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Thread: Looking for Tarbell Cassette Interface Schematic

  1. #1

    Default Looking for Tarbell Cassette Interface Schematic

    Does anyone have a good copy of the schematic for the Tarbell cassette interface? I'm trying to recapture it in KiCad so I can make a PCB for a quasi-replica. I have found a couple PDF copies of the manual online, but they are scanned at fairly low resolution making it hard to make out some parts of the schematic.

    Thanks!

  2. #2
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    Isn't it in the manual? Pages 19 and 20. It doesn't include the power supply part (regulators), but otherwise is pretty complete.

  3. #3

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    Sure, I've been working from the manual so far, but some parts aren't very readable. It will probably be good enough to get the job done if nothing else exists. Thanks.

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    Hi All;

    Ab0tj, there's one in the S-100 handbook, along with a host of other schematics..

    THANK YOU Marty

  5. #5
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    Have you had a look through old issues of Kilobaud magazine and BYTE on archive.org?
    Searching 'tarbell' in a few 1977 issues I spotted
    Meet the Tarbell/KC Interface Kilobaud April 1977 p44
    Circuit Kilobaud February 1977 p128
    Cassette I/O Format Kilobaud August 1977 p18
    Profile of Don Tarbell Kilobaud May 1977 p139
    etc.
    ...lots more there, for the digging. They are a goldmine.
    Last edited by 1944GPW; August 9th, 2017 at 06:35 PM.

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    Quote Originally Posted by 1944GPW View Post

    Circuit Kilobaud February 1977 p128
    it is the circuit for the "Kill A Baud" PE 2400
    fun to re-read that article about the problems with all the formats though

  7. #7
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    Quote Originally Posted by Al Kossow View Post
    it is the circuit for the "Kill A Baud" PE 2400
    fun to re-read that article about the problems with all the formats though
    Fair enough, but can you explain this bit: "This article and a following one will tell you how to build your own PE 2400 interface. While basically intended for NRZ recorders, phase encoding can be used on audio recorders if the baud rate is kept high enough. A hobbyist cassette board using it is marketed as the Tarbell interface. Several other interface kits also can use it."

  8. #8
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    Quote Originally Posted by 1944GPW View Post
    Fair enough, but can you explain this bit: "This article and a following one will tell you how to build your own PE 2400 interface. While basically intended for NRZ recorders, phase encoding can be used on audio recorders if the baud rate is kept high enough. A hobbyist cassette board using it is marketed as the Tarbell interface. Several other interface kits also can use it."
    Kilobaud was trying to make their own standard which didn't have the problems they perceived the others to have, which is what they describe in the articles.
    Tarbell apparently used synchronous rather than asynchronous transmission, which required the use of the Intel 8251 serial chip, PE 2400 also used phase encoding but with asynchronous character encoding, 1 stop bit and even parity.
    They also didn't like checksums.

  9. #9
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    Quote Originally Posted by ab0tj View Post
    Does anyone have a good copy of the schematic for the Tarbell cassette interface?
    I found my manual this morning. PM me your email adr and i'll send the two schematic pages to you.
    I'll upload the whole manual to bitsavers later this week

  10. #10

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    Thanks all for the recommendations, guys. I ordered a used copy of the S100 Bus Handbook (should have one anyway), now I will be reading through lots of issues of Kilobaud magazine, and Al probably has a better scanner than whoever scanned the other manual found online - That one has been good enough to get started but has also led to a lot of questions like "Is that an AND or a NAND gate?" "Is there a junction there?" "Is that blob a 5 or a 6?" etc etc.

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