right now to look them, Google is your friend.
• Check out the two original Midway Pac-man Advance Troubleshooting Manuals, again Google is your friend.
• As always, inspect the board for damage and other prior repairs.

Here's my basic Pac-Man repair procedure, at the last the beginning, the Midway manuals have additional steps:

Pac-Man / Ms. Pac-Man Board Repair Procedure

1. See Pac-Man Troubleshooting Manual.
2. Always use known working satellite boards, usually replace the sockets for the satellite boards right away as they tend to fail.
3. Always use known working roms on main board. I usually just remove the original proms and burn new 2532 eproms.  For Ms. Pac-Man, make sure 2532 roms at row 6 are 45ns or faster.
4. Check Ms. Pac-Man ribbon cable, they go bad often.
5. Test for voltage on large caps, should be 8.0 VDC on these. Test for 5 VDC on boardset.
6. Check for clock signals at Z-80 and other test point (per manual).
7. Make sure reset signal at Z-80 is high.

After this I go into using the Fluke 9010a to check that the program roms and program rams are working. After that I usually rely on prior repair logs to narrow the problem down if I don't see anything myself.  Some of my repairs from over the years, I don't usually note as many bad program roms anymore as I usually replace them first as preventative maintenance, hope this helps:

No Video, Deadish (3/28/17) – Board had fresh set of program roms installed, fairly clean boardset.  Voltage was 6.2 VDC on chips, turns out Q6 was shorted together on the back of the board as two traces were touching each other. Replaced Q6 and voltage was back at 5.05 VDC.  Clock and reset line checked out okay, used Fluke 9010a to test Roms and Rams, no problems.  Noticed reset line was not going low when hit the push button switch near the amplifier.  Replacing 74LS161 at 9C fixed this problem, but no change.  Visual inspection showed that 4F was installed backwards, replaced it with a known working Prom and the board fired up.

Board booted to Garbage, pretty much all “P” on the screen with other garbage graphics (3/28/17) – Board had fresh set of program roms installed already, replaced the sockets on the Z-80 and V-Ram board, replaced the Z-80 socket for the heck of it.  

Roms checked out okay on Fluke 9010a, all 2114 ram tests failed. Swapped rams and found 4R to be bad.  Replaced it and board was much closer, playing with wider horizontal red lines across most of the screen (except top and bottom).  Research of other repairs pointed to 2125 rams at 2A to 2D, piggybacked 2D and the problem cleared up. Installed new socket and 2125 ram at 2D to fix the problem.

Game Booted, but Everything was Super Fast, Not Working 100% (3/24/17) – Board looked fairly close to working, it booted up, but attract mode was moving really fast, game didn’t really play when you started, but it was close.  Maze was being redrawn very slowly during game mode.  Checked roms and with 2114 with Fluke 9010a just to be sure (didn’t think they were the problem) and they were fine.  Used Two Bit Diagnostic tool and the board didn’t pass the Interrupt test. Swapped at 74LS74 at 8C as it was already socketed and it fixed the problem.

Slight Hum Bar, Doesn’t work with Jamma Adapter (3/22/17) – Kind of an odd one, board had a very minor vertical hum bar.  Also, would not boot on a Jamma test rig (DC voltage was at 2.3 VDC), only on a original AC harness.  Replaced big filter caps, D6, D7 and D8, voltage regulator and a few other electrolytic caps, but no change.  Turned out Q6 on the heat sink was bad, replaced with a TIP31C and it booted perfectly on both test benches.

Sounds Missing/Scratchy (3/22/17) – Most sounds were missing or barely audible.  Bad prom at 3M.
When converted Pac-man to Ms. Pac-Man (11/24/14): The game comes up and plays fine, but then ghosts start flashing diagonally on the screen. It is not all of time and only when the maze screen is on. After it runs for a little while the ghosts start going through the maze blocks (not the on normal maze path). None of this happens when the board is left as Pac-Man. – Slow 2532 roms at row 5, use 45ns or faster.

Gobbling sounds and dying sounds off (11/18/14) – Bad prom at 3M.

