Disclaimer
Use this at your OWN risk, do NOT sue me if it breaks your board... if your doing this your board is probably already broken though ;)

Centipede Troubleshooting Information

Game Board #1

Problem: Game is dead No picture Tying to start in test mode provides no beeps Troubleshooting/dianosis steps: Using a logic probe, I noticed that the CPU wasn't doing anything, no address lines flipping, data lines are not flipping. Checked the clock line on 6502 with a logic probe... no transistions Replaced slightly dented original 8.2 Mhz crystal with a new 8.0 Mhz crystal - game now boots up but missing tiles, some tiles flipped upside down, ghosting on the screen, distored images Put game into test mode, 10 beeps Replaced 2101 SDRAM at N5 (according to the Centipede diagnostics page Game passes test mode.. missing tiles returned.. still some tile ghosting (spiders) and mushrooms have what looks like a period (.) in the bottom right corner, but looks promising, especially since it passed test mode and all the graphic tiles are back and game demo is running,problem gets less if you turn up the voltage higher but never completely goes away ground pin (pin 12) on F7 was not actually making contact with the ground line. (I damaged the trace when I replaced the ROM socket). solder a wire from pin 12 to ground, and that fixed the video problem

Game Board #2 1/14/2012

Problem: Game is dead No picture Tying to start in test mode provides no beeps Board missing crystal, broken cap, missing ROM Troubleshooting/dianosis steps: Replaced crystal Replaced broken cap (not needed just a TTL chip power filter cap) Replaced missing ROM Still didn't do anything on power up Using a logic probe, I noticed that the CPU wasn't doing anything, no address lines flipping, data lines are not flipping. Checked the clock signal with a logic probe... no transistions Used schematics to trace clock signal backward, found 74LS163 dead at position P2, replaced Game works

Game Board #3 3/31/2012
Problem: video unstable at normal voltage (+5V) Ground pad on edge connector looked like it was repaired before Some other pads had had been flowed with solder, making them significantly thicker Troubleshooting/dianosis steps: re-repair ground pad, used 18G wire to run bottom pad to top pad and expand connectivity on top pad unsoldered extra solder on other pads, flattened the pads out Game works

Game Board #4 4/4/2012

Problem: Power pads on edge completely blacked or missing Ground pad on edge connector was chared, pad next to it was disentigrating Board had excessive amounts of solder re-flowed onto the pads, creating an uneven surface Troubleshooting/dianosis steps: repair ground pad with copper foil tape, used 18G wire to run bottom pad to top pad and expand connectivity on top pad repair pad next to ground with copper foil tape removed excess solder on other pads Game works

Game Board #5 4/4/2012

Problem: One of the cleanest centipede boards I've ever seen... but... Game won't power on at all. Power supply shuts down immediately when plugged in Switching power supply will immediately shutdown after turning on Voltage regulator VR2 missing Cap C99 missing Troubleshooting/dianosis steps: Measured no resistance between ground and +5V. There is a short... but where is it? Hooked up computer power supply hard drive connector +5V and ground. Wired to +5V and ground on the centipede PCB test points Powered on computer supply. Immediately smoked 47LS153 at E8 Remove E8, replaced with a 16 pin socket and a new 74LS153 That fixed the short Replaced 7815 Voltage regulator at VR2 Game works!

Game Board #6 5/4/2012

Problem: cpu is half out of socket and pins bent, board very dirty, 7815 at VR2 has been badly replaced. Troubleshooting/dianosis steps: resocket CPU replace 7815 voltage regulator at VR2 do memory test, replace chip M5, memory issue still occurs use fluke 9010a, memory shows the most significant bit is bad. Trace lines to find that there is a piece of metal shorting MSB output with another line, remove and everythign works.

Game Board #7 5/4/2012

Problem: Game missing graphics ROM F7, missing voltage regulator at VR2, 12Mhz crystal is broken off, edge connector has had solder applied all over, 4 position DIP near NI1 is broken. Troubleshooting/dianosis steps: Pulled out other ROMS, all of them had missing pins Replaced ROMS Replaced 12Mhz crystal Replaced 7815 voltage regulator at VR2 Removed solder on edge connector pads Noted that it looks like IP at F6 was previously replaced booted board up, self test gives 3 beeps (K7), confirmed with Fluke, address 0x0400-0x040F (K7) show errors in high 4 bits (0111) which corresponds to 2101 at K7), replaced K7 Capacitor at c78 was looking rough, replaced board works Still need to replace 4 position dip switch

