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Is my ZX81 RAM Pack OK?

dreamscapedreamscape
edited August 2014 in Hardware
Hi guys

I've just taken my 16k RAM pack apart to give it a clean inside and out and i noticed these strange burn type marks!?

IMG_20140826_181011.jpg

IMG_20140826_181137.jpg

You can see it mainly on the PCB where the chips etc connect to the PCB... is this burn marks!? Is my RAM pack damaged I haven't even tested this yet as I'm waiting for a RF cable...

Also is it me or are those capacitors bulging?

I just thought i'd check before connecting it to my ZX81...
Post edited by dreamscape on

Comments

  • balfordbalford
    edited August 2014
    Nope, that's dried in flux residue :) Perfectly common on these. Caps do look a bit past their best though, I'd renew before connecting.

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • dreamscapedreamscape
    edited August 2014
    Ok that's good news! Could you tell me what caps i need to buy for replacement please?
  • balfordbalford
    edited August 2014
    Unfortunately my collection's out of reach right now, however from memory there's a 100uf cap, a couple of 22uf ones, and two 1uf.

    You can check what's in front of you to be sure, same rules apply as on your other thread :)

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • DEATHDEATH
    edited August 2014
    That's just dried on flux residue left over from the manufacturing process. Just get an artist brush and some kitchen towel and put on a few drops of solvent over the residue, let it sit a while and then just dab it off gently with the kitchen towel. Suitable solvents are:

    IPA (iso alcohol) AKA tape head cleaner
    Acetone (AKA nail polish remover)
    MEK (Methylene Chloride) AKA polyweld, Nitromores paint stripper
    Parrafin (AKA kerosene, jet fuel, white spirit)
    Cellulose paint thinners
    Naptha should work too, sold as Zippo lighter fuel.

    Do I need to tell you not to smoke whilst playing with lighter fuel? Oh, and do I need to tell you not to play around with Meth Chloride? It's been linked with cancer apparently, although you can still buy it in the UK as a modeller's polystyrene cement.

    This is a great example of something I was trying to point out in a previous post. Again, meant with the greatest of respect to the original poster.... Those caps are well over 30 years old, you KNOW you should change them, even if they look (and work) just fine.

    Lloyd.
    Oh bugger!<br>
  • dreamscapedreamscape
    edited August 2014
    Thanks for the feedback guys I actually have some iso here so iv made a little start...

    IMG_20140827_040004.jpg

    I need to get a better brush will do that tomorrow as at the moment its hard getting into the tight areas but i've made it look abit better already.

    Before:

    IMG_20140827_034814.jpg

    After:

    IMG_20140827_040023.jpg
  • dreamscapedreamscape
    edited August 2014
    All cleaned

    Before:

    IMG_20140827_034814.jpg

    After:

    IMG_20140827_100845.jpg
  • 1024MAK1024MAK
    edited August 2014
    I waffled on about resistance testing 4116 DRAM chips in this thread :-D

    It may be helpful.

    Mark
    Sinclair FAQ Wiki
    Repair Guides. Spanish Hardware site.
    WoS - can't download? Info here...
    former Meulie Spectrum Archive but no longer available :-(
    Spectranet: the TNFS directory thread

    ! Standby alert !
    “There are four lights!”
    Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb!
    Looking forward to summer in Somerset later in the year :)
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