Problem:

• Board has messed up motion sprites, the sprites look complete but it looks like they are cut up into slices and the slices are in the wrong order, for example shooter looks liek the sides of the sprites are flipped on the wrong side. looks like this
  

Troubleshooting/diagnosis steps:

1. Replaced 74LS83 @ F6 and H6
2. Game works!

Problem:

• Motion Sprite are single color (white)

Troubleshooting/diagnosis steps:

1. Replaced 27LS201 @ A6
2. Game works!

Problem:

• Motion Sprite are messed up (sprite look like they are scrambled) looks something like this closeup from another board with the same problem
  
• Motion sprites appear multiple times in parrellel like this

Troubleshooting/diagnosis steps:

1. Replaced 74LS83 counter @ F6, that fixed the messed up sprite images leaving only the problem of multiple sprites displayed in parrell
2. Replaced 74LS83 counter @ H6, that fixed the multiple sprites
3. Noticed sound was really faint/messed up
4. Replaced LM324 @ K10
5. Game works!

Problem:

• Nothing on game board

Troubleshooting/diagnosis steps:

1. Board continuously resets
2. Check RAM and ROMs with Fluke 9010A, all OK
3. noticed screetching sound from game board
4. Pushed down at prom in sync section at P4 (as this seems to be a common problem). Notied game booted while I held it.
5. Removed old PROM socket and installed new one
6. game boots but has red lines though it like this
   
7. Pressed down on ROM sockets at H/J7 and F7 problem got better and worse
8. Removed both sockets and installed new sockets, reinserted PROMS
9. Game works!

Problem:

• Game is dead
• Owner of board sent 4 boards all said to be playing blind, he said they all played fine until he put them in a cabinet then one by one the cabinet broke the video, they all played blind. Onwer said he found his monitor chassis to be bad, after replacing it the cabinet stopped destroying game boards.

Troubleshooting/diagnosis steps:

1. No clock signal
2. touched crystal, made slight crackling noise when moved as if the case was broken, rattling.
3. Replaced crystal
4. Game comes up with the only color red where the white should be
5. Since owner stated that these batch of 4 boards (34,35,36,37) all worked before putting into the cabinet with the dead monitor and they all played blind or missing colors afterwards.. thought let's look at the last chip before the chassis in case the chassis was feedbing back stuff into the PCB board.
6. Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead.
7. Replaced LS07 @ A9
8. Game works!

Problem:

• Game plays blind
• Owner of board sent 4 boards all said to be playing blind, he said they all played fine until he put them in a cabinet then one by one the cabinet broke the video, they all played blind. Onwer said he found his monitor chassis to be bad, after replacing it the cabinet stopped destroying game boards.

Troubleshooting/diagnosis steps:

1. Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead.
2. Replaced LS07 @ A9
3. Game works!

Problem:

• Game plays blind
• Owner of board sent 4 boards all said to be playing blind, he said they all played fine until he put them in a cabinet then one by one the cabinet broke the video, they all played blind. Onwer said he found his monitor chassis to be bad, after replacing it the cabinet stopped destroying game boards.

Troubleshooting/diagnosis steps:

1. Replaced missing mylar capacitor near crystal
2. Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead.
3. Replaced LS07 @ A9
4. Game works!

Problem:

• Game only shows blue where white should be, no other color
• Owner of board sent 4 boards all said to be playing blind, he said they all played fine until he put them in a cabinet then one by one the cabinet broke the video, they all played blind. Onwer said he found his monitor chassis to be bad, after replacing it the cabinet stopped destroying game boards.

Troubleshooting/diagnosis steps:

1. Since this was the 4th in the same 30 minutes from the same batch of boards (#34, 35,36,37) just replaced LS07 @A9
2. Game works!

Problem:

Board is missing hex schmitt triggers @ EF/10 and EF/10 Board plays fine but motion sprites are all single color (wrong color)

Troubleshooting/diagnosis steps:

1. Found a bad 74LS174 @ C6. removed, added a socket and a new 74LS174
2. That solved the sprite color issues
3. Replaced missing MC14584 @ EF/10 and EF/11
4. Board plays but not saving high scores
5. Found bad 7815 @ VR2, replaced
6. Board works!

Problem:

Board works but is washed out in blue

Troubleshooting/diagnosis steps:

1. Looked at blue output lines, found bad 7407 @A9, replaced
2. Board works!

Problem:

Board works all sprites are missing

Troubleshooting/diagnosis steps:

1. Tested various chips in the motion circuitry
2. Found bad 74LS00 @ L8, replaced
3. Board works!

Problem:

Board works but colors are missing.

Troubleshooting/diagnosis steps:

1. Found bad 74LS07 @ A9, replaced
2. That fixed the color problem
3. But no sound..
4. Replaced LM324, fixed sound
5. Trackball control is not working
6. LED player 1 and 2 lights are constantly on
7. Still working on board

Problem:

Board is dead

Troubleshooting/diagnosis steps:

1. Checked reset line, stuck low
2. Noticed PROM @ p4 was missing, replaced
3. 1.5Mhz signal not correct, found bad 74LS163 @ N2 and N3, replaced
4. Got 1.5Mhz signal, though it looked unstable, wasn't sure if the chip pin was dirty or something
5. hooked up Fluke did a bus test got DB0 stuck low
6. Found bad 74LS245 @ E2, replaced
7. Did RAM long test of RAM range 0x0000 - 0x03FF, got BTS 0F error which indicates 2114 @ H2, replaced. Now RAM long 0x0000 - 0x03FF passes
8. Did RAM long test of video RAM 0x0400 - 0x07EF, bot BTS error 80, which indicates 2101 RAM @ K5, replaced, now RAM long 0x0400 - 0x07EF passes
9. Still no picture though and watchdog resetting the game, noticed 1.5Mhz is definitely not stable.
10. Found bad 74LS163 @ N3, replaced. 1.5Mhz signal is stable now and game is playing however sprites are missing
11. Found bad 74LS163 @ B5 (outputs stuck) replaced
12. Now shooter appears on lower part of screen, but then disappears
13. Found bad 74LS163 @ A5
14. Game works!