Game Board #8 5/4/2012

Problem: 12Mhz crystal is missing, all code ROMS missing (D1-J1), CPU missing, POKEY missing, EAROM chip missing, 8 pin dip switch @M9 broken Troubleshooting/dianosis steps: Replaced CPU Replaced POKEY Replaced ROMS Replaced 12Mhz crystal Powered on, LM324 at K10 smoked then power supply turned off... short circiut Removed LM324 board powered up, no sound, replaced LM324, sound is good run self test gives 8 beeps (M5), confirmed with Fluke, address 0x0420 (K7) show errors in high 4 bits which corresponds to 2101 at K5), replaced K5 board works Still need to replace 8 position dip switch

Game Board #9 11/42/2012
Problem: Game has messed up graphics, self test gives 10 beeps. (2101 at 5N) Troubleshooting/dianosis steps: Checked with Fluke 9010a memory tests, memory address 0x0430 has DCD error in address decode bit 9. Replaced 2101 at location 5N, fixed problem

Game Board #10 11/25/2012

Problem: Game has solid blue screen at boot Troubleshooting/dianosis steps: Tried putting into test mode, game shows pattern of "P"s about 1/2 of a column. Checked CPU with logic probe, it's resetting Clock is oscilating Hooked up to Fluke 9010a with 6502 POD. RAM 0x0000-03FF is BTS error FF all bits seem to be bad for all addresses, thinking data buffer chip. Checked Video RAM locations 0x0400-0x043F 0x0400-0x040F is good (RAM chips K5 (high 4 bits) and K7 (low 4 bits) 0x0410-0x041F has errors BTS F0 (all high bits), that is RAM chip L5 0x0420-0x042F is good (RAM chips M5 (high 4 bits) and M7 (low 4 bits) 0x0430-0x043F has errors BTS 10, that is RAM chip N5 Replaced 2101 at location L5 and N5, now all Video RAM addresses pass RAM long test Probes 2114 RAMs with a logic probe... some outputs were dead. Replaced both 2114s Game works!

Game Board #11 11/27/2012

Problem: Game has solid blue screen at boot Game is missing all ROMS and POKEY Game has very silent sound Troubleshooting/dianosis steps: Attached to Fluke 9010A - checked RAM, all RAM 0x0000-0x03FF showed bad, various errors on Video RAM addresses 0x0400-0x7FF Noted there seemed to be two memory ranges that gave consistant errors 0x0410 - 0x41F which corresponds to chip L5, replaced L5, no change Replaced data bus buffer chip on E2 as some pins seemed to be in a invalid state when probed with a logic probe... this cleared up some errors, now all memroy errors are consistant with DCD error bit 5 Checked pin correpsonding to bit 5 on C1 (address line buffer) it was stuck low. Replaced C1. Now all RAM checks work. Game boots up and passwd RAM and rom check, however in demo and play mode, only one line of motion is drawn... at bottom of screen Look as schematics... probe various chips in the horizontal motion section. LS163 counter at A5 seems to have bits set to low constantly. Cut power to that chip, errors remain the same. Replaced 74LS163 at A5. That fixed the graphics problems. Replaced LM324 at J10. Sounds now works. Everything works now!

Game Board #12 12/09/2012

Problem: Game doesn't work, no power LED Troubleshooting/dianosis steps: Checked +5V OK, replaced LED. LED works after replacement Game still as blank redish screen Getting Clock and can see ROM reads attempted Hooked up to Fluke 9010a, did long memory tests on RAM (0x0000 - 0x03FF) - OK Did RAM test on video RAM (0x0400 - - 0x07FF) OK Cleaned pins of very dirty CPU Replaced pulled PROMs put in known working test ROM at j1, game booted into test mode Replaced all PROMS except j1, test mode everything verified OK Tryed to replace j1 with original j1, no good Put back in working J1, game works fine

Game Board #13 12/09/2012
Problem: Game doesn't work. Troubleshooting/dianosis steps: Checked clock... permanently high Noticed 12Mhz crystal was ripped off, replaced crystal. gettting wierd stuff on screen reset and cleaned all ROM chips game comes on, but no foreground sprites, all mushrooms to one side, no sound Test mode says POKEY is bad Replaced POKEY Game works!

Game Board #14 12/09/2012

Problem: Game doesn't work. Troubleshooting/dianosis steps: Board looks prestine, but doesn't work Put in self test mode, got 2 beeps, which is RAM 2114 at F2. Verified with Fluke 9010a that there is an error in the high bits. Replaced, Now game comes to attract mode but there is garbage and some of the sprites flash to thing they are not supposed to be Put back in test mode, now get 9 beeps (2101 at N7) Replaced 2101 at N7, game now works!

