PCB Repair Logs TMNT Teenage Mutant Ninja Turtles

TMNT - Teenage Mutant Ninja Turtles

TMNT

PCB Image	TMNT PCB
Pin Out	Reserved

Repairer: Arcade King
Forum Thread: TMNT PCB Repair

TMNT donated by Joe

Board problems:
Vertical Lines in character graphics.
vertical Lines in background.
When put into test most Mask Rom k27 and H4 come up as bad.

Found a dead Data line pin 28 Q15 socketed and replaced mask rom with a 27c400 4 meg eprom. Background is now perfect. Replaced the Mask Rom H4 with another 27c400 and fixed the Character Graphics. Only problem remaining with this board is missing TMNT theme song.

I've concluded the mask rom D5 contains the intro song and its dead. I've found 2 dead 74ls393s which are connected to its address lines. Replacing those chips bring back the intro but its repeating and not in full.

Changing the mask rom @ D5 fixed the intro song and the board is now 100%!

TMNT board 2 from Joey

When you turn this board on you get a white screen which will flash after a few seconds. What it is actually doing is running the ram, rom test.

I probed around a bit and found the two 2018 rams were not outputting anything through the data lines.

Piggy backing some other 2018 rams I could just make out the ram rom screen with rams F22,F23,G27 and G28 registering bad. Thinking the rams were bad I started by removing F23 and F22 put some sockets in and fired her up. Didnt really change much, the ram error is still there.

Turns out the rams were fine. The only reason I could see the test was I was using slower 35ms rams where the board requires 45ms. Comparing with a working board it would see the CE,OE and WE are not working as they should.

The WE traced back to a 74ls32 pin 6. This chip enables data output to the 27ls245s connected to the rams and the WE as well among other things. The chips appears to be fine but once again comparing it to a working board the inputs at pin 2 and 5 are not pulsing when they should to enable the rams. Traced it back to a 74ls138 @ H25. The outputs were doing jack. Replacing the chip fired up the board although there is massive graphics and PCM sound corruption which is bad mask roms, the intro music is working but like the board above its all messed up. I've ordered some more 27C400.

Got the 27c400s and the following mask roms were bad, K27, H27, K4, D5.

Graphics and Intro music are 100%. The voices in game are not working and only a loud screech comes out. Being lazy I naturally assumed it was the 1 meg mask rom. Replaced it with a the equivalent Eprom 27c1000 but no change. Note to self. check the address lines MORE carefully. Problem was a broken track under the D7759C synthesizer chip. Pin 35 on the synth chip to pin 3 of a 74ls273 @ B16 was broken. Repairing the track fixed the sound.

TMNT board 3 from Joey

Problem: No Sound
Fix: Put the right amp on next time Joe

TMNT from Tom

Problems: Board constantly resets.
Fix: Found 2 dead ICs a 74ls107 @ G16 and 74ls74 @ I20

Problems: Board now boots up with Bad F22 and F23
Fix: Tracked some dead address lines back to a 74ls157 @ D25

Problem: board now boots but to the warning screen but hangs and resets with random voice sounds.
Fix: The CPU was socketed and I noticed was a 68010P8, Replaced it with the propper 68000 game now runs but with graphics corruption.

Problem: Graphics corruption in the background and characters.
Fix: Doing a mask rom test roms @ K27 and K4 are bad. Replacing them fixes the board.

TMNT Virgils

Problem: Corrupted Background graphics.
Fix: Mask roms test reveals bad H27, replacing rom fixes problem.

Problem: no in game voices, EG: Fire, Attack, hang on April etc.
Fix: Dead D7759C synth chip.

Board Originally had a bad mask rom @ H27. I didnt have any replacement roms at

The time so I put the PCB to one side. 3 or 4 months later I turned it on again and it had rows of zeros all over the screen in vertical columns. You could see in the background bad ram error.

Problem: Zeros all over the screen, Boot up tests indicated bad rams G28 and G27.
Fix: Replaced both rams board comes up ok.

Problem: Vertical lines in graphics.
Fix: MAsk rom test has H27 as BAD. Put a socket in and replaced rom. Only 3 original mask roms left on this board.

Problem: In test some 4 player and dip switches stuck on.
Fix: Bad 74ls253 @ D28. All these 253's are F(Fujitsu) IC's and they will all eventually fail. VERY common problem.

Problem: After a few minutes some of the sound starts crackling and fading out.
Fix: Faulty LM324 @ G 12. another common fault.

PCB now 100% until next time I decide to test it in a few months time.

2nd of my boards

When I plugged it in last I couldn't get into the dip switch settings now its developed more faults.

Problem: Displays ram F22 as BAD
Fix: Faulty 74ls245 @ C24

Problem: Dip switch set 3 not working.
Fix: Faulty 74ls244 @ D27

Game runs ok but after awhile developed more problems

Problem: Colour "flaky" particularly noticeable in the Purple in Donitellos square in the game into.
Fix: Faulty 74ls273 @ E23

Game ran ok for awhile again then developed more colour problems.

Problem: I noticed below the manhole in the intro it was casting a purple shadow and the turtles when they came out of it were mostly red! Resetting the board I now get a ram error F23 BAD.
Fix: the other 74ls245 @ D24 next to the one above @ C24 was faulty. All F(fujitsu) chips AS USUAL I'm really sick of turtles PCBs

Spoke too soon.

Problems: All character graphics "washed away" and are now just white. Background is fine.
Fix: Bad 74ls174 @ F25 and yep another F chip

Board 7

Repairer: Womble
Forum Thread: TMNT PCB Repair

Picked up a faulty TMNT on ebay a month or so back...



...the seller had bought it as a faulty board but had never got round to looking at it.

The board was totally untouched, beyond the fact the EPROMs had been swapped to change the game version. There wasnt a non-original solder joint on the board, but it was stone dead. My work bench had been offline for a while so I had tested it in my JAMMA cabinet, and it was very dead, not even a pop from the speaker on power up just a blank screen.

Once I got it on the bench I fired it up again and got the same result. Measuring the voltages at the board showed I had 0v on the 12V line and 0.2v on the 5V line.

The edge connector was clean enough so the only likely reason for this was that something on the board was shorting out the PSU. My old arcade PSU which crapped out on me a while back used to make a ticking noise when it was shorted by a bad board, this one it seems doesnt give any signs at all.

I gave the board a once over eyeball check looking for twisted caps or bent pins making contact and found nothing so it was time to divide and conquer.

TMNT only uses +5v and+ 12v and a short on either one could shut the entire PSU down. So I unplugged the 12V feed from the PSU and powered it back up, the board leapt into life!



So only the 12V rail was shorted, the 12v doesnt go to many place on this board and the most likely candidate for the fault was the 1000uf 16v decoupling cap at C20 that sits between the 12v and ground.



It's tall, thin and sticks up well above the other components so it is often knocked off, or damaged. This one looked fine physically and the legs were not loose inside, but the resistance measurements between the 12V and ground JAMMA pins went crazy when it was touched. Surprisingly its ESR was fine, however an ESR meter doesn't actually measure resistance to come to up with the reading, it measures a harmonic ringing effect which it then bases a calculation on to get the ESR value; in this case the cap was totally hosed.

So it came off the board...



...and a replacement salvaged this morning from a scrapped chassis was ESR tested and installed.



The game now runs fine with sound, amazingly (for a PCB loaded with Fujitsu TTLs and old mask ROMS) there were no other faults at all. I ran the in-depth RAM/ROM check, it passed and the game runs perfectly.



Result - took me ten times longer to write this up and upload the photos than it did to fix it

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