Problem:

• Board is dead
• Board is missing 12Mhz crystal

Troubleshooting/diagnosis steps:

1. Replaced crystal
2. Game works!

Problem:

• Board is dead
• Board is missing 12Mhz crystal
• Board is missing POKEY

Troubleshooting/diagnosis steps:

1. Replaced crystal
2. Replace POKEY
3. Game works!

Problem:

• Board has "weird graphic issues"
  

Troubleshooting/diagnosis steps:

1. Ran long Fluke RAM test 0x0000 -0x03FF - OK
2. Ran long Fluke RAM test on video RAM 0x0400 - 0x07BF - Pattern error @ 430 wrote CC got back C8, which should correspond to RAM N7
3. Put centipede in self test mode, got 9 beeps (indicating 2101 RAM at N7)
4. Pulled RAM N7, added socket
5. Ram issue still exists
6. Ran fluke RAM long test for RAM range 0x0430 - 0x43F, got back bits 0 and 2 tied
7. Looked closely at board, found small area where traces were smashed bridging 2 traces together
   
8. used x-acto knift to break up the bridge.
9. Game works!

Problem:

• Board plays blind

Troubleshooting/diagnosis steps:

1. powered up, noticed that LCD would not sync
2. coined up and started a game to verify it's coining up and starting
3. Used Oscilliscope to verify signal HSYNC and VSYNC - OK
4. Looked at schematics for video output section, tested !HSYNC and !VSYNC @ 74LS08 @ B7, OK
5. Checked output signal pin #3 on 74LS08 @ B7 - OK
6. checked input propogation to input pin #5 on 7407 @ A9 - OK
7. checked output signal on pin #6 on 7404 @ A9 - NONE
8. Removed 7407 @ A9, replaced with a socket and a new 74LS07
9. Game works!

Problem:

• Board is dead and monitor does not sync

Troubleshooting/diagnosis steps:

1. Verified clock at 1.5Mhz - OK
2. no sync on monitor, VSYNC line is dead, HSYNC line is OK
3. reset line stuck low
4. verified V frequencies at input to timing PROM @ P4, found all lines where good except 128V (pin #1) which was 120Hz rather than 60Hz
5. Traced back 128V signal to pin #11 on 74LS163 @ N3
6. Replaced 74LS163 @ N3
7. Game works!

Problem:

• Board just displays static garbage on screen, does not boot

Troubleshooting/diagnosis steps:

1. Probed reset line on CPU (pin #40) with oscilliscope, it's definitely resetting
2. Verified clock at 1.5Mhz on Ping #37 - OK
3. Looked at dirty looking POKEY, pulled POKEY
4. Game boots, with all mushrooms on left side (due to missing POKEY)
5. Replaced POKEY with a known good POKEY
6. Game works!

Problem:

• Board just displays purple screen, sometimes a flashing white sprite

Troubleshooting/diagnosis steps:

1. Flipped board over noticed two traces jumpered. Noticed that someone drilled a tiny hole through the board which cut to traces, repair was fine though, continuity OK
2. Tested +5V, OK
3. Pulled CPU and POKEY
4. Validated Pin 40 on CPU socket (reset) is transistioning and not stuck low
5. Valiadted Pin 37 (1.5Mhz Clock) on CPU is OK
6. Hooked up Fluke 9010A and did a bus test, OK
7. Did a LONG RAM test on scractchpad RAMS (2114s) in range 0x0000 - 0x03FF - OK, was surprised
8. Pulled ROMS out and tested, found 3 BAD ROMS (wierd... very unusual)
9. Inserted known good ROMS, game came up but had "issues"
   

   
   Sometimes the screen issues would change, especially if the board is moved. This usually means a loose connection somewhere or a bad solder job

10. Tried to put game into test mode, but just got a white screen and a single character in the bottom left of the screen.
11. flipped board over and found K5 was resoldered... horribly. Lots of damange.
    

    

12. Tried to fix traces and put in new socket normally but damage was so bad could not get a clean solder job done.
13. Had to ensure the socket was "lifted" off the board a bit to avoid solder blobs and to be able to verify connectivity and no bridged traced afterwards
14. Put in new 2101 RAM in socket
15. Game works!

Problem:

• mushrooms are lined up on left side, no sound

Troubleshooting/diagnosis steps:

1. Mushrooms being on the left side is a sign of a bad POKEY, missing sound is also a sign of a bad POKEY, replace POKEY!
2. Mushrooms are ok and sound is back, but test mode gives 8 beeps
3. Noticed RAM and sockets are missing for N5 and M5, replaced
4. Game works!

Problem:

• Games does not boot, just displays this screen (which I've never seen anything like before on a Centipede!

Troubleshooting/diagnosis steps:

1. Check reset line on CPU (pin 40 on CPU), it's transistining, so the watchdog is firing reseting the system. (rules out a stuck low reset, and tells me the reset and supporting circuitry is OK
2. CPU clock (pin 37) is good at 1.5Mhz
3. noticed RAMS at M5, N5, M6 and N7 were missing, sockets were replaced on M5 and N5, sockets were missing on M7 and N7.
4. Replaced missing sockets and installed missing 2101 RAMS
5. Still not working
6. Did a Fluke LONG RAM test for memory range 0x0000 - 0x03FF (scratchpad RAM) gave BTS error C0, noticed the corresponding 2114 had been socketed and replaced. Tried a new 2114 RAM
7. Fluke test 0x0000 - 0x03FFF OK
8. Did fuly RAM test on video RAM (0x0400 - 0x07EF) - OK
9. Game booting but getting thick lines through some things, missing some stuff near lines and random colors on lines
   
10. Probed around the video output circuitry, using logic comparitor found that a 74LS157 @ J8 seemed bad, used oscilliscope to find all outputs except 1 are stuck high
11. desoldered chip, chip was cracked and 2 legs fell off, accidentlly pulled up a trace while removing
12. Fixed broken trace, installed socket and installed new 74LS157
13. Lines disappeared, but tiles and sprites had wierd artifacts
    
14. Only thing I could think of was a ROM issue, verified graphics ROMS OK
15. after probing around decided to check for physical damage or briged traces, found that in my trace repair I forgot to cut off one end of the jumper and it was touchign some pins on the replaced 74LS157 @ J8 (which is feed from the ROMs).
16. Removed excess jumper wire
17. Game works!