Game Board #15 4/6/2013
Problem: Nothing on screen at all Troubleshooting/dianosis steps: Looked at board, noted the 12Mhz crystal was missing, replaced crystal Game works!

Game Board #16 5/8/2013

Problem: Nothing on screen at all Troubleshooting/dianosis steps: Looked at board, noted the 12Mhz crystal was missing, replaced crystal Game now boots up, and in test mode no error, however screen has red lines through it and all sprites looked at graphics ROM chip @ J1, pins looked like they might be bent up Pulled out ROM at @ J1, many pins where bent, some bent nearly in half Straightened pins and re-inserted Game works!

Game Board #17 8/29/2013

Problem: Game immediately starts playing when turned on, game is constantly shooting, and shots are no where near the shooter. random text on screen, after a few seconds the mushrooms will clear and the board will reset, all messed up. A movie of the issues which more clearly shows the issues is here Troubleshooting/dianosis steps: Looked at board, it is very clean Pulled the POKEY, no change, re-inserted POKEY Put the game in test mode, just a contant beeping Ran a RAM LONG test with the fluke on addresses 0x0000-0x07EF, got BTS errors on bit 80 starting at address 0x0000 and going up. removed F2 and H2, installed new socket and new 2114 RAM, issue was F2. Game works!

Game Board #18 10/28/2013
Problem: Game board has black screen Game is missing ROM D1 Troubleshooting/dianosis steps: Put game in test mode, it indicated that everything was OK except ROM @ D1 Pulled out the rom at E1, read it in ROM programmer, it's game version 3 Programmed a 2716 with D1 version 3 code Game works!

Game Board #19 12/14/2013

Problem: Game board has black screen, is not playing. Troubleshooting/dianosis steps: Noted smell of burning plastic, found LM324 was burning up, replaced. Game now as garbled screen, but does not work Tested RAM 0x0000 - 0x03FF got all BIT bad Tested Video RAM - 0x0400 - 0x07EF - OK Tested ROM - found ROM D1 and J1 were bad, replaced Since Video RAM and ROMS were OK went back into lookig at RAM issue. Validated address decoder circuitry looking for valid chip selects and write signals to 2114 RAM - OK Found outputs on LS245 @ E2 were strange, no valid states, replaced, no change The only thing besides the LS245 are the 2 2114 RAMs themselves, cut thep ower pin to each. Retested outputs of LS245 @ E2, now they look good Removeod both 2114 RAMs, socketed and replaced Fluke passes long RAM test Game works!

Game Board #20 3/15/2014
Problem: Game does nothing Troubleshooting/dianosis steps: Hooked up Fluke 9010A, got a pod timout error Noticed that 12Mhz crystal was missing, replaced game boots, but freezes when going into test mode Noted that the watchdog does not trigger even if CPU is removed or ROM removed found bad 74LS00 @ L8, replaced game works!

Game Board #21 3/15/2014
Problem: Game is dead Troubleshooting/dianosis steps: Noted Watchdog is stuck high Traced back timing circuits founda bad 74LS163 @ M2, replaced Game works!

Game Board #22 3/15/2014
Problem: Game is missing POKEY and 6502 Troubleshooting/dianosis steps: Installed POKEY and 6502 Game Works

Game Board #23 3/16/2014

Problem: Game is dead Game is missing a 2114 RAM Troubleshooting/dianosis steps: Testing +5 voltage, OK Plugged in Fluke 9010A, tried bus test, got POD timeout errors Checked the clock @ pin 40 of the CPU with Oscilliscope, got a reading of 3Mhz (twice what is should be) Found a bad 74LS163 @ P2 (counter for step down), replaced Clock is good Replaced 2114 RAM, all ram tests (0x0000 - 0x03FF (2114s) and 0x0400 - 0x07EF (2101s) pass) Game boots but colors are messed up Still working on game

Game Board #24 3/16/2014
Problem: Game is dead Troubleshooting/dianosis steps: Testing +5 voltage, OK Found watchdog was stuck low Using oscilliscope traced back timing circuits from the watchdog, found a bad 74LS163 @ N3, replaced Game works!

