(Topic ID: 172192)

7408 ic substitute?

By PanaPinResto

7 years ago



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    #1 7 years ago

    I have a bad 7408 causing my ripper coil to lock on(DE lah). I don't have a 7408 but I do have a 7402,7404 and a tc4050. Will any of these work?

    #2 7 years ago

    None of those are even close. A 7408 is a quad AND gate. The 7402 is a NOR gate, the 7404 is a hex inverter, and the 4050 is a hex buffer. You'll have to order the correct part.

    #3 7 years ago

    That's what I figured. Thanks for the quick answer.

    #4 7 years ago

    When using a TTL gate to turn on a transistor (like WMS solenoid circuits), you have to use one that can handle some current.

    74F08 is what I would use as a still easy to find replacement.

    When Replacing 74LS parts you can use 74HCT.

    Only use 74HC when you are replacing another 74HC

    #5 7 years ago

    Now I'm confused. The post above says they are not even close. I think I have a bad ic at b12 on a data east rev3 board. Manual shows 7402, my board has 74f08. Will these work?

    image (resized).jpgimage (resized).jpg

    #6 7 years ago
    Quoted from PanaPinResto:

    Now I'm confused. The post above says they are not even close. I think I have a bad ic at b12 on a data east rev3 board. Manual shows 7402, my board has 74f08. Will these work?

    A 7402 and 7408 are certainly NOT interchangable. The input and output pins aren't even the same. Has the board EVER worked? If not, I would suspect that someone before you replaced it (and maybe both of them) with the wrong part. I tried looking at pics of a Data East board on Pinwiki, but the resolution is not high enough to read the part number off those chips. You should definitely verify before doing board work.

    #7 7 years ago

    Both the schematic and assembly drawing say those chips should be 7402. I'd still like to see 7402 on a board, but I think your board has the wrong parts on it.

    1-Fullscreen capture 10282016 24823 PM (resized).jpg1-Fullscreen capture 10282016 24823 PM (resized).jpg

    #8 7 years ago

    Both of those ICs in the pics look to have been replaced, based upon the appearance of the solder connections.

    #9 7 years ago
    Quoted from herg:

    'd still like to see 7402 on a board

    bttf here with 7402

    bttf 7402.jpgbttf 7402.jpg

    #10 7 years ago

    It fixed. I replaced both of those 7408's with............7402's. The coils no longer lock on. Clays guides says "7402/7408" for that spot. Not sure what the story is the the machine works great now. To answer the question above, no. It's never worked since I bought it.

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