Problem:

• Games does not boot,
• LCD on test bench is not syncing

Troubleshooting/diagnosis steps:

1. Checked watchdog (pin #40 on CPU) it's transitioning
2. No LCD sync is usually a SYNC issue, checked the CPU clock on pin #37 of the CPU, no clock (stuck high)
3. Tested each output of 74LS163 at P2 (first of the H counter chips) - OK
4. Moved to next counter in the Horizontal circuit, N2, first output tested (pin #14 is dead) replaced
5. Game boots, however after a while lost mushrooms and then POKEY tested bad in self test.
6. Pulled the POKEY socket, and installed a new socket
7. Mushrooms are back and POKEY working again, POKEY passes games self test
8. Game works!

Problem:

• Game boots but overwhelming green on the screen
  

Troubleshooting/diagnosis steps:

1. A8 read bad and looked OK whtn comparitor was no, replace no change
2. C8 (72LS289) went normal when o-scope probe was on pin #7 (green output) swapped, no change swapped, no change
3. green output is wierd, always 1/2 high (relative to ground)
4. zooming in a bit in o-scope timing, there is a clean 6Mhz signal on the green output!
5. 6mhz singal in input pin #1, which is feed from E8 pin #9
6. this is being feed from area0 input pin #12 on E8
7. traced input of pin #12 on E8 to to bad 74S74 @ F9
8. replaced 74S74 with 74LS74

Problem:

• Game boots and seems to play but shooter is WAY too high on the screen
• and shots are coming from below shooter!
• 8 beeps during self test

Troubleshooting/diagnosis steps:

1. RAM check 0x0000 - 0x03FF ok
2. RAM check 0x0400 - 0x073f - BTS 0x80 @ 0x7A0
3. replaced M5 - OK - 23 minutes from start to finish

Problem:

• Game does not play
• Crystal is visibly missing

Troubleshooting/diagnosis steps:

1. upon further inspection there are more missing chips
   • C8
   • H8
   • J8
   • K8
   • B1
   • E2
2. replaced crystal and missing chips, no sync
3. watchdog high, CPU looks OK
4. WATCHDOG SHOULD have been watchdogging
5. BUS test OK
6. RAM test 0x0000 - 0x03ff BTS 0x04 @ 2c8 this is H2 pin 11 -> pin #5 @ E2, this might be a bad
7. socket as the socket was replaced and damaged, verified connectivity between pins OK, removed 2114 @ H2 installed socket and replaced RAM, RAM test ok
8. RAM test 0x0400 - 0x07EF - OK
9. ROM test of D1, E1, H1, J1 failed
10. 307, 308, 310, 211, 212. tested fine out of circuit
11. 309 failed out of circuit, replaced
12. let's test the address selection circuit
13. chips reading OK though from the fluke on random addresses... odd
14. pulled POKEY and it seems to read OK, all EXCEPT J1 which is giving same sig as D1 was before when it was missing (all FF)
15. J2 and J3 are giving correct outputs when looping read on 0x3800 putting in another chip seems to give OK read, replaced ROM and game boots up
16. game works!
17. roms could use new sockets.
18. sometimes game would start with mushrooms on right side of screen and soiund messed up, pushing on pokey fixed
19. replaced pokey socket, seems to be OK
20. trackball was non-responsive, noted someone hacked up the chips @ F10 and F11, removed and replaced,
21. fixed burnt ground connector on edge connector
22. Game works!

Problem:

• Blue screen with a bunch of zeros

Troubleshooting/diagnosis steps:

1. reset pokey now game seems to play but everygthing is blue, and sometimes only things are miss colored and sometimes things are missing, seems to change each time I turn the game on or off, thinking video ram write signal probably is messed up.
   
2. ram check 0x0000 - 0x03ff - OK
3. ram check 0x0000 - 0x7EF BTS 0x00F @ 420 and OK till 0x460 that's M7, replaced - OK
4. found what looks like a small piece of tin foil on some chips underneath the board, removed
5. screen still blue , game not starting, sometimes there are tiles, sometimes not
6. pulled eproms to test
7. 307 - BFA2 - OK version 3
8. 308 - BAD (should be 14eb)
9. 309 - OK 600D - version 3
10. 310 - OK A93C - version 3
11. 211 - BAD
12. 212 - OK
13. replaced with single ROM board http://www.arcade-cabinets.com/board_hacks/CENTIPEDE-R, and replaced F7
14. game still not boot with normal CPU, verified CPU
15. POKEY is bad, replaced
16. replacing CPU socket
17. colors are way off, screen totally blue
18. r73 is missing
19. F9 pin 5 is dead, should be moving, well sometrimes moving, replaced no change
20. color rom at e8 not getting a write signal ever!
21. write is input #3 on c8 feed by 74ls32 @ a4
22. pin #3 on a4 was stuck low, replaced
23. game works!

Problem:

• Game boots but just static characters on the screen
  

Troubleshooting/diagnosis steps:

1. removed pokey, no change
2. Checked clock pin #37 on CPU, 1.5Mhz - OK
3. Checked watchdog pin #40 on CPU - watchdogging
4. Pulled CPU and put in another
5. Game works!

Problem:

• Trackball is messed up
• LED start lights stay lit always

Troubleshooting/diagnosis steps:

1. Trackball was all "wiggy"
2. Replaced 14584 @ E/F11, no chnage
3. replaced all 1uf caps in the trackball circuit, no change
4. replaced 74LS191 @ C11, no change
5. replaced 74LS74 @ D11, now trackball movement is stable but will never go down
6. replaced 74LS157 @ DE/11, trackball is now fixed
7. 74LS259 @M10 controls the LEDs, it is never getting it's !OUT signal on pin #14
8. traced !OUT back to pin #3 (!OUT) on 74LS32 is never going low, even though its inputs should be taking it low, replaced
9. game works!

