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Joytsick Interface damaged Spectrum

KorinelKorinel
edited January 2015 in Hardware
Hello All,

Sob.. I am a plonker, I did the cardinal sin, I was testing a bunch of joystick interfaces that I got off ebay and one didn't have the keyway and now I don't have a working Spectrum 48K+ (6A)!

I get a black screen, border and inner, but I checked the ULA and it's fine.

The voltages on the lower RAM are not correct, it appears I have lost -5v and +12v. Does this mean the lower DRAM is now toast?

My coil has some modification (done prior to me owning the board) to it so I'm not sure how to test it. Basically under the board there's a resistor linking the two outer pins of the coil. A second modification goes to R61 from the bottom inner pin of the coil. Does anyone know what this is?

Using a MM and testing TR 4 I'm getting 6 and 1193 on the legs (+ in middle) and 0 and 693 (- in middle).

For TR5 I'm getting 778 and 776 on the outer legs (- middle) and 1515 and open circuit (+ middle).

So I assume TR4 is toast but TR5 is okay?

Is there anything else I should check?

I should be put in stocks for a week and everyone throw rotten fruit and veg at me! I can't believe I did this!
Post edited by Korinel on

Comments

  • balfordbalford
    edited January 2015
    Don't worry, it happens the best of us, did I mention the time I killed a perfectly good ULA by attempting to test some 4116's I harvested from a broken board... :(

    Your 4116's may have survived - I'll pop in a new TR4, check resistances as per Zorn's video, power up and test voltages and then go from there. You may be lucky :)

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • SpiranthoSpirantho
    edited January 2015
    I always change tr4 and tr5 at the same time... saves stress later when they blow each other up! :)
  • KorinelKorinel
    edited January 2015
    Bah :( replaced TR4 and TR5 but it made no difference :(
  • balfordbalford
    edited January 2015
    If it's only -5v that's missing, check C46 and D19. Otherwise one of the 4116's is still shorting the supply rails, so you'll need to whip them out.

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • KorinelKorinel
    edited January 2015
    It's still both voltages 12v and -5 :(
  • DEATHDEATH
    edited January 2015
    Ok, take a step back - you've changed TR4 and TR5 and the voltages are still wrong?

    Personally, I'd remove ALL the lower RAM chips, make sure there are no solder splashes, then tackle the power supply. Get the power supply giving the correct voltages, then replace RAM chips with sockets, and replace RAM chips with one of Zorn's lower RAM boards and just pray you don't need an upper RAM board too.

    A word of warning - issue 6 boards are notorious for having traces that un-bond themselves from the PCB substrate as soon as you look at them. I'd personally leave it to one of the techs on here (Ian, Zorn etc).
    Oh bugger!<br>
  • KorinelKorinel
    edited January 2015
    DEATH wrote: »
    A word of warning - issue 6 boards are notorious for having traces that un-bond themselves from the PCB substrate as soon as you look at them.

    The Coil mod is throwing me somewhat, not sure what it is doing, any ideas?

    Yep, I learnt that recently :) http://www.worldofspectrum.org/forums/showpost.php?p=800492&postcount=33
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