Board would constantly try to boot (1/23/12) – Looked like the game was booting up, but it would never quite get there.  Reset line was going from high to low corresponding to the resetting at booting.  Started pressing on a few sockets and it seem to get further on booting, so I replaced a Z-80 daughterboard socket and rom socket, but no real change.  Finally noticed that if I left the game on for a couple of minutes it would get closer to booting and sometimes boot up fully and work.  Tested voltage on the two large caps and it was 7.0 VDC.  I replaced these caps and it the board booted fine.
Lesson learned: always test power supply voltage first.

Board comes up with “1” on top left corner of screen (3/19/12)  - This board was okay, then started acting up. I replaced a rom socket I thought was bad as well as the Z-80 and Z-80 daughter board sockets, but no luck.  Started pressing on the ribbon cable and the board would boot. Went through about 3 ribbon cables until I found a good one.
Lesson Learned: always check the ribbon cables.

Most Sounds Missing (3/19/12) – Most sounds were missing and those that did play seemed off.  Replaced 1N and socket at 1M as they looked pretty bad (rust). Could see sound signals going to 2M but not coming out, so I replaced 2M to no avail.  Noticed that 3M looked pretty rough and when I pulled it legs fell off of it.  Installed a new socket, but no change.  Checked signals going to 3M and were missing signals and pins 2 and 3, checked for continuity at 3P and 3N and didn’t get any. Ran two jumpers and the sounds came back.

Sounds Off Slightly (3/19/12)  - Everything played,  just seemed a little off. Replaced most caps in audio circuit to no avail. Reseated 1M and they came back.

Board had zeros all over the screen (3/19/12) – This board was working, but just came up with zeros. Self test didn’t show a ram error, but the troubleshooting guides suggested 4K was bad. Replaced 4K and it fixed the problem.

Boots to “1s” on the screen (3/19/12) – Self test didn’t change anything. Reset and clock lines looked okay, checked the bus with the 9010a and found data lines 2 and 7 stuck together.  Found a small socket tail shorting out the two data lines and fixed that problem.  Checked the program roms with the 9010a and found that 6E was bad. Board would now come up with an illegible ram error.  Tried the 9010a and it said ram 4K or 4N was bad.  Replaced 4K and the game now came up with graphics were off. Pulled graphic roms 5E and 5F and they were both bad. Burned new roms and the game works.

Game Plays but characters at bottom of the maze and only move horizontally (3/20/12) – actually a continuation of the last repair, I didn’t notice this until the next day. Game plays fine, but characters were offset low and moved only left and right.  Game seemed fine otherwise, started poking around in the final video output section and found that 1E pin 9 input was stuck high. Traced this back to 4C and found that pin 5 was stuck low. Replaced 4C (74LS00) and the problem was fixed.

Garbage on Screen (3/20/12) – Board was recently repaired as Pac-Man Plus but had Ms. Pac-Man roms and Proms installed. Suspected something with the roms as I knew it was recently working.  Connected 9010a and tested the roms and found 6E was reporting as bad. Pulled 6E and it verified okay with burner, but tried another rom just in case.  Problem was fixed, apparently the original 6E rom had some issue but still verified okay with my burner.

Nothing on Screen (3/20/12) – Board was noted as worked when complete. Installed new roms and it booted with nothing on screen. Connected 9010a and tested the roms and found 6E was reporting as bad. Installed another rom at 6E and the board booted but with horiztonal lines through characters across entire screen. Pushed on graphic roms at 5E and 5F and problem corrected itself so I installed new sockets.

Board would not come up after the new sockets were installed. After a few minutes I found the issue, when replacing the sockets a blob of solder fell out of the desoldering iron. I was able to clean it all up but broke a trace near 4E in the process. Repaired the trace and the board booted fine.

Nothing on Screen (5/16/12) – Tested for voltage and it wasn’t there and I smelled something burning.  Starting rebuilding the power supply for the heck of it and finally realized that two large diodes were worked on before and installed backwards. Replaced these and got my +5VDC back.  Boardset would then come with a out of sync screen, but coin up and play.  Sometimes the game would lock-in and play fine.  Started poking around and tapping on chips and found 3R (74LS161) was the problem.  It was replaced at one point and the socket and chip legs looked beat, so I replaced the socket and IC and the board worked.