Problem:

• Static garbage on screen

Troubleshooting/diagnosis steps:

1. getting a watchdog and a clock
2. ugg, customer had replaced the 5th socket (for single rom) with a machined socket and ruined it. Pins were not making contact and completly ripped out vias while removing... will try to fix that later.
3. RAM test 0x0000 - 0x03FF long, failed @ 0x40 with BTS 0x80 error, a few other addresses with BTS 80 that's F2
4. put in F7 into a ROM socket to do a ROM test to validate bus - OK
5. put in new socket and 2114 ram, still getting the BTS 0x80 errors
6. bit 8 is always low on address 40
7. doing a long ram test from 0 - 0x37 getting DCD error on bit A2
8. looks like bit 0x80 on data is messed up, not sure what's up here.
9. error doesn't actually look to be a DCD error for example 0x01 read 0x08 when read, but no other addresses read that from 0 - f even though it reports a DCD error, maybe try fluke with upgraded firmware
10. pulled 2114 @ H2, repladed, issue seems to have gone away.
11. Fluke RAM long 0x0000 - 0x03FF - OK
12. 2101 @ M5 is missing, replaced
13. Fluke RAM long @ 400 - 7EF
14. DCD error @400 bit 6 confirmed writing to 0x400 also writes to 0x440 and, writing to 0x440 writes to 0x400 at least both read back at both addresses
15. A6 to 2101 is generated from P7 74LS257, inputs to P7 look good as far as clock cycles, pulled 72ls257, tested ok,
16. replaced anyway, still getting DCD errors, argh address #6 (pin #2 is floating), traced back to damaged via in k1 pin #2, fixed - ram long now OK
17. replaced bad socket used single rom hack and modifing one of the other ROM sockets to take the single ROM
18. bad sound, replaced POKEY - OK
19. high score save doesn't work
20. swapped EAROM, - no change
21. replaced 555 timer - OK
22. put back original EAROM - OK
23. Game works!

Problem:

• High score circuit doesn't work

Troubleshooting/diagnosis steps:

1. Replaced ER2055 @ E5 with known good ER2055 - no change
2. replaced 555 timer @ B11 - no change
3. validated !write2 signal @ a4 #5 was good,
4. valided !EA ADDR @ a4 #4 went low at the end of a game
5. valided pin #6 @ a4 went low at the end of the game
6. Found 74LS175 @ E4 bad, replaced
7. Game works!

Problem:

• Game is not syncing usually.
• some times will sync, when it does picture colors are off, horizontal lines through the screen, the sprites are repeated 4 times across the screen, and the sprites are incorrect (look folded over themselves)

Troubleshooting/diagnosis steps:

1. pushed on PROM that handles Syncing (82S129 @ P4) when pushing on it sync got better or worse
2. replaced socket, sync issue fixed
3. Pushed on video ROMS at F7 and HJ7, lines went away
4. replaced sockets on video ROMS, problem fixed
5. Still having multiple sprites across the screen (4 shooters, 4 spiders etc), still having color issues, still having sprite object shape issues
6. The repeated sprites and messed up sprite shapes are most likely the 74LS83 counters @ F6 and H6
7. inputs to h6 and F6 seem OK
8. replaced E7 no change - put back original
9. A5 and B5 tested OK
10. C5 tested OK
11. L8 tested OK
12. pulled 74LS83 @ F6 - tested bad - replaced, seemed to fix the messed up sprites, but still multiples
13. pulled 74LS83 @ H6 - tested bad - replaced, fixed the multiple sprite problem
14. now the sprites are correctly formed and the correct number, however we still have color problem, colors are wrong, different colors each time the game starts? Color RAM write signal missing maybe?
    • not seeing a color RAM write on pin #3 of c8 this is controlled by 74LS32 (or gate) @ a4
    • got a write on a4 #1 !WRITE
    • got a write on a4 #2 !COLORRAM
    • not getting output #3 on a4 !COLORRAM WRITE when the inputs show there should be a low signal, chip tested bad in circuit - replaced and color issues fixed.
15. game works!

Problem:

• Load fast beeping, screen with green static garbage and horizontal lines moving down the screen
• Customer reports game worked before being moved and power supply fell on board smashing A1 and an voltage regulator

Troubleshooting/diagnosis steps:

1. pulled pokey - no change
2. checked clock - clock seems ok
3. fluke bus test ok
4. fluke RAM long 0x0000 - 0x03FF - RW err @ 0x0000 BTS 15
5. WHen I get a error in one ram bank I like to check against another to make sure it's not something in the circuitry that's common to them, let's do a fluke RAM test on video RAM
6. fluke long @ 0x0400 - 0x07EF - RW error @ 0x4000 BTS 15 - same error. There is no way these 4 different RAM chips (2 x 2114) and (2 x 2101) are all bad in the EXACT same way! something in common must be the problem.
7. got to be a decoding error or an error with the data bus
8. do looping read 0x0000 check pin #8 /CS on either 2114 RAM
9. got good CS signal
10. lets try clearing and setting the bits to see what happens
    • write @ 0x0000 value 0x00
    • read @ 0x0000 = 0x11
    • write @ 0x0000 value 0xFF
    • read @ 0x0000 = value FB
11. looks like we are settings bits probably a buffer error
12. let's try same @ 0x0400
    • w @ 0x0400 value 0x00
    • r @ 0x4000 = 0x11
    • w @ 0x0000 value 0xff
    • r @ 0x4000 = FB
13. both memories have the same issues common part in both circuits is E2, let's replace
14. chip tested bad out of circuit however replaced, same BTS issue same test with video RAM still same result.
15. taking out ROMs get a different RAM result, this tnme BTS 0x05 for 2114 range
16. trying video rom range same result
17. write tests of same values above are now showing write of 0x00 returns 0x01 and write of 0xFF returns 0xFB
18. need to do some ROM test to isolate issue to specific part of address or data bus or decoding.
19. next step is to examine the address selection circuitry
20. verified writes to 0x00 do not affect 0x0400, not an address selection issue
21. Started looking at the circuitry of the data signals that are messed up
22. pin #4 (Data Bus #3 (DB2)) on E2 is tied to ground
23. used capacitance meter to find short between DB2 and GND @ 74LS244 @ h5 74ls244 tesetd bad in circuit.
24. ok now getting BTS error 0x15 when ROM is in
25. getting BTS error 0x01 when rom is out, and getting low bit stuck high on all memory writes
26. found short between DB0 and +5v
27. used ESR meter found short @ 2114 @ H2 replaced with new socketed RAM - fixed BTS error
28. now getting RW error @ 0x1f0 BTS 80 error
29. trying RAM long @ 0x0400 - 0x7ef to isolate - RAM test OK
30. removed 2114 RAM @ F2 and replaced - RAM long @ 0x0000 - 0x03FF now OK
31. put ROMs back in an not getting BTS @ 14 @ 0000 - most have a address decoding error or a bad buffer
32. ok when only D1 is, get BTS 0x04 when E1 added, let's switch D1 and E1 see what happens
33. putting E1 into D1's slot get issues, E1 must be bad
34. put back D1, add FH1 - OK
35. put J1 in E1 - getting BTS 0x10 errors, must be bad
36. replaced E1 and J1 all ROMs in now
37. game now looks like it's booting but junk tiles can still see some of the test screen though
38. put in new 2 video ROMS, now have a blank screen
39. but test mode looks OK when pressed, actually ROM D1 reading bad
40. replaced D1 now game works
41. tested video ROM @ F7 211 out of circuit - OK
42. tested video ROM @ HJ7 out of circuit - bad
43. game boots however up/down movement on trackball does not - traced back signal verified square wave signal present when moved all the way to 74LS191 @ B11
44. replaced bad 74LS191
45. now game works except high score save does not
46. EAROM will not work if -30 is not present, to have that present all other voltages must be good as well as the 555 @ A11.
    • checked +15 - 15, +22, -22 voltages - OK
    • -30 is only at -15 will replace 555 @ A11
    • now -30 at -30v test point!
47. game works!

Problem: All sprites at the bottom row of the screen

Troubleshooting/diagnosis steps:

1. self test mode gives 9 beeps (that should be 2101 @ n7), pulled socketed and replaced, self check now passes.
2. still sprites only at the bottom of the screen, got to be a counter issue - found bad 74LS163 counter @ a5, in the horizontal motion object circuits (remember on centipede "vertical is horizontal".
3. Game boots and plays except backgrond thump thump and spider sounds are missing. Pulled, resocketed and repalced POKEY with known good pokey
4. While filling dips to get free play off, flipped language to german, then it would not go back, found DIP switch N9 was bad on switch #1, replaced.
5. Game works!

Problem: Video Issues, see the video here

Troubleshooting/diagnosis steps:

1. Video issues looks like noise on the RAM or bad ram, self test5 gives 4 beeps
2. RAM long 0x0000 - 0x03ff - ok
3. Ram long 0x0400 - 0x07ef - getting errors on high 4 bits of first RAM - which is k5
4. Replaced, game boots and passes self test mode.
5. High score circuit does not work
6. Replaced 555, no change
7. Replaced EAROM - high score now works
8. Game works!

Problem:

• Game does not work
• Customer board #1

Troubleshooting/diagnosis steps:

1. Reset line stuck low
2. Sync PROM in upside down
3. Put in good sync prom, now getting a game reset
4. Remove pokey no change
5. Check Voltage - OK
6. Check CPU clock - OK
7. Fluke 9010A Bus test - OK
8. RAM DCD error bit 5 confirmed by reading/write to 0x0 and 0x20
9. Address bit 5 is good to pin #13 of C1 maybe a little noisy, bad out pin #7 of C1
10. Removed 27LS244 buffer @ C1 still getting signal on pin #7 of C1 which should NOT happen, got to be a bridge
11. Pulled first game EPROM chip, found smashed traces underneath
12. Fixed, socketed location C1, put back original chip
13. RAM short 0x0000 - 0x03ff - OK game boots now
14. RAM long 0x0000 - 0x03FF - OK
15. RAM short 0x0400 - 04BF - OK
16. Sounds are not good, replace pokey with known good one - OK
17. Going to replace with a pulled pokey from one of the other boards
18. Trackball goes right on left or right movement check dir line, replaced F10, no change, put back original,
19. D9 pin #9 is stuck high, it should be moving when I move the trackball right/left
20. E11 pin 5 (input) is stuck high, output is high obviously
21. E11 comes from F10 6 (output) 5 input
22. F10 (which I just replaced, input 5 is good, no output on 6)
23. Tried replacing 75LS157 @ E11, no change, putting back original... What's going on?
24. Going to replace F11, it’s not even used but maybe schematics are wrong
25. Put in 74LS157 backwards, but in new one - no change
26. Removed 3.3Kohm resistor at R84, now only goes left. Will try replacing with 4.7Kohm Since signal input is very weak compared to other inputs (about 60%)
27. That worked! It’s very possible the issue is just my trackball unit, might not be putting out high enough output.
28. Game works!

Problem:

• Game works but missing all green
• Customer Board #2

Troubleshooting/diagnosis steps:

1. Socketed and replaced 7407 @ a9, no change, put back original chip
2. Green output is dead on pine #10 on a9
3. Looks like input to pin #13 on 74LS175 @ a8 is bad, chip tests good
4. Replaced, no change put back original
5. Moving to video RAM @ c8 replaced but no change put back original after accidentally screwing up mine
6. /COLORRAM is good
7. Found a broken trace, color has returned! Game works
8. Sounds and trackball work, but not high score circuit
9. -15V is not working replacing VR 7915 replaced that was not the issue,
10. Wait centipede doesn’t have a -12 on the jamma bench… argh
11. Replacing 555
12. That fixed it, game is good to go
13. Game works!