Game Board #25 4/29/2014

Problem: Game is dead, something like this on screen Troubleshooting/dianosis steps: Did Fluke RAM Long on 2114 RAM range (0x0000 - 0x03FF) OK Did Fluke RAM LONG on 2101 RAM range (0x0400 - 0x07EF) FAIL BTS 0xFF Tried a write to 0x0400 noted I did not get back what I wrote Did a read on 0x0400 in looping mode and noticed the results were chaning Wrote a 0x01 to 0x0400 which should turn the top right of the screen (or bottom left in a normal oriented cabinet) to A. it DID, even though the Fluke was not able to see it Tried writing differnt values to 0x400 and noticed they always displayed correctly on the screen, even thought they were being reported wrong back to the CPU/Fluke. This means that the data is being sent to the RAMs corretly and is being written correctly but the RAM reads are failing so that circuitry that goes from the RAM output back to the CPU must be bad. Looked at the schematics and saw the only chip that was in the datapath was as 74LS373 @ J5, removed it and replaced... but no change!!! Carefully examined the board, found a couple traces near N4 to be damaged. Used a multimeter in Ohmeter mode to validate that the traces were cut. Fixed the traces with some jumper wire. Game works!

Game Board #26 4/18/2014

Problem: Game is constantly resetting in wierd ways Troubleshooting/dianosis steps: Did Fluke RAM Long on 2114 RAM range (0x0000 - 0x03FF) most significant 4 bits failed in different ways at many addresses Replaced the 2114 RAM @ F2 Did a Fluke RAM Long test on the RAM ranges for 2101 (0x400 - 0x7EF), OK Fluke passed long test and booted Noticed that the game would start resetting in wierd ways again here is a video Noticed this happed when either of the 8 switch dip switch switches 4-8 were set to ON Replaced 74LS257 @ M8 Game works!

Game Board #27 4/19/2014

Problem: Game has nothing but garbage on screen Troubleshooting/dianosis steps: Did Fluke RAM Long on 2114 RAM range (0x0000 - 0x03FF) most significant 4 bits failed in different ways at many addresses Replaced the 2114 RAM @ F2 Reran the ROM Long test on 0x0000 - 0x03FF, OK Game now boots but is now showing this "double" screen self test indicated 9 beeps (2101 @ N7) Did a Fluke RAM Long test on the RAM ranges for 2101 (0x400 - 0x7EF), failed with RAM pattern error Did a RAM LONG from 0x0400 - 0x040F (OK) Did a RAM LONG from 0x0410 - 0x041F (OK) Did a RAM LONG from 0x0420 - 0x042F (OK) Did a RAM LONG from 0x0430 - 0x043F (got bits 0 and 2 tied) Noticed someone already replaced N7. Pulled socket in case someone made a solder blob Put in new socket and new 2101, still getting 0 and 2 tied Put back old 2101 Looked at video RAM circuit, bits 0 and 2 for that range lead to pin 13 on 74LS153 @ N6 and pin 3 @ 74LS153 @ M6. used multimeter to verify pin 13@N6 and pin 3@M6 were connected, they were Tracked circuits to where they the traces run close together and ran the multimeter probe lighty to knock off any metal fragments or squished together traces now RAMs are working, pass Centipedes built in self test as well as Flukes RAM longs test for 0x0400 - 0x07EF still getting the double screen though Looked at timing circuit/counters used oscope to validate P2, N2, When looking at M2 it was clear someone replaced this chip... badly pulled 74LS163 @ M2 noticed some damaged pads and traces Resocketed and put in a new 74LS163... still the same problem verified connectivity from pins on new socket to where they should go, found that pin 14 did not have connectivity (this pin had a damaged via/pad). removed solder and resoldered with a little more solder and a few more seconds of the soldering iron.. retested connectivity OK Game works!

Game Board #28 6/12/2014

Problem: Game boots but has garbage on screen... looks like this Was also getting "static/random red lines" on the screen (not visibile in picture) Troubleshooting/dianosis steps: Board was dirty covered in spots with something sticky and redish, washed off and cooked in oven to dry Found smashed traces near 2102's at row 7, used x-acto knife to seperate traces. That fixed the problem with the mushrooms that were "decayed" all PROMS rusty, PROM at F7 has some legs fall off, replaced ROM at F7 that fixed the random red lines/static. Cleaned off other PROMS Put in new sockets for video ROMs @ F7 and H/J7 powered on and put into self test mode, system gave 4 beeps, indicating bad RAM @ K5. Verified bad RAM with Fluke Long RAM test, got BTS error F0 @ 0x0400 which corresponds to RAM K5, replaced RAM. Put in self test mode again, system gave error code of 7 beeps which indicates RAM @ M7. Verified bad RAM with Fluke Long RAM test, got BTS error 03 @ 0x0420 which corresponds to RAM M7, replaced RAM. Game works!