White screen (5/17/12) –Board came up with a white screen, clock, reset, program roms and ram checked out okay.  Followed guide in troubleshooting manual and did not see any address signals at pins 5 and 6 at 4A.  Traced this back to 5A and noticed the IC was rusty.  Found about another 10 rusty ICs that I replaced until the board came up.  White screen was caused by bad IC at 3B (74LS157).

White background, red maze, blocks behind characters (5/17/12) – part of the rusty chip repair, bad IC at 5C.

No Sound (5/18/12) – Lost all sounds in testing.  Quick look found that 1L was rusty, so I just replaced that at the sound game back.

Two distorted characters on top right and one "zero” on top left (5/29/12) – Continuation of rusty chip repair.  This corresponds to a Ram 4M error, so I replaced that but not change. Also replaced the socket, no change.  Sometimes board would boot and play fine.  Finally realize Z-80 controller had about four more rusty ICs.

Pac-Man color off and some ghosts off (5/29/12) – broken trace at pin 15 of 2A.

Random Garbage on Screen (5/30/12) – Ms. Pac-Man board that booted with just some random characters and garbage graphics.  Starting swapping daughterboards and the Z-80 controller daughterboard was bad, had a number of rusty ICs.

Horizontal lines in characters (5/30/12) – Character rom at 5F had a bad socket.

Spent a bit of time going through some Donkey Kong and DK Jr. boards I've had sitting for a while.  Not included in these repairs are a few boards that had bad roms and/or bad rom sockets.   Boards with bad roms and/or a bad socket are fairly common in my experience and the first thing you should look at.  Also check the pots on the video boards as they tend to crack if the board has been banged around, the board will look out of sync if the pots are bad.

Donkey Kong Jr. CPU Boards

Jump Sound off Pitch, No Walk Sound (2/8/17) – This was a board I just fixed with the constantly thumping sound. Didn’t notice it had another sound issue until further play testing.  Replaced caps in jump section as well as some other caps in sound section, but no change.  Replacing 4020 IC at 6L fixed the problem, thanks to Scott Brasington for documenting this repair online.

Jump Sound Off Pitch (2/7/17) – Jump sound was out of pitch, just not right.  Replaced C24, C23 and C22 but no change.  Closer inspection showed pin 9 of 8L was never soldered properly through the board. The leg was bent and didn’t make it through the solder hole.  Looked like this was from the factory, the jump sound probably never worked properly. Was able to remove solder from hole, run a small metal lead through the hole and solder it to the leg to fix the problem.

Thump Sound Constantly On, No Music (2/7/17) – The “thump” sound from Donkey Kong jumping at the beginning of stage was constantly playing, no music was present. Initially thought this was a bad transistor as that seems to be common issue when sounds are stuck “on”.  All sound transistors tested good, swapped out the 8035 and sound rom, no change.  Recapped the sound section just in case, but no change.  Grabbed the logic probe and starting probing around before the 8035 and found pin 10 at 74LS04 at 6J was stuck low (it should have been high).  Replaced 74LS04 at 6J to fix the problem.

All Low Sounds (2/7/17) – Sounds were present, but very low.  Noticed R1 was burnt, replaced it, no change. Pulled Q1 and it tested bad, replacing C1815 at Q1 fixed the problem.

Donkey Kong CPU Boards

Garbage on Screen (1/31/17) – CPU boardset booted to garbage, went to pull Z-80 and test roms with Fluke 9010a.  Original Z-80 socket was replaced and the replacement socket didn’t look very high quality and poorly installed. Removed the socket, cleaned up the area as best I could and installed a new socket, board now works.

Garbage on Screen (1/31/17) – Fairly clean CPU boardset, complete, but boots to garbage.  Used Fluke 9010a to test roms and found program roms at 5C and 5F where bad.

One background sound during intro sequence out of pitch (after DK thumps) – recapped entire sound section, but no change.  Replaced LM724 at 8K and that fixed the problem.

Video Boards

Board had Mario Heads and Bottom on Screen (2/6/17) - Kind of an odd problem, it would boot up fine, after a couple minutes Mario's head and bottom would appear on the screen in the four corners (see picture).  Used some freeze spray to hit the chips and after spraying 2148 ram at 6R the picture would clear up again.  Replaced ram at 6R to fix the problem.