Problem:

• Board does not work, getting no video Sync
• Customer board #3

Troubleshooting/diagnosis steps:

1. Checked power - OK
2. Reset is stuck low
3. Checked CPU clock - OK
4. H sync circuits ok, P3 is dead, pulled and replaced
5. It was not p3, /vreset was stuck low
6. Bipolar @ p4 was bad, replaced with 82S129 adapter
7. Now game boots but has issues, graphics and resetting
   
   
8. Removing the POKEY fixes the resetting
9. RAM short with POKEY in @ 0x0000 - 0x03FF gives errors, remove pokey and it’s OK
10. Pulling POKEY
11. RAM long 0x0000 - 0x37BF - OK
12. RAM long 0x0400 - 0x07BF - OK
13. Put another POKEY in to verify that one is good, original POKEY bad, taking POKEY from another board, which is also bad (millipede) trying another board, another bad, trying again
14. Replaced 74LS157 @ k8 no change
15. Replaced bad socket @ d9
16. Ended up being a bad PROM @ HJ7 replaced
17. Game works

Problem:

• Board marked "BAD" with sticker over 2114 RAMS

Troubleshooting/diagnosis steps:

1. Missing PROM @ p4, replaced with my 82S{126,1129,131} bi-polar PROM replacement kit
2. 2114 RAMS are SUPER hot
3. Replaced, both were bad
4. game now boots and passes long RAMS test
5. Color is off, "white" is a shade of yellow
6. Some screens the sprites are missing parts (on the blue screens)
7. Looks like the blue is missing
8. A9 is the last stage in the color output circuit
9. blue input #1 to A9 (7407) is OK, but output on #2 is stuck low
10. Replaced 7407 with 74LS07 @ A9, board works!

Problem:

• Board works, but there is no sound

Troubleshooting/diagnosis steps:

1. Board was warped quite a bit in a convex curve
2. I could barely hear sound
3. Customer had previously replaced the LM324, but it looks like they might have damanged the underlying vias and traces.
4. I figured the customer burned the LM324 when installing it, so removed fixed traces and socketed and replaced
5. Still no sound
6. Pushed down on board and sometimes could get sound, was sure it had to be that previous repair, and I must have missed something in my attempt to fix.
7. Ends up my repair of the repair was fine, but C65 was actually broken in half, it was not visible but when removed the capacitor after ruling out everything else, the capacitor was split in two.
8. Game works!

Problem:

• Board will reset sporatically

Troubleshooting/diagnosis steps:

1. Board was warped quite a bit in a convex curve
2. Fluke RAM test 0x0000 - 0x7EF - OK
3. fell asleep, came back board is stuck in a static screen
4. Fluek RAM test gives BTS err 0xFF at various addresses
5. Game /RESET is transitioning constantly
6. Noticed if I pushed on the game or moved it it would start working again and resetting as I pushed more
7. Replaced PROM socket, CPU and POKEY socket, no change
8. pushed down on ROM, one "clicked"
9. Now it's not resetting anymore with phsyical strain
10. Removed all EPROMS, some were very dirty
11. Replaced sockets
12. Game no longer resetting
13. At some point (probably my fault, I think accidentally broke a chip all colors disappeared), game plays blind and monitor syncs, just no output at all.
14. Measured outputs of 74LS175 (last stage of color output), all output pins seems stuck low
15. Validated input pins where also not low, they had active data
16. Tested 74LS175 @ A8 in circuit with HP10529A, tested bad,
17. Replaced 74LS175 @ A8, game video returned to normal.
18. Game now boots and plays correct, however high score save is not working
19. Measured all voltage test points, all OK
20. Found a bad chip @ E4 (with HP 10529A logic comparitor), replaced
21. Now different symptoms, (incorrect readings)
22. Validated each input in the input to the EAROM, as much as possible
23. Just for fun replaced the Signetics 74LS244 that is a buffer to the EAROM data output, now I can save the data.
24. Unfortunately high scores would disappear after being off a while (though not off short periods of time)
25. Replaced the EAROM chip.
26. Game works!

Problem:

• Board does not work
• Repair video at

Troubleshooting/diagnosis steps:

1. Owner had noted that EPROM J1 (#310) had a broken pin, replaced
2. Voltage OK
3. Reset line is high, game is not resetting
4. CPU clock is ok at 1.5Mhz
5. Fluke BUS test - OK
6. Fluke RAM long for 2114 RAM range - 0x0 - 0x03FF - OK
7. Game boots, but has columns of "A" in various places,
   
   this indicates RAM Ranges 0x420 - 0x42F, 0x460 - 0x46F etc...
8. Fluke RAM long for 2101 video RAM range 0x400 - 0x7EF
   • as expected BTS error 01 on 0x420 - 0x42F, 0x460 - 0x46F, and 7 beeps on self test, this is 2101 RAM @ K5
   • Still have lots of junk on the screen and flashing "noise"
   • RAM long 0x400 - 0x7EF again, DCD errors on 0x400 - 0x40F etc, this indicates issues with RAM K7 or K5, both actually were bad, replaced
   Still have some noise on video display, cleaned video ROMs, that fixed it, re socketed the video ROM sockets
9. have sprite issues now where the sprites are cut up and inverted?
   
   I"ve seen this before, my notes say often 74LS83 @ F6 or H6, tested them in circuit they read bad (but they always seem to) tested the chips in the circuit that feed them and are feed from them, they are OK.
10. Replaced F6, that solved the issue
11. Game works!

Problem:

• Board works, sound does not though.

Troubleshooting/diagnosis steps:

1. Bad pokey, replaced
2. Game works

Problem:

• Board is dead, no sync on video
• Watch the repair video here

Troubleshooting/diagnosis steps:

1. Checked power - ok
2. Check /RESET - stuck low
3. Check CPU clock - none
4. Noticed transistor Q1 and Q3 by the clock, one is missing one is half knocked off. Replaced
5. Now the game is booting, but with sprite issues
   
   Note POKEY was removed when this picture was taken, that's why the mushrooms are all in a line
6. I literally just fixed a game with sprite issue like this yesterday, pulled 74LS83 @ F6 and replaced
7. Game works!

