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#10 Williams F-14 Tomcat No Speech

Discussion in 'The Menace Files' started by Menace, Nov 24, 2014.

  1. Menace

    Menace Well-Known Member
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    Alright, so this one was interesting...

    IMG_20141118_162642 (Large).jpg

    This game came to me from a friend of a PB Rev member, and I had actually worked on this game in the past. I had to repair a small fire that broke out in the high voltage section a few years ago after being over fused by mistake. I will say it was an honest mistake as the power supply in this particular game is actually from a Data East game (one of Stern / DE's notorious PCB rip-offs of BLY/WMS designs) and the fuse labels in the game do not match the DE PCB designations. When an 8 Amp fuse is installed in the HV section when it should be a 1/4 Amp and things go wrong... well I'm sure you don't need me to paint the picture. Let's just say the event is now known in certain circles as the infamous F-14 fire of 2012. :cool:

    The issue with the game now was apparently intermittent sound and/or speech. The owner just happened to be moving to a new house, and being a sound board issue I knew I was going to have to bust out my scope for this repair, so we agreed for him to bring the game to my house so I could work on it in my shop.

    IMG_20141118_152204 (Large).jpg

    Powered the game up and noticed the PinLED displays were a bit wonkey and had some unwanted artifacts on the displays. Turns out the ribbon cable for the display has tarnished pins, and I confirmed this by powering the game off and reseating each end of the display ribbon cable a few times. Power the game up and all was good, and I've informed the owner that he should purchase a new ribbon cable on one of his next parts orders should the issue return. After running it through all the sound and speech tests, I confirmed all the sounds seemed to be present but no speech... but wait! It wasn't that there was NO speech, but very very VERY quiet speech. With the volume turned all the way up, you could just barely make out the speech calls!

    Now I cannot stress enough to anyone wanting to do their own troubleshooting how important it is to have all the proper documentation on hand. The game didn't come with a manual, but it is available on-line. Unfortunately for me, I spent over an hour scouring the internet for the correct schematics for this game. Why? Because the manual for this game comes with the incorrect schematics for the additional sound / speech PCB that actually came with the game! :picard: Ultimately I ended up having to download a copy of a Whirlwind manual as it had the correct schematics I required.

    Once I had all the correct documentation I could begin to formulate a plan. Sys11 sound can be tricky to troubleshoot because there were a few different incarnations released from the factory. This particular game is a Sys11A which means it has the upper left hand corner of the MPU populated with all of the sound / speech circuitry. Some of the games sound and speech is actually generated on the MPU and then sent out and mixed into the additional sound / speech board before being amplified and passed on to the speakers in the game. This was done because the MPU sound section is unable to handle large enough sound / speech rom's for this game.

    Where the game is actually generating all of the correct sound and speech, and the game didn't have any issues with playing the game sounds that pretty much eliminated the amp and logic sections and led me to focus on the pre-amp section. The trouble is which pre-amp section, as this game has one on the MPU and one on the sound/speech board and I needed to isolate which one was responsible for generating the speech calls. There is an audio line-out and data ribbon cable from the MPU to the sound / speech board, and by disconnecting the line-out and running the sound tests again confirmed the sound / speech PCB was generating all of the sound & music for the game which left the MPU to generate all of the speech. Using the schematics I came up with some points to probe on both the MPU and the sound / speech board (for reference as I knew it was working correctly) and I quickly determined that one of the 3 op-amps on the MPU was bad.

    Here is a picture of the op-amps I was probing with my scope. Each of these IC's is actually a dual op-amp and the top one was half bad. (the second op-amp in the IC was fine but not being used by the game)

    IMG_20141118_162552 (Large).jpg

    Based on some of the information I've read, failing op-amps is not a common issue but it's also not uncommon. Replaced the failed op-amp with a new one, and General Yagov lives to speak another day!

    D
     
    #1
    Last edited: Mar 18, 2015
  2. mwong168

    mwong168 Administrator
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    Thanks for sharing the repair write up and I hope this is sign of more Menace files postings to come now that your workshop is pretty much done!
     
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  3. Fifty

    Fifty Active Member

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    Great write-up menace! Thanks very much for posting this!
     
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  4. tkaye

    tkaye Active Member

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    Thanks as always Doug!
    Great work.
     
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  5. brewmanager

    brewmanager Active Member

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    Thanks Doug! You rock - and thanks for labelling it an honest mistake.
     
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