Game Board #29 6/12/2014
Problem: Filler Page (board labeled ED) Troubleshooting/dianosis steps:

Game Board #30 6/15/2014

Problem: board shows just white screen Troubleshooting/dianosis steps: Noted board had no clock signal at clock test point Traced problem back to 74LS244 @ B1, input pin 2 had a good signal, but output pin 18 was stuck. Replaced 74LS244 @ B1, now got a good clock signal to test point Still got a white screen Did Fluke RAM long test 0x0000 - 0x03FF got BTS FF indicating both 2114s were bad. Wanted to verify, using fluke and read/write loops verified 2114s were both getting the correct chip select and write signals Did a RAM long check on the video RAM @ 0x0400 - 0x07EF, OK Did a ROM check, OK This verified most shared components of the memory signal. Pulled 2114s and replaced. Now fluke RAM long test @ 0x0000 - 0x03FF were OK Still got a white screen felt board for hot chips, found video memory82S25 @ C8 was burning hot. Pulled 82S25 @ C8 and replaced, now have tile/picture video, but no motion sprites! Found bad 74LS163 @ B5, replaced. Game works!

Game Board #31 6/16/2014
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/dianosis steps: Replaced 74LS83 @ F6 and H6 Game works!

6/16/2014
Problem: Motion Sprite are single color (white) Troubleshooting/dianosis steps: Replaced 27LS201 @ A6 Game works!

Game Board #32 6/16/2014

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/dianosis steps: Replaced 74LS83 counter @ F6, that fixed the messed up sprite images leaving only the problem of multiple sprites displayed in parrell Replaced 74LS83 counter @ H6, that fixed the multiple sprites Noticed sound was really faint/messed up Replaced LM324 @ K10 Game works!

Game Board #33 6/16/2014

Problem: Nothing on game board Troubleshooting/dianosis steps: Board continuously resets Check RAM and ROMs with Fluke 9010A, all OK noticed screetching sound from game board Pushed down at prom in sync section at P4 (as this seems to be a common problem). Notied game booted while I held it. Removed old PROM socket and installed new one game boots but has red lines though it like this Pressed down on ROM sockets at H/J7 and F7 problem got better and worse Removed both sockets and installed new sockets, reinserted PROMS Game works!

Game Board #34 7/29/2014

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/dianosis steps: No clock signal touched crystal, made slight crackling noise when moved as if the case was broken, rattling. Replaced crystal Game comes up with the only color red where the white should be 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. Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead. Replaced LS07 @ A9 Game works!

Game Board #35 7/29/2014

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/dianosis steps: Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead. Replaced LS07 @ A9 Game works!

Game Board #36 7/29/2014

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/dianosis steps: Replaced missing mylar capacitor near crystal Measured inputs vs outputs on 7407 @ A9 (last chip before monitor chassis) found outputs to be dead. Replaced LS07 @ A9 Game works!

Game Board #37 7/29/2014

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

Game Board #38 8/16/2014
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/dianosis steps: Found a bad 74LS174 @ C6. removed, added a socket and a new 74LS174 That solved the sprite color issues Replaced missing MC14584 @ EF/10 and EF/11 Board plays but not saving high scores Found bad 7815 @ VR2, replaced Board works!

Game Board #39 8/16/2014
Problem: Board works but is washed out in blue Troubleshooting/dianosis steps: Looked at blue output lines, found bad 7407 @A9, replaced Board works!

Game Board #40 8/16/2014
Problem: Board works all sprites are missing Troubleshooting/dianosis steps: Tested various chips in the motion circuitry Found bad 74LS00 @ L8, replaced Board works!

Game Board #41 8/16/2014
Problem: Board works but colors are missing. Troubleshooting/dianosis steps: Found bad 74LS07 @ A9, replaced That fixed the color problem But no sound.. Replaced LM324, fixed sound Trackball control is not working LED player 1 and 2 lights are constantly on Still working on board

Game Board #42 8/17/2014

Problem: Board is dead Troubleshooting/dianosis steps: Checked reset line, stuck low Noticed PROM @ p4 was missing, replaced 1.5Mhz signal not correct, found bad 74LS163 @ N2 and N3, replaced Got 1.5Mhz signal, though it looked unstable, wasn't sure if the chip pin was dirty or something hooked up Fluke did a bus test got DB0 stuck low Found bad 74LS245 @ E2, replaced Did RAM long test of RAM range 0x0000 - 0x03FF, got BTS 0F error which indicates 2114 @ H2, replaced. Now RAM long 0x0000 - 0x03FF passes 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 Still no picture though and watchdog resetting the game, noticed 1.5Mhz is definitely not stable. Found bad 74LS163 @ N3, replaced. 1.5Mhz signal is stable now and game is playing however sprites are missing Found bad 74LS163 @ B5 (outputs stuck) replaced Now shooter appears on lower part of screen, but then disappears Found bad 74LS163 @ A5 Game works!