Problem:

• Customer said board did not work
• Worked for a few seconds on my test bench, then garbage

Troubleshooting/diagnosis steps:

1. Fluke bus test - OK
2. RAM long 0x0000 - 0x03FF bits 6 and 7 tied
3. RAM long 0x0400 - 0x07EF bits 6 and 7 tied
4. There is continuity between bit 6 and 7
5. This cannot be a issue with the RAMs themselves, not way all RAMs have this same issue in the RAMs, but be a bus error
6. FInd tiny piece of metal bridging traces, removed
7. Short is gone, RAM long is now OK on all ranges
8. boot boots but missing sprite foreground colors (eyes) 74S49 @ E9 doesn't seem to change, tests, bad, replaced with 74LS74, and that doesn't work, noise on screen. But back original
9. Testing C8 pin #14 (RAMA2) it's high all the time, however this is NORMAL (it will change if you go into test mode (color pallete write) Going to pull C8, looks like it's already be replaced so not too hopeful.
10. No change, put back original
11. Following chips backwards from C8 in Video Output Circuit
12. Tested D8 and e8 - OK
13. Tested 74LS32 @ C5, pin #3 showed bad in circuit, pulled and replaced
14. Game works!

Problem:

• Game is dead
• Game is missing 4 2101s in row 7
• No sync on video

Troubleshooting/diagnosis steps:

1. Replaced missing RAMS in row 7
2. Still nothing
3. No CPU clock and reset is stuck low
4. Noticed bipolar at P3 is missing, replaced
5. Now have static garbage on screen, still no cpu clock
6. CPU clock comes from 74LS244 @ B1 pin #18, with input at pin #2
7. Input on pin #2 is OK, all outputs are dead
8. NOticed that enable pins at #1 and #19 are floating.
9. Pulled 74LS244, no change
10. pulled R9 (pull up resistor that generates it, it was ok)
11. found that there was no continuity between the enable line and a point further up the wire
12. Found a cut in the trace, fixed
13. Game works

Problem:

Game works but is missing colors and all text

Troubleshooting/diagnosis steps:

1. 74S74 @ E9 looks like it has been previously pulled/resocketed and put back
2. pin #6 on e( is not outputing anything, open further inspection (when going into test mode, it actually does.
3. Pulled 27LS00 that feeds e9, no change
4. going backwards in circuit, tested C7 - OK
5. going backwards more, F9 was already tested
6. Tested j8, k8, f8, and h8 - OK
7. Only thing left really is j9 and h9, they both tested bad, but I think that's not a correct reading
8. J9 had floating output on it's output pin #13, H9 was fine
9. Pulled and replaced J9
10. Game works

Problem:

Game board boots but has graphics issues
Game fix video

Troubleshooting/diagnosis steps:

Problem:

Game board does not work at all

Troubleshooting/diagnosis steps:

Problem:

Game board does not work
Game is missing crystal
Game is missing video ROMS
Game is missing POKEY

Troubleshooting/diagnosis steps:

• Installed a crystal
• Installed video ROMS
• Installed a POKEY
• Game now boots but sprite graphics are showing green where they should be showing red (eyes of shooter, shot, spider eyes), looks like this
  
  Where it should look like this
  
  
• This is a problem with the motion video circuit since the tiles show red fine
• Found 74LS174 @ D6 has a bad output on pin #10
• Replaced D6, that fixed the video problem
• Game high scores saving is not working
• Tested voltage regulators - OK
• Tested pin #14 on EAROM, found it to be -14V it should be around -28V
• This is usually caused by a bad 555 at A11, found A11 is missing
• Installed 555 @ A11
• Game works!

Problem:

0's on half of the screen on bottom half

Troubleshooting/diagnosis steps:

1. replaced missing RAM at K7
2. Game works!

Problem:

Game Completely broken

Troubleshooting/diagnosis steps:

1. crystal missing, p4 mising, k7 mising, n5 missing, all roms missing, as well as CPU and pokey
2. replaced crystal
3. Bus test ok
4. RAM long 0 - 0x3ff - ok
5. no sync on LCD while runing, which makes sense, P4 is missing
6. replaced p4, now have sync
7. replaced video roms
8. found 1 row of pins on f7 were desoldered and vias stripped off
9. replaced missing rams, resoldered chips.
10. RAM long 0x400 - 0x7BF - BTS @ 0x410 0x0F that's L7 the one with 1/2 the pins desoldered and bad vias, removing and trying to fix
11. replaced ram long 0x400 - 7bf - OK
12. replacing missing code roms with single rom mod
13. OK with pokey
14. Game works!

Problem:

Game Completely broken

Troubleshooting/diagnosis steps:

1. missing pokey, and video RAMS
2. replaced video ram,
3. powered up, no sync
4. reset is stuck low
5. good 1.5mhz
6. N1 (74S04) (inverter) is low at #12 and high at #13
7. checking L2 #14 for signal, low (/VBLANK) going back to 74LS175 @ n4, #10 and #11 both are stuck (but opposites which is correct), input #12 is also stuck checkingt sync inputs @ all outputs (14, 13, 12, 11 are stuck), input clock is good
8. checking p3 outputs, all good pulling n3 since it seems to be bad (its a signetics), chip tested bad in tester
9. got a sync now, but blue screen
10. fluke bus test ok
11. ram 0x0000 - 0x03FF @ 0x0000 BTS 0xFF 0
12. unlikely both rams are bad, let's check 2101 range
13. ram long 0x400 - 0x7bf - ok
14. let's test the address selection for the rams by reading 0x0000 in a loop /cs is #8 /WE is pin #10
15. chips are getting /CS
16. check for /WE also getting there, we know buffer is OK since the video ram uses it, let's pull one of the RAM and replace to see what happens
17. replaced 2114 @ h2 now I'm only getting 0xF0 errors
18. replaced 2114 @ f2
19. Game works!

