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Thread: Sinclair QL

  1. #1
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    Default Sinclair QL

    I picked up an NTSC Sinclair QL off ebay for $40. It needs a new keyboard membrane, which seems to be readily available. However it is also missing its power supply. I'm wondering how hard that would be to find or recreate, given it was probably a North American 110V power supply and the North American machines, to my knowledge, are rarer than the UK versions?

  2. #2
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    Default

    What are the voltage requirements?

  3. #3
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    Default

    It looks real weird...
    ...15.6v ac + 9v dc

    http://www.dilwyn.me.uk/docs/hardware/qlpsu.png
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  4. #4
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    Default

    It's even more weird when you look at the schematic (but what would we expect from Sinclair?)...

    There is a 3 pin power connctor that seems to be wired as follows:

    1 pin for 0V.
    1 pin for +9V dc. This feeds 9V into the circuitry plus feed the +5V regulator. Interestingly, this line appears to be also used as one side of the 15.6 V ac supply.
    1 pin for 15.6 V ac. This is half-wave rectified and feeds the +12V and -12V regulators.

    I would suggest studying the schematics and working out exactly which pins on the power connector do what BEFORE letting the black smoke out of the box!

    EDIT: I was thinking about this over lunchtime. The common reference for the +/- 12V regulators being connected to the +9 V dc rail is not logical! It 'should' be the 0V that is the common rail - otherwise the +/- 12V rails are not referenced to 0V but to +9V! Some probing with a multimeter called for I think... Perhaps this is the 'deliberate mistake' in the schematics...

    This is the schematic I was using http://www.sinclairql.net/srv/QLSchematicIssue5.gif.

    Also, the technical manual (http://www.dilwyn.me.uk/docs/ebooks/...20Research.pdf) in section 2.2.3 inadvertantly refers to the +9.0 V as a.c. instead of d.c.

    Dave
    Last edited by daver2; May 2nd, 2018 at 04:03 AM.

  5. #5

    Default

    You could have a look on the UK QL forum. Specifically this thread.

  6. #6

    Default

    Here the search I did some stuff you might find interesting.

    https://www.google.com/search?q=Maki...nt=firefox-b-1
    Never Bin or sell your old computer's you will regret it!!
    Vic 20 x3,C64 x2,128D,C128 flat deck,A1000 x2,A500 x3,A2000,A600,A1200,Apple ][e,2x Apple][ GS rom 01,03,Apple ][c x4 with only 1 PSU,2x Laser 128EX EX2,Atari 600XL,2x 800XL,130XE w/320 mod With a MyIDE plus,Atari 1040stf w/2.5meg..

  7. #7
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    Default

    Thanks guys. That ATX psu solution looks suitably nightmarish!!

    Maybe I'll get lucky and hit upon one on ebay. I pulled off finding boards for my Poly 88, so theres hope.

  8. #8

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    That sounds similar to my Timex 2068. I ended up using an old laptop power supply and it worked fine.

  9. #9
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    Default

    Quote Originally Posted by tempest View Post
    That sounds similar to my Timex 2068. I ended up using an old laptop power supply and it worked fine.
    Isn't the 2068 single voltage psu? the QL needs some AC as well...
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

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