Game Board #43 8/22/2014
Problem: Board is dead Board is missing 12Mhz crystal Troubleshooting/dianosis steps: Replaced crystal Game works!

Game Board #44 8/22/2014
Problem: Board is dead Board is missing 12Mhz crystal Board is missing POKEY Troubleshooting/dianosis steps: Replaced crystal Replace POKEY Game works!

Game Board #45 1/23/2015

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

Game Board #46 1/26/2015

Problem: Board plays blind Troubleshooting/dianosis steps: powered up, noticed that LCD would not sync coined up and started a game to verify it's coining up and starting Used Oscilliscope to verify signal HSYNC and VSYNC - OK Looked at schematics for video output section, tested !HSYNC and !VSYNC @ 74LS08 @ B7, OK Checked output signal pin #3 on 74LS08 @ B7 - OK checked input propogation to input pin #5 on 7407 @ A9 - OK checked output signal on pin #6 on 7404 @ A9 - NONE Removed 7407 @ A9, replaced with a socket and a new 74LS07 Game works!

Game Board #47 1/29/2015

Problem: Board is dead and monitor does not sync Troubleshooting/dianosis steps: Verified clock at 1.5Mhz - OK no sync on monitor, VSYNC line is dead, HSYNC line is OK reset line stuck low verified V frequencies at input to timing PROM @ P4, found all lines where good except 128V (pin #1) which was 120Hz rather than 60Hz Traced back 128V signal to pin #11 on 74LS163 @ N3 Replaced 74LS163 @ N3 Game works!

Game Board #48 2/28/2015
Problem: Board just displays static garbage on screen, does not boot Troubleshooting/dianosis steps: Probed reset line on CPU (pin #40) with oscilliscope, it's definitely resetting Verified clock at 1.5Mhz on Ping #37 - OK Looked at dirty looking POKEY, pulled POKEY Game boots, with all mushrooms on left side (due to missing POKEY) Replaced POKEY with a known good POKEY Game works!

Game Board #49 7/17/2015

Problem: Board just displays purple screen, sometimes a flashing white sprite Troubleshooting/dianosis steps: 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 Tested +5V, OK Pulled CPU and POKEY Validated Pin 40 on CPU socket (reset) is transistioning and not stuck low Valiadted Pin 37 (1.5Mhz Clock) on CPU is OK Hooked up Fluke 9010A and did a bus test, OK Did a LONG RAM test on scractchpad RAMS (2114s) in range 0x0000 - 0x03FF - OK, was surprised Pulled ROMS out and tested, found 3 BAD ROMS (wierd... very unusual) 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 Tried to put game into test mode, but just got a white screen and a single character in the bottom left of the screen. flipped board over and found K5 was resoldered... horribly. Lots of damange. Tried to fix traces and put in new socket normally but damage was so bad could not get a clean solder job done. 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 Put in new 2101 RAM in socket Game works!

Game Board #50 7/22/2015
Problem: mushrooms are lined up on left side, no sound Troubleshooting/dianosis steps: 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! Mushrooms are ok and sound is back, but test mode gives 8 beeps Noticed RAM and sockets are missing for N5 and M5, replaced Game works!

Game Board #51 7/22/2015

Problem: Games does not boot, just displays this screen (which I've never seen anything like before on a Centipede! Troubleshooting/dianosis steps: 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 CPU clock (pin 37) is good at 1.5Mhz noticed RAMS at M5, N5, M6 and N7 were missing, sockets were replaced on M5 and N5, sockets were missing on M7 and N7. Replaced missing sockets and installed missing 2101 RAMS Still not working 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 Fluke test 0x0000 - 0x03FFF OK Did fuly RAM test on video RAM (0x0400 - 0x07EF) - OK Game booting but getting thick lines through some things, missing some stuff near lines and random colors on lines 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 desoldered chip, chip was cracked and 2 legs fell off, accidentlly pulled up a trace while removing Fixed broken trace, installed socket and installed new 74LS157 Lines disappeared, but tiles and sprites had wierd artifacts Only thing I could think of was a ROM issue, verified graphics ROMS OK 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). Removed excess jumper wire Game works!