Problem:

Game Completely broken, LCD monitor doesn't sync

Troubleshooting/diagnosis steps:

1. Check /RESET on CPU (pin #40) - it is stuck low
2. inverter 74S04 input #13 high, #12 is low, going back
3. 74ls90 @ l2 pin #14 is low, that is /VBLANK
4. n4 ok, going to inputs to p4, all stuck low
5. Checking P3 and N3. both have good clock input, /VRESET low on both of those
6. Changed p4 no change, but this p4 in another board caused issues, so it's probably bad
7. put in new socket, still have the problem /vreset is stuck low so the counters do not work, but the counters control the chip that controls the chip that controls /vreset so I have a chicken in the egg situation
8. Pulling ht 74ls175 @ n4 so I can at least test the counters, externally it's ok
9. Both counters seem good put in a new 74ls175 @ n4 now I have sync
10. All outputs of p4 seem correct
11. Testing with fluke
12. Bus test ok, RAM long 0x0000 - 0x03FF - ok
13. Both video ROMs are missing
14. All 2101's missing, going to put in sockets and replace
15. replaced, game boots
16. RAM long 0x400 - 0x7BF - OK
17. Game works!

Problem:

Game Completely broken, have monitor sync, but just static yellow screen

Troubleshooting/diagnosis steps:

1. Sync is OK
2. Check /RESET on CPU, (pin #40) it is pulsing
3. bus test ok
4. Ram short 0x0 0x03ff, err @ 0x03 BTS 08
5. that's a 2114 RAM @ H2, replaced, game boots up
6. Going to do a ram check just incase
7. Ram long 0x0000 - 0x07BF - ok
8. game passes self test, and plays

Problem:

Game Completely broken, no sync on LCD monitor

Troubleshooting/diagnosis steps:

1. Board is missing one video ROM
2. Board is missing Rom @ JH/1
3. Board is missing PROM @ p4, replaced but no sync,
4. Checked /RESET on pin #40 of CPU, stuck low
5. Checked CPU clock (pin #37 on CPU) it is stuck low
6. no clock signal on N1 pin #2 or #1
7. I see Q3 has a leg broken will replace, it is not used in the clock circuit but is right next to the clock circuit
8. Q1 (used in initial clock circuit looks smashed, will replace)
9. replaced, now I have a 12Mhz clock, and sync
10. cpu clock is good, watchdog is going off
11. fluke bus test OK
12. RAM short 0x0 - 0x3ff ok
13. RAM short 0x400 - 0x7bf ok
14. Replacing missing video ROM at jh/1
15. roms d1, e1 and jh/1 are masked roms, will pull to test and label while ram long
16. 0x0000 - 0x7BF runs - ok
17. ROMS D1, E1, FH1 were all OK, version #3
18. Burned a new J1
19. Game boots and self test is OK
20. Game works!

Problem:

Game not working

Troubleshooting/diagnosis steps:

1. C8 missing, P4 missing A6 missing, CPU, POKEY, all socketed ROMs missing
2. Replaced p4, and C8, A6
3. Sync ok
4. Bus test ok
5. Ram long 0x0 - 0x3FF - ok
6. Ram long 0x400 - 0x7BF - @ 0x430 BTS err 0x01, thats N7, someone already replaced that one, it was socketed replaced it
7. Ram long 0x400 - 0x7BF ok

Problem:

• Game not working
• crystal is missing, PROM @ P4 is missing
• rams in row 7 have been removed, sockets installed
• all ROMS are missing and EAROM
• c8 is missing

  Troubleshooting/diagnosis steps:

  1. Replaced crystal and P4, now have sync on monitor
  2. Now getting just a plain white screen
  3. /reset is pulsing, CPU clock is at 1.5Mhz
  4. ram short 0x0 - 0x3ff BTS 0x02 @ 0x08 that's h2, I am replacing it
  5. getting BTS 0x40 @ 0x24 now, that's F2, replacing
  6. still getting BTS 0x40 errors, probably something with the socket replacements on the 2101, they are ugly.
  7. re-socketed and replaced missing RAMs in row 7
  8. Re-ran Fluke RAM short 0x0 - 0x3ff - now they are ok
  9. Fluke RAM long 0x400 - 0x7BF 0x FF
  10. RAMS getting read and write signal,
  11. Play field buffer @ J5 pin #1 and #11 look good, as well as inputs but all outputs are floating. (74LS373 (Signetics))
  12. Replaced 74LS373 @ J5, now no longer getting RAM errors
  13. Doing RAM long 0x0000 - 0x07BF - OK
  14. Screen is still all white, oh yes 82S25 @ c8 is missing... Replacing, no change
  15. Two ROMs read bad E1, and J1
  16. Odd two rams ceramics were cracked and one of the bad ones (not cracked, window was bulged and looks like something exploded inside), replacing
  17. Plain blue screen, board is watchdogging
  18. Pulled ROMS and re-verified and relabeled, all ok, put them back now it works, I must have originally labeled one wrong and put in the wrong place
  19. Game works

Problem:

• Game not working
• crystal is missing
• Both Video ROMs missing

  Troubleshooting/diagnosis steps:

  Video of repair
  1. Replaced crystal
  2. Replaced video ROMs
  3. Sprites messed up, looks basically the same as the board fix #31
     
     
  4. Replaced 74LS83 @ F6 and H6
  5. Sprite problem went away
  6. Sound was messed up, and mushrooms where missing
  7. Replaced POKEY
  8. Game works!

Problem:

• game boots but screen has a bunch of "O"'s on the screen
  
  

  Troubleshooting/diagnosis steps:

  Video of repair
  1. Replaced 2101 @ N7
  2. Mushrooms are messed up, replaced POKEY
  3. Mushrooms are OK
  4. While testing lost all sound, replaced LM324
  5. Sound is now back
  6. Game works!
  7. Game works!