Teenage Mutant Ninja Turtles sound distortion

Eddie306

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I have a 4 player TMNT PCB that I currently installed into a Sunset Riders cabinet. TMNT plays fine, but the sound is distorted. While playing the game the music will play fine, but when sound effects come into play the sound along with the music gets distorted. If you defeat all of the enemies on screen, then the music kicks back in. Anyway, any ideas on what could be causing this issue? Thanks in advance for all of your help.
 
The sound works fine until I guess the game warms up. I was able to get to Scene 2 until it started getting really bad. Does anyone know if this is a bad chip or a cap going out?
 
I'm still not really familiar with arcade sound debug (or your cabinet) but, have you taken an ohm reading on the speaker and physically checked it out? Is the cone cracked or surround weathered? If it's a typical 8ohm speaker try hooking it up to a home stereo and see if it does the same thing or not. I'm not sure what type of audio output your board has but, does it run to an external audio amplifier pcb? If you do or don't just try hooking up a different 8ohm speaker and see if you get the same results.

You also might look to see if there's some sort of passive crossover on the speaker. If not, then all the lower frequencies could be playing through this speaker as well causing your distortion. Which seems consistent with this type of distortion -> game music (light, higher frequencies) and game sound fx (thumps, booms, lower frequencies). If this is the case a simple RC passive crossover will work just fine.

Or if you do have a pcb amplifier it could be experiencing problems which is a whole other ball of wax.

What size of speaker(s) is it? How many? I'll try looking the pdf up on the game cabinet but, this might be enough to get you started at least. Hope this helps.
 
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That era of Konami PCB's (Sunset Riders, X-Men, Lethal Enforcers, TMNT, etc) have been known to have sound issues with the on-board sound amp. Unfortunately, to the best of my knowledge, the amp is no longer available to buy, so you are most likely stuck with a board with no sound, or you can strip another PCB out for the sound amp to fix your Turtles. I could be wrong, though, perhaps these sound amps are available, and I'm unaware of it? Other than that, try the usual. Clean all the chip sockets, re-seat all the chips on the board, etc.
 
It does not run to an external audio amplifier pcb. It comes directly from the Jamma connector to the 8 ohm audio speaker(1). I might just get another TMNT board and see what happens. Thanks.
 
He's referring to the hybrid chip which amps the sound. Its permanently attached to the PCB in one of the corners (dont remember which one). Its a black chip with caps on it with a black coating on top. If your PCB has this (which it likely does), your caps are probably leaking and eating away at traces underneath the coating. It will start of with the sound cutting out and getting static and then youll eventually just lose sound alltogether.

I had a similar experience with an X-Men PCB as documented here:

http://forums.arcade-museum.com/showthread.php?t=91116

Might want to check this out, I got some good info from posting this.
 
TMNT does not use the custom chip listed above.

Correct. I have 2 TMNT boards with the same audio issues. You can
however bypass the on board amp and feed the two audio channels
to an external amp.

JD
 
Correct. I have 2 TMNT boards with the same audio issues. You can
however bypass the on board amp and feed the two audio channels
to an external amp.

JD

Holy necro thread bump!

However, on the subject of TMNT audio issues: There are some pesky LM324 and LM358 opamp ICs in the audio circuit that will cause this when they go bad.
 
pcjohn, tell me more....

I'd rather bypass the pcb amp until I can get my lm324s and lm358s installed.

Where do I pull the sound to send to external amp?
 
channelmanic: I believe I see two lm324 and two lm358. They are silk screened as upc324 and LA6358 on the pcb. Are those the correct ones to replace? I have the sockets and IC ready to roll.
 
Had a hell of a time removing the first 358. Installed socket and IC. Tested for the hell of it after installing the single 358 and it's a lot better. Only distorting here and there.

Have to get up at 5:30am est, so I'll finish tomorrow and test.

Still would like to know where to tap into the sound output to bypass pcb and and use external amp. Good to know and document.
 
Have you gentlemen replaced the ceramic resonator on the PCB?? It drives the audio and has been prone to failure. It solved my TMNT audio issue same as your describing. Cheap from digikey. Shipping going to cost more then the chip. Small square blue looks like this
 

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looks like I may be "upgrading" my soon to be acquired TMNT. Too bad X-men wasn't produced like these boards... grrr
 
Have you gentlemen replaced the ceramic resonator on the PCB?? It drives the audio and has been prone to failure. It solved my TMNT audio issue same as your describing. Cheap from digikey. Shipping going to cost more then the chip. Small square blue looks like this

Most of time it happens that the resonator is stripped away or the legs loose contact with its body during storing or handling.It happened me a couple of times.
 
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