zx spectrum broken, help with repair - Sinclair

This is a discussion on zx spectrum broken, help with repair - Sinclair ; Hello all, recently aqcuired a zx spectrum 48k, with which i was very happy.. for 15 minutes that is, until it 'broke down'. screen display is completely garbled; sometimes i only get white noise, but most of the times a ...

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Thread: zx spectrum broken, help with repair

  1. zx spectrum broken, help with repair

    Hello all,

    recently aqcuired a zx spectrum 48k, with which i was very happy.. for 15
    minutes that is, until it 'broke down'.

    screen display is completely garbled; sometimes i only get white noise,
    but most of the times a mixed up display, colors, charblocks and diagonal
    lines all over the screen.. When I press the custom reset button i
    clearly see the borders and a few blinking charblocks. Hard to explain
    really. I first suspected the rf-modulator, but this all sounds like a
    bit more is going on.

    I did try another PSU, same results. Any suggestions to where I have to
    start repairing the machine would be most welcome!

    thanks in advance!

  2. Re: zx spectrum broken, help with repair

    Does it ever work? I assume from having a reset that its a + not a rubber
    key version?

    There used to be a lot of trouble with damage to the pcb where the psu
    connector went in. Also the psu leads themselves were pretty naff if you
    tripped over them.

    This all assumes it will boot sometimes, if never then it sounds like
    problems elsewhere.

    Overheating ram chips can cause time related crashes like this, but if its
    died permanently, it could be almost anything. Might be worth checking if
    anything inside is in a socket and has worked loose.

    Brian

    --
    Brian Gaff....Note, this account does not accept Bcc: email.
    graphics are great, but the blind can't hear them
    Email: briang1@blueyonder.co.uk
    __________________________________________________ __________________________________________________ __________


    "fier" wrote in message
    news:482cd18a$0$426$e4fe514c@dreader13.news.xs4all .nl...
    > Hello all,
    >
    > recently aqcuired a zx spectrum 48k, with which i was very happy.. for 15
    > minutes that is, until it 'broke down'.
    >
    > screen display is completely garbled; sometimes i only get white noise,
    > but most of the times a mixed up display, colors, charblocks and diagonal
    > lines all over the screen.. When I press the custom reset button i
    > clearly see the borders and a few blinking charblocks. Hard to explain
    > really. I first suspected the rf-modulator, but this all sounds like a
    > bit more is going on.
    >
    > I did try another PSU, same results. Any suggestions to where I have to
    > start repairing the machine would be most welcome!
    >
    > thanks in advance!




  3. Re: zx spectrum broken, help with repair

    Brian Gaff wrote:
    > Does it ever work? I assume from having a reset that its a + not a rubber
    > key version?
    >
    > There used to be a lot of trouble with damage to the pcb where the psu
    > connector went in. Also the psu leads themselves were pretty naff if you
    > tripped over them.
    >
    > This all assumes it will boot sometimes, if never then it sounds like
    > problems elsewhere.
    >
    > Overheating ram chips can cause time related crashes like this, but if its
    > died permanently, it could be almost anything. Might be worth checking if
    > anything inside is in a socket and has worked loose.


    Aye, and I already suggested feeling all the chips to see if one's running
    hotter than the rest... A fairly simple test for chip failure. And as it was
    time related it does imply overheating might've been the initial cause...
    --
    | spike1@freenet.co,uk | "Are you pondering what I'm pondering Pinky?" |
    | Andrew Halliwell BSc | |
    | in | "I think so brain, but this time, you control |
    | Computer Science | the Encounter suit, and I'll do the voice..." |

  4. Re: zx spectrum broken, help with repair


    "Andrew Halliwell" napísal

    > Aye, and I already suggested feeling all the chips to see if one's running
    > hotter than the rest... A fairly simple test for chip failure. And as it
    > was
    > time related it does imply overheating might've been the initial cause...


    Even simplier : Have to check all pins of chips if there is not short
    circuit in a chip, especially ram chips are very sensitive for breakthrough.

    B


  5. Re: zx spectrum broken, help with repair

    On Fri, 16 May 2008 22:12:30 +0200, Bohus Král wrote:

    > "Andrew Halliwell" napĂ*sal
    >
    >> Aye, and I already suggested feeling all the chips to see if one's
    >> running hotter than the rest... A fairly simple test for chip failure.
    >> And as it was
    >> time related it does imply overheating might've been the initial
    >> cause...

    >
    > Even simplier : Have to check all pins of chips if there is not short
    > circuit in a chip, especially ram chips are very sensitive for
    > breakthrough.
    >
    > B



    thanks for all the tips guys.

    I just replaced the ULA from a broken +, (with some remote help from
    andrew), and the machine is working again
    very happy ofcourse.. I am just wondering if a similar breakdown in teh
    future can be prevented in some way. Can it be that the coil or the
    heatsink are defective? If not, I can have a relaxed sleep knowing that
    the machine is saved for a while

    thanks again!

  6. Re: zx spectrum broken, help with repair

    I don't think anyone can say if it will occur again. The chips are now
    getting quite old and the heat cycling will no doubt make more of them fail.
    Knowing Sinclair, I doubt if much life testing was done on the ULA.
    Ferranti just made them, presumably churned them out to a price.

    Brian

    --
    Brian Gaff....Note, this account does not accept Bcc: email.
    graphics are great, but the blind can't hear them
    Email: briang1@blueyonder.co.uk
    __________________________________________________ __________________________________________________ __________


    "fier" wrote in message
    news:482e12d1$0$3612$e4fe514c@dreader19.news.xs4al l.nl...
    > On Fri, 16 May 2008 22:12:30 +0200, Bohus Král wrote:
    >
    >> "Andrew Halliwell" napísal
    >>
    >>> Aye, and I already suggested feeling all the chips to see if one's
    >>> running hotter than the rest... A fairly simple test for chip failure.
    >>> And as it was
    >>> time related it does imply overheating might've been the initial
    >>> cause...

    >>
    >> Even simplier : Have to check all pins of chips if there is not short
    >> circuit in a chip, especially ram chips are very sensitive for
    >> breakthrough.
    >>
    >> B

    >
    >
    > thanks for all the tips guys.
    >
    > I just replaced the ULA from a broken +, (with some remote help from
    > andrew), and the machine is working again
    > very happy ofcourse.. I am just wondering if a similar breakdown in teh
    > future can be prevented in some way. Can it be that the coil or the
    > heatsink are defective? If not, I can have a relaxed sleep knowing that
    > the machine is saved for a while
    >
    > thanks again!




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