Game Board #52 12/18/2015

Problem: Games does not boot, LCD on test bench is not syncing Troubleshooting/dianosis steps: Checked watchdog (pin #40 on CPU) it's transitioning No LCD sync is usually a SYNC issue, checked the CPU clock on pin #37 of the CPU, no clock (stuck high) Tested each output of 74LS163 at P2 (first of the H counter chips) - OK Moved to next counter in the Horizontal circuit, N2, first output tested (pin #14 is dead) replaced Game boots, however after a while lost mushrooms and then POKEY tested bad in self test. Pulled the POKEY socket, and installed a new socket Mushrooms are back and POKEY working again, POKEY passes games self test Game works!

Game Board #53 02/05/2016

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

Game Board #54 01/31/2016
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/dianosis steps: RAM check 0x0000 - 0x03FF ok RAM check 0x0400 - 0x073f - BTS 0x80 @ 0x7A0 replaced M5 - OK - 23 minutes from start to finish

Game Board #55 01/31/2016

Problem: Game does not play Crystal is visibly missing Troubleshooting/dianosis steps: upon further inspection there are more missing chips C8 H8 J8 K8 B1 E2 replaced crystal and missing chips, no sync watchdog high, CPU looks OK WATCHDOG SHOULD have been watchdogging BUS test OK RAM test 0x0000 - 0x03ff BTS 0x04 @ 2c8 this is H2 pin 11 -> pin #5 @ E2, this might be a bad socket as the socket was replaced and damaged, verified connectivity between pins OK, removed 2114 @ H2 installed socket and replaced RAM, RAM test ok RAM test 0x0400 - 0x07EF - OK ROM test of D1, E1, H1, J1 failed 307, 308, 310, 211, 212. tested fine out of circuit 309 failed out of circuit, replaced let's test the address selection circuit chips reading OK though from the fluke on random addresses... odd 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) 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 game works! roms could use new sockets. sometimes game would start with mushrooms on right side of screen and soiund messed up, pushing on pokey fixed replaced pokey socket, seems to be OK trackball was non-responsive, noted someone hacked up the chips @ F10 and F11, removed and replaced, fixed burnt ground connector on edge connector Game works!

Game Board #56 02/05/2016

Problem: Blue screen with a bunch of zeros Troubleshooting/dianosis steps: 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. ram check 0x0000 - 0x03ff - OK ram check 0x0000 - 0x7EF BTS 0x00F @ 420 and OK till 0x460 that's M7, replaced - OK found what looks like a small piece of tin foil on some chips underneath the board, removed screen still blue , game not starting, sometimes there are tiles, sometimes not pulled eproms to test 307 - BFA2 - OK version 3 308 - BAD (should be 14eb) 309 - OK 600D - version 3 310 - OK A93C - version 3 211 - BAD 212 - OK replaced with single ROM board http://www.arcade-cabinets.com/board_hacks/CENTIPEDE-R, and replaced F7 game still not boot with normal CPU, verified CPU POKEY is bad, replaced replacing CPU socket colors are way off, screen totally blue r73 is missing F9 pin 5 is dead, should be moving, well sometrimes moving, replaced no change color rom at e8 not getting a write signal ever! write is input #3 on c8 feed by 74ls32 @ a4 pin #3 on a4 was stuck low, replaced game works!

Game Board #57 03/28/2016
Problem: Game boots but just static characters on the screen Troubleshooting/dianosis steps: removed pokey, no change Checked clock pin #37 on CPU, 1.5Mhz - OK Checked watchdog pin #40 on CPU - watchdogging Pulled CPU and put in another Game works!

Game Board #58 04/30/2016

Problem: Trackball is messed up LED start lights stay lit always Troubleshooting/dianosis steps: Trackball was all "wiggy" Replaced 14584 @ E/F11, no chnage replaced all 1uf caps in the trackball circuit, no change replaced 74LS191 @ C11, no change replaced 74LS74 @ D11, now trackball movement is stable but will never go down replaced 74LS157 @ DE/11, trackball is now fixed 74LS259 @M10 controls the LEDs, it is never getting it's !OUT signal on pin #14 traced !OUT back to pin #3 (!OUT) on 74LS32 is never going low, even though its inputs should be taking it low, replaced game works!