Sprites had horizontal lines (2/3/17) – Board looked close, but the sprites had horizontal lines running through them. Also a small horizontal line was on the title screen near the middle left hand-side.  Board had a fresh set of roms, swapping them into a working board, found rom at 7D to be bad.  Rom tested fine in burner, but didn’t work in the board.

No Sprites (5/18/12) – Board came up, but no sprites. Checked outputs at 3E and found a signal missing.  Replaced 74LS163 at 3E to fix the problem.  Thanks to Mike at Mike’s Arcade for this one, he had already documented the problem so it was easy to find.

Updated 6/11/18 - Added a repair

A few years ago I had a few Stratovox sets, managed to get half of them running fairly quickly by swapping boards or they were already working.  Dug out the other ones this week and picked up one online as well.  Fun game, I'm guessing way back when the speech feature was really impressive.  Anyway, most of these were fairly straightforward repairs, roms falling apart, or other simple things, but figured I'd share anyway.

CPU Board, Garbage on Screen (6/11/18) - Board booted to some garbage, was fairly clean.  Bad 2114 ram at E9.

UPDATE: Had a customer ask me to look at some of his boards and a couple I sold him that died.  Added these repairs.

Stratovox does require a reset signal to boot up, so you're using this on a Jamma test bench or other test bench, make sure you provide it or the board will boot to some vertical lines.

Game Board, No Red (4/28/17) - Board was working, died at customer's location.  Dead output at pin 3 of 74LS32 located 1H, the IC right before the red goes to the pinout.

CPU Board, Garbage on Screen (4/7/17) - Looked like it was trying to run, but would just show some graphics and sometimes some garbled sounds.  Z-80 and program roms checked out okay, swapping 2114 rams into a working board I found 9E to be bad, which fixed the problem.

CPU Board, Horizontal Lines (4/7/17) - Boards had horizontal lines on certain areas, again suspected a bad 4116 ram. They were already socketed, but the clearly the sockets were replaced a long time ago.  Pressing on the ram at 3E cleared things up. Replaced the socket to fix the problem.

CPU Board, Horizontal Lines (4/7/17) - Board booted with horizontal red lines, suspected a bad 4116 ram. Grounded output on 4116 rams and found lines went away when grounding ram at 1F. Replaced 4116 at 1F to fix the problem.

Game Board, Red Heavy (4/7/17) - Game board booted with good video but was very heavy with red, the background was red, not black.  Tried replaced 74LS174 at 1F and 74LS32 at 1H, but not change. Some further digging showed output at pin 10 of 5D was stuck high.  Replaced 74LS95 from 5D to fix the problem.

Game Board, Vertical Lines (4/6/17) - Game board booted but had horizontal lines, suspected a bad 4116 ram. Replace all eight of them, and picture improved but not perfect.  Output at pin 9 on 74LS157 at 4C was high, should have been pulsing, replaced 4C, but no change, replaced 5C as well, no change.  Went back to 4116 ram, found output at 3C (pin 14) was dead. Replaced 3C (again) and board worked, must have used a bad 4116 when I installed them initially.  

CPU Board Locked in Test Mode - Boardset came up with some numbers and characters on the screen. After checking the manual I realized it was booting in test mode.  Figured the test switch in put was stuck, found an IC on the CPU board (10F) that I thought was the cause. While replacing it I noticed a scratch in the traces near it.  Replacing the IC didn't change anything, checked continuity on the damage and three traces were bad. Jumpered them and board came back to life. Should have inspected the board closer initially.

CPU Board Booting to Garbage - Clock signal on Z-80 looked good, while checking the Z-80, I noticed the first program rom (LS01) was installed backwards.  Pulled it, tested it in a working board and rom was bad. Burned new LS01 rom and board worked.

CPU Board Not Working - Didn't even bother testing this one, started by pulled program roms after looking at some of the legs on these roms.  Three roms had very brittle legs, a couple broke off when pulling them. Burned new LS01, LS02, LS03 2716 roms, installed them and board worked.

Game Board, Speech Issues - This one was lacking speech or most of it. Noticed that I listened very closely I could hear a blurb or something that sounded like speech.  Pinched sound pot on the very corner of the board together while game board was on and speech got a little louder.  Replaced 100K speech pot and the speech came back loud and clear.