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Thread: ZX Spectrum +2/+3 boards: a small guide

  1. #1
    Ya' Like it Retr0? VIP Zetr0's Avatar
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    Quote Originally Posted by rkauer View Post
    I know, mate. But the missing logic is just a pair of TTL chips and a ROM.
    My friend, most of +2A Spectrum's actually have the FDD part cut completely away =(

    The Spectrum +2A/B and +3 are part of the +5v/+12v /-12 switching power family (as opposed to the classic 9volt internally regulated family)

    here is a +2A/B motherboard


    I have two +2a's here (one of them is my friend Beaker71's) and they are like the above, also my friend Yorkie4's is the same.


    Here is a +3 motherboard


    As you can see the entire portion where the Zilog FDC and a smidge of supporting logic has been completely cut away.


    Now, some of the later +2A/B Spectrum motherboards were in fact complete +3 motherboards, however they had the Zilog FDC and some supporting logic not installed on the motherboard (probably to save costs) .

    Image missing in action

    The irony is I was reviewing an image of these boards not so long ago - I shall keep looking for an image.

    For the most part the +2A/B motherboards wont have the FDD option available to them, and those that do will require the hard to find Zilog FDC - although I seen replacement FDC's made from a WD1772/3 - apparently Atari ST's are a good source for these chips (*hehehe*)

    However the upside of the +2A/B is that it uses the same ROM as the +3, which means you can easily add an 8bit IDE interface by a small very cheap to make adapter (only a 74LS10, BC327, a 100K resistor, a 40 pin IDE header and a 56 way Edge connector) oh an the +3e ROM =)


    So to complete the ZX (9 Volt) family (and the post) -

    Heres the classic 48K/48K+ Motherboard


    Heres the 128k (Toast Rack) Motherboard



    Here is the 128K +2 (gray model)



    I hope that helps, the +2A/B Spectrum's are very exciting machines to be honest and I am sure that this will make its future owner very very happy.
    Last edited by Zetr0; 2nd August 2012 at 00:01. Reason: typo's and a bad grandma =)
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    The above post is so full of win that it deserves its own thread on the Oracle area.

    Well done, Zetr0!
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    Well I can do a little and complete the pics by providing some pics of a Issue 2 ZX 128K +2A witch as the full +3 pcb but of course with the +3 logic removed from the motherboard.
    This is in my possession and the RF as been removed due to really bad shape of it. The unit is a Spanish version +2A.

    Also have an English Issue 2 with socketed ram chips but pcb is cut as the one in the 1st post. All other +2A that I have is with the pcb cut and all English ones.
    Attached Thumbnails Attached Thumbnails IMG_5870.jpg   IMG_5871.jpg  

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    Ya' Like it Retr0? VIP Zetr0's Avatar
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    Thanks for posting that JLP, that's a great completion of the boards. For those that need full completion please have take a moment to review www.worldofspectrum.org there's an immense wealth of knowledge and camaraderie' there =)

    BTW, did that Tea2000 chip ever make it too you.... I sent it the same time I think as some 74F74's to a fellow EAB'er in itally... alas he never got his chips =(


    And to the staff member that split this from the sale thread: Cheers
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    Quote Originally Posted by Zetr0 View Post
    As you can see the entire portion where the WDC1773 FDD controller and a smidge of supporting logic has been completely cut away.

    Now, some of the later +2A/B Spectrum motherboards were in fact complete +3 motherboards, however they had the WDC FDD controller and some supporting logic not installed on the motherboard (probably to save costs
    That's interesting. So how does the +2A work with an external disk drive then? Did the 3" disk drives have all the necessary control logic inside the actual drive?
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    Talking Slightly random addition.

    My miniature UHF Video Transmitter (ASTEC UM1233) made from a spare (modified) Sinclair Spectrum 48K RF module: http://www.youtube.com/watch?v=Kjnz7mOPIRw

    Never got round to including the sound; sourced separately in that video.

    Just for fun.
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    Ya' Like it Retr0? VIP Zetr0's Avatar
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    @Andy

    Quote Originally Posted by AndyLandy View Post
    That's interesting. So how does the +2A work with an external disk drive then? Did the 3" disk drives have all the necessary control logic inside the actual drive?
    Alas my friend a +2A/B cannot use an FDD without replacement of the logic (if available on the motherboard) or by an adapter via the Z80 port.

    Its not that difficult to add a Floppy Disk Drive to any spectrum - from the humble rubber key 48 - upto the +2A/B's, in fact the only difficult part is sourcing some of the components these days.

    When I get caught up with some stuff I plan to make a Floppy Drive controller with a how-to

    Quote Originally Posted by skippy View Post
    My miniature UHF Video Transmitter (ASTEC UM1233) made from a spare (modified) Sinclair Spectrum 48K RF module: http://www.youtube.com/watch?v=Kjnz7mOPIRw

    Never got round to including the sound; sourced separately in that video.

    Just for fun.
    LOL, glad I dont have a TV license - that Super Grass Suck LOL!!!

    Awesomes stuff though m8y
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    Quote Originally Posted by Zetr0 View Post
    @Andy

    Quote Originally Posted by AndyLandy View Post
    That's interesting. So how does the +2A work with an external disk drive then? Did the 3" disk drives have all the necessary control logic inside the actual drive?
    Alas my friend a +2A/B cannot use an FDD without replacement of the logic (if available on the motherboard) or by an adapter via the Z80 port.
    So it would seem. I had a good ol' peruse of my +2A manual (which for some odd reason, I hung on to, despite getting rid of everything else), the Amstrad-Approved™ method was to buy an Amstrad SI-1 interface and an Amstrad FD-1 diskdrive. It's been a long time!
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    Wonder why we didn't move this thread to Amioracle and stick it!
    David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
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