Image Map Image Map
Page 25 of 25 FirstFirst ... 152122232425
Results 241 to 243 of 243

Thread: I wish to create a new DMA/RAM expansion card for the Tandy 1000 line.

  1. #241
    Join Date
    Feb 2017
    Location
    Chilliwack, BC, Canada
    Posts
    375

    Default

    Quote Originally Posted by Eudimorphodon View Post
    I was a little worried I was coming across as pestering.
    Not at all
    I just wish I had more time to tinker.

    Yes, the output of the first inverter gate drives the second. Though it did take a little bit getting used to seeing the power LED that has been steady green for 30+ years flash red, the last thing I want to do is drill a hole in the case. But like I said, I've been quite happy with how it turned out.

    As for the gutter, as long as the chips are mounted straight to the board (not socketed) you should be able to line them up with pin 1 on the PLUS header.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

  2. #242
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    1,262

    Default

    Quote Originally Posted by blackepyon View Post
    As for the gutter, as long as the chips are mounted straight to the board (not socketed) you should be able to line them up with pin 1 on the PLUS header.
    The modem board has few components that violate that; there's a metal isolation transformer that goes as far as the pin 2 row near the connector itself, and there's a big fat... filter? on the other side that's .4 inches past the top of the PLUS header. (The latter overhangs part of top the battery holder on my RAM board; if it got as far as the positive contact it would actually be a problem, but as is it *just* fits. It's that I think might have had a problem with the '245, at least if it sat high in the socket for some reason.) Of course, it's not like I'd be likely to ever plug that board in again if the serial card works...

    So I took a deep breath and submitted both boards to be run off just now, after going through them both one final time. The CF board is so simple I want to be confident about it and the serial board is at least *conceptually* fairly simple, but I'm not counting any chickens, or pterosaurs, before they hatch.

  3. #243
    Join Date
    Feb 2017
    Location
    Chilliwack, BC, Canada
    Posts
    375

    Default

    Quote Originally Posted by Eudimorphodon View Post
    The modem board has few components that violate that; there's a metal isolation transformer that goes as far as the pin 2 row near the connector itself, and there's a big fat... filter? on the other side that's .4 inches past the top of the PLUS header. (The latter overhangs part of top the battery holder on my RAM board; if it got as far as the positive contact it would actually be a problem, but as is it *just* fits. It's that I think might have had a problem with the '245, at least if it sat high in the socket for some reason.)
    I realized that they violated in horizontal alignment, what I was curious about was vertical clearance. The '245 on the Tandy DMA/RAM card is closer to the gutter than yours, in line with pin 2 on the header, about just behind where the phone jacks on the modem board sit (at least so it looks from the photos), but it's soldered directly to the board. With my current setup, the PLUS-CF card sits directly below the inverted ISA I/O card, so the components face each other. The lower board has everything socketed (for prototyping, so I wasn't frying the chips with all the re-wiring), and the ISA card has jumper pins, so there's only a couple millimetres vertical clearance.

    For the final product, I'd have everything just soldered straight to the board, other than RAM, ROM, and battery. Of course, if we were going for SMD, clearance would be a non-thought, but that severely limits who'd want to buy such a board as a kit to assemble themselves. For the battery, you might be able to shave off a couple millimetres by going with a surface mount battery clip, and these are very easy to solder on by hand.

    Also, because I want to put the '245 next to the data lines on the PLUS header, how many pins down the PLUS header does the transformer go?
    Last edited by blackepyon; Yesterday at 10:00 PM.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •