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TMNT Intro Music
Question from Kevin: Hello, this is Kevin and I recently purchased a Teenage Mutant Ninja Turtles arcade cabinet through eBay. The arcade works great! Graphics, sound effects and gameplay music are excellent. My only issue is with the lack of intro music. You hear sort of a buzzing sound in place of the music. I checked all dip switch settings and made sure SW2 8 was turned to ON for attract music. In fact, I verified the switches per the manual to make sure. This didn’t fix the issue. My guess is that a LS393 chip(s) have gone bad but I’m not sure where to begin. I have some soldering experience replacing sega game gear caps but have never tackled these through-board solders. Am I headed in the right direction with respect to troubleshooting? I’m not even sure where to find replacements for any parts that would fix the intro music. Any help you can provide is greatly appreciated! Thank you for your time! Sincerely, Kevin
1 answer
Response from Jonathan: Kevin,
Yes, this definitely sounds like some sort of issue with the board and replacing the LS393 chips is a great place to start. The process to replacing these is not much different that the Sega Game Gear caps you are familiar with. You just need to desolder the old chips, removed them and solder in the new chips. We like to use NTE for our replacement chips as they have a great part cross-reference search. According to their search. the NTE74LS393 should be a suitable replacement for the MB74LS393 chips that are probably installed on your board right now. You can order these from any of their distributors but we like Newark the best as we’ve had a lot of experience with them. Here’s a link to their page for this part: http://www.newark.com/nte-electronics/nte74ls393/logic-ic/dp/31C5728?ost=LS393&categoryId=800000004727.
Now, keep in mind that the problem could also be in the single mask ROM at D4 as that is where the theme tune sample is held. In this case, you will probably need to order a replacement ROM from Hobby Roms or another ROM burner (unless you have access to a ROM burner locally). The replacement process will be similar to the LS393s just with more pins.
Something I want to make clear is that this is very much a “shotgun” approach to trying to fix this issue. Basically we’re replacing all the chips that control this function in hopes that it will solve the issue. Your best bet to making sure you get it working is to get the proper tools (such as an oscilloscope) and make sure all of the chips/connections are functioning properly. You can also send the board to one of the people we have listed on our resources page under the Board (PCB) Repair & Component Sales heading for a list of people who specialize in board repair should you continue to have issues.
Hope that helps. Thank you for your question and good luck with your repair.
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