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Thread: Tandy Sound Compatible PCB

  1. #21

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    PCBs are back - anyone wanting to test the rev.1 can order them now:

    https://www.lo-tech.co.uk/product/ta...9-adapter-pcb/

    Usual new product warning - this adapter hasn't been built yet so may or may not work!

  2. #22
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    Great, I just ordered one!
    I've dabbled with electronics back in the dark ages, when I could go to a local store to buy resistors, capacitors and all that stuff in low quantities... But those stores have all closed down. Any recommendations of where I could order such stuff online?
    I know the SN76489 probably won't be available at such a shop, so I probably need to get that second-hand from Ebay or such instead (or perhaps buy some broken donor-console from Sega or such, if that turns out to be cheaper).
    Last edited by Scali; November 19th, 2016 at 04:56 AM.

  3. #23

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    The full bill of materials with part codes for Mouser and Farnell will be published shortly

    Make sure to get the correct sound chip, it needs the AN suffix.

  4. #24
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    Quote Originally Posted by pearce_jj View Post
    Make sure to get the correct sound chip, it needs the AN suffix.
    Yes, the 'A' model means it has an 'AUX' input, right? Which you use to mix in the PC speaker?

  5. #25
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    Quote Originally Posted by Scali View Post
    Great, I just ordered one!
    I've dabbled with electronics back in the dark ages, when I could go to a local store to buy resistors, capacitors and all that stuff in low quantities... But those stores have all closed down. Any recommendations of where I could order such stuff online?
    I know the SN76489 probably won't be available at such a shop, so I probably need to get that second-hand from Ebay or such instead (or perhaps buy some broken donor-console from Sega or such, if that turns out to be cheaper).
    Unless that Sega console is an SG-1000 or 3000, you won't find a discrete chip inside one.

    Quote Originally Posted by Scali View Post
    Yes, the 'A' model means it has an 'AUX' input, right? Which you use to mix in the PC speaker?
    No, the chip with the mixer pin is the SN76496. The A suffix means that the waveform output is not inverted.
    My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

  6. #26
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    Quote Originally Posted by Great Hierophant View Post
    No, the chip with the mixer pin is the SN76496. The A suffix means that the waveform output is not inverted.
    Ah right... I've studied the PCB somewhat, and it seems the PC speaker and SN76489 are coupled directly to the amplifier with some resistors.
    I've checked the wiki... The 'N' is really important, since that is the 'narrow' DIP package. So the other version won't physically fit on the PCB.
    Not sure if the non-'A' would be so bad really. The inverted waveform would technically be wrong, but you'd still hear sound, and it'd be hard to tell whether it's inverted or not, except for some extreme cases I suppose.

    The SN76496 is also available in an 'N' package, so I guess in theory you could use it as well (same pinout, but pin 9 is the audio in, could be connected to gnd I guess).
    The wiki page is a bit confusing, since it says that the SN76496 is the same as the 'A' variation of the SN76489, but below there's a table that also mentions an 'SN76496A'. A quick Google image search only turned up 'SN76496N' though...

    Edit: The Google search also uncovered this ISA card with multiple SN76489AN chips... what the heck is this thing? http://pic.twitter.com/pRMYXWv6IS
    Last edited by Scali; November 19th, 2016 at 09:02 AM.

  7. #27

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    The variants have different input clock requirements. The non-A suffix parts have a divide-by-8 function on the clock input removed.

  8. #28
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    Quote Originally Posted by pearce_jj View Post
    The variants have different input clock requirements. The non-A suffix parts have a divide-by-8 function on the clock input removed.
    Ah right, great that such important information is not clearly mentioned on the wiki page. I'll just resort to the datasheet then.

  9. #29
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    Quote Originally Posted by Scali View Post
    Edit: The Google search also uncovered this ISA card with multiple SN76489AN chips... what the heck is this thing? http://pic.twitter.com/pRMYXWv6IS
    That card is 12 pins shy of an ISA connector

    It is a clone of the Apple II ALF Music Card MC1 : https://en.wikipedia.org/wiki/ALF_Pr...Music_Card_MC1
    My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

  10. #30
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    Quote Originally Posted by Great Hierophant View Post
    That card is 12 pins shy of an ISA connector

    It is a clone of the Apple II ALF Music Card MC1 : https://en.wikipedia.org/wiki/ALF_Pr...Music_Card_MC1
    Oh right, I'm not familiar with Apple II. Didn't know their expansion cards were so similar to ISA. So it's not some poorly known early PC soundcard then

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