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Thread: Picked up a NorthStar disk drive for my Sol-20

  1. #41

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    Also, one interesting thing about the cassette interface, using some types of tape recorders with the Sol, will result in destruction of the DIL relays (on the Sol's mobo) that switch the cassette transport motors on & off. To ameliorate this issue, PT put some 6.8R resistors in series with the relay contacts, but not all Sol's have these resistors fitted.

    I wrote an article about the cassette tape interface and the last section of it explains what can happen with these tiny relays. In my case I ended up modifying the tape decks to solve the problem that way.

    The cassette tape interface is quite interesting I think and in the Sol-20 version of it, they built a very good AGC system, with a Fet which significantly improves the performance recovering data from tape, the article is here:

    http://worldphaco.com/uploads/The_SOL-20_tape.pdf

    I have attached a photo of the cassette decks I used, Panasonic RQ-2765, these were NOS , I found them on ebay. They are well made, and I have the service manual, belts are still available too.

    All of these small decks have motors with a mechanical govenor (contacts) inside the motor, because of this there are accelerations and decelerations of the rotational speed which you can hear if you listen to a recorded tone, but these are not normally enough to upset the recording and recovery of data because of the way the tape interface works. More expensive cassette players with electronic motor servo controls do not have this issue
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    Last edited by Hugo Holden; September 19th, 2020 at 01:28 PM.

  2. #42

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    Hugo, Thanks for detailed paper on the cassette interface. If I fail to get my disk drive working, I may need to bring out my cassette recorder again. I had previously ordered a 9-pin female to 25-pin male cable, and, if I remember correctly, I used a 25-pin null modem adapter 10 years ago, so I am going to get a 25-pin null modem adapter. Hopefully, if I read the procedures correctly and remember how to use the Hyperterminal application, I will get the interface to work.

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