Game Board #59 8/23/2016

Problem: Static garbage on screen Troubleshooting/dianosis steps: getting a watchdog and a clock 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. RAM test 0x0000 - 0x03FF long, failed @ 0x40 with BTS 0x80 error, a few other addresses with BTS 80 that's F2 put in F7 into a ROM socket to do a ROM test to validate bus - OK put in new socket and 2114 ram, still getting the BTS 0x80 errors bit 8 is always low on address 40 doing a long ram test from 0 - 0x37 getting DCD error on bit A2 looks like bit 0x80 on data is messed up, not sure what's up here. 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 pulled 2114 @ H2, repladed, issue seems to have gone away. Fluke RAM long 0x0000 - 0x03FF - OK 2101 @ M5 is missing, replaced Fluke RAM long @ 400 - 7EF 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 A6 to 2101 is generated from P7 74LS257, inputs to P7 look good as far as clock cycles, pulled 72ls257, tested ok, 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 replaced bad socket used single rom hack and modifing one of the other ROM sockets to take the single ROM bad sound, replaced POKEY - OK high score save doesn't work swapped EAROM, - no change replaced 555 timer - OK put back original EAROM - OK Game works!

Game Board #60 9/16/2016
Problem: High score circuit doesn't work Troubleshooting/dianosis steps: Replaced ER2055 @ E5 with known good ER2055 - no change replaced 555 timer @ B11 - no change validated !write2 signal @ a4 #5 was good, valided !EA ADDR @ a4 #4 went low at the end of a game valided pin #6 @ a4 went low at the end of the game Found 74LS175 @ E4 bad, replaced Game works!

Game Board #61 9/20/2016

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/dianosis steps: pushed on PROM that handles Syncing (82S129 @ P4) when pushing on it sync got better or worse replaced socket, sync issue fixed Pushed on video ROMS at F7 and HJ7, lines went away replaced sockets on video ROMS, problem fixed Still having multiple sprites across the screen (4 shooters, 4 spiders etc), still having color issues, still having sprite object shape issues The repeated sprites and messed up sprite shapes are most likely the 74LS83 counters @ F6 and H6 inputs to h6 and F6 seem OK replaced E7 no change - put back original A5 and B5 tested OK C5 tested OK L8 tested OK pulled 74LS83 @ F6 - tested bad - replaced, seemed to fix the messed up sprites, but still multiples pulled 74LS83 @ H6 - tested bad - replaced, fixed the multiple sprite problem 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. game works!

Game Board #62 11/4/2016

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/dianosis steps: pulled pokey - no change checked clock - clock seems ok fluke bus test ok fluke RAM long 0x0000 - 0x03FF - RW err @ 0x0000 BTS 15 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 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. got to be a decoding error or an error with the data bus do looping read 0x0000 check pin #8 /CS on either 2114 RAM got good CS signal 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 looks like we are settings bits probably a buffer error let's try same @ 0x0400 w @ 0x0400 value 0x00 r @ 0x4000 = 0x11 w @ 0x0000 value 0xff r @ 0x4000 = FB both memories have the same issues common part in both circuits is E2, let's replace chip tested bad out of circuit however replaced, same BTS issue same test with video RAM still same result. taking out ROMs get a different RAM result, this tnme BTS 0x05 for 2114 range trying video rom range same result write tests of same values above are now showing write of 0x00 returns 0x01 and write of 0xFF returns 0xFB need to do some ROM test to isolate issue to specific part of address or data bus or decoding. next step is to examine the address selection circuitry verified writes to 0x00 do not affect 0x0400, not an address selection issue Started looking at the circuitry of the data signals that are messed up pin #4 (Data Bus #3 (DB2)) on E2 is tied to ground used capacitance meter to find short between DB2 and GND @ 74LS244 @ h5 74ls244 tesetd bad in circuit. ok now getting BTS error 0x15 when ROM is in getting BTS error 0x01 when rom is out, and getting low bit stuck high on all memory writes found short between DB0 and +5v used ESR meter found short @ 2114 @ H2 replaced with new socketed RAM - fixed BTS error now getting RW error @ 0x1f0 BTS 80 error trying RAM long @ 0x0400 - 0x7ef to isolate - RAM test OK removed 2114 RAM @ F2 and replaced - RAM long @ 0x0000 - 0x03FF now OK put ROMs back in an not getting BTS @ 14 @ 0000 - most have a address decoding error or a bad buffer ok when only D1 is, get BTS 0x04 when E1 added, let's switch D1 and E1 see what happens putting E1 into D1's slot get issues, E1 must be bad put back D1, add FH1 - OK put J1 in E1 - getting BTS 0x10 errors, must be bad replaced E1 and J1 all ROMs in now game now looks like it's booting but junk tiles can still see some of the test screen though put in new 2 video ROMS, now have a blank screen but test mode looks OK when pressed, actually ROM D1 reading bad replaced D1 now game works tested video ROM @ F7 211 out of circuit - OK tested video ROM @ HJ7 out of circuit - bad 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 replaced bad 74LS191 now game works except high score save does not 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! game works!