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<1234567…34>
  • Difficult to find upper RAM fault.I've recently repaired an issue 3B 48K Spectrum that had a tricky to diagnose upper RAM fault, so I thought I'd post a report of what I found here. …

    ... issue 3B 48K Spectrum that had a tricky to diagnose upper RAM fault ... was suspiciously short for a 48K Spectrum. Using PEEK to examine ... or larger areas of upper RAM and no problem was ever found.
    problem at the start of upper RAM, but I ...
    Zorn Zorn April 2012 Hardware
  • Issue 2 Upper Ram, Loading & ResettingI have a 48k Issue 2 Speccy and for the life of me can't track down what the problem is with it. I initially thought that some of the uppe ram ic's w…

    I have a 48k Issue 2 Speccy and ... t track down what the problem is with it. I initially ... 65535 returned as expected for 48K. Turned the Spectrum off ... then replaced all the upper ram with known good ram from another Issue ... I try and load a 48K game, it loads all ...
    retrogamemart retrogamemart December 2014 Hardware
  • Alternative chips for upper RAM blockDoes anybody know of a way to use 4464 chips instead of 4164 for the upper RAM block in a 48K machine? If not 4464 then something a little more avai…

    Does anybody know of a way to use 4464 chips instead of 4164 for the upper RAM block in a 48K machine? If not 4464 then something a little more available than the 4164. Winston? Piters??

    TIA
    DEATH DEATH August 2007 Hardware
  • Upper RAM replacement module issues with the DivideI got my new upper ram replacement module from Zorn yesterday and seem to be having some issues. When the machine is without the Divide it boots up …

    ... also seems to be a problem when i tried the ... . When I put the upper ram chips back in place, ... again.

    The upper ram are not on the "OKI ... that also has the upper ram module be so kind ... Divide attempts DMA to the upper RAM and uses unusual timings ...
    gtsamour gtsamour September 2013 Hardware
  • Spectrum 48+ 4S - Upper RAM issue, and now a self-created problem!I recently picked up a known-flaky spectrum off eBay, to have a bit of fun fixing it and reliving youth. It was labelled as 'keyboard duff, shows…

    ... diagnostics said the whole of upper RAM was faulty (check all ICs ... , I've removed all the upper RAM ICs, replaced with sockets and ... .

    Given the lower RAM used to be okay, and ...
    Paulcatchpole Paulcatchpole December 2016 Hardware
  • Built a ZX Spectrum that works, but can't get the upper RAM to work?Like the title says I finished my Spectrum 3B board, and it boots, but it doesn't see the upper 32k of RAM. When it boots, the lower 16k works f…

    ... doesn't see the upper 32k of RAM.

    RAM is good, all upper RAM bad. But ... the associated logic, and RAM chips, with no effect ... direct connections between the upper RAM and associated logic, and ... 16K, or 65535 for 48K. But I tried writing ...
    DistantStar001 DistantStar001 June 2022 Hardware
  • ZX Spectrum upper RAM module (4532/4164 replacement)Following the [URL="http://zx.zigg.net/LRR/"]lower RAM replacement module[/URL], there have been quite a lot of requests for something similar for th…

    ... for something similar for the upper 32K RAM in a Spectrum.
    upper RAM module instead or one of ... of trailing wires, so the upper RAM module uses almost the same ... as the lower RAM replacement and emulates dynamic RAM.

    ...
    Zorn Zorn July 2013 Sales
  • Lower & upper ram IC's for an issue 3 please.Would any of you great folks have 1 spare lower ram, and 1 spare upper ram IC's you would be willing to sell. I'm fixing up a poorly Spectrum that is…

    ... have 1 spare lower ram, and 1 spare upper ram IC's you ...
    Your Spec-chum Your Spec-chum September 2017 Wanted
  • upper ram tacks / TR4 socket...[url="https://photos.app.goo.gl/MkqzRCuNCV3EPr9E7"]https://photos.app.goo.gl/MkqzRCuNCV3EPr9E7[/url] you can only replace that pesky TR4 so many t…

    ... would just fry the lower ram again .. this is one board ... looks like somebody attacked the upper ram with a black and decker ... .. any sugestions for replacing the upper ram tracks ?
    mark8bit mark8bit September 2020 Hardware
  • ZX Diagnostics v0.35 ReleasedHi all, I'm pleased to announce the release of zx-diagnostics v0.35, downloadable from [url="https://github.com/brendanalford/zx-diagnostics/relea…

    ... /> - Add failure beeps if a RAM issue is detected in soak ... check multiplexer ICs if all 48K upper RAM is faulty (as opposed to ...
    balford balford May 2017 Hardware
  • Repairing another Issue 2 48K Spectrum.I said at the start of the other thread that I've got another one of these and I've started investigating it. The board is more-or-less exactly the …

    ... Spectrum with its lower RAM removed and so I ... that it would work with RAM installed.

    ... at all the lower RAM socket pins look reasonable ... not be a problem with the lower RAM, but that ... get stuck. Perhaps an upper RAM problem could cause this - sadly ...
    Zorn Zorn January 2012 Hardware
  • Issue 2 Upper Ram, Loading & ResettingI have a 48k Issue 2 Speccy and for the life of me can't track down what the problem is with it. I initially thought that some of the uppe ram ic's w…

    ... thought it was Upper RAM problem but how can the problem persist across different ...
    retrogamemart retrogamemart December 2014 Hardware
  • Not bored with the Boards.Going through some old tapes stored rather badly I came across an unlikely item that that I must have stored away quickly with other low grade items …

    ... to speak with just the upper Ram problem.

    This time I ... it was retested it shower upper ram failure at IC15 ,IC16 ,IC17 ... cutting out all those remaining upper RAM chips . If it is OK ... stuff again and detected no upper RAM and suspect ICs in the ...
    harriusherbartio harriusherbartio March 2020 Hardware
  • Diagnosing Spectrum 48k (faulty RAM chip?)I have a Spectrum 48k (I believe it may be an upgraded 16k model) that doesn't work, and never has ever since the owner gave it to me. When you turn …

    I have a Spectrum 48k (I believe it may be ... load of dots in the upper-half of the screen, then ... joints for the bottom-left RAM chips seem to be ... physically on the board which RAM chip the display attributes is ... that likely to be the problem? If not, what other ...
    Muzer Muzer November 2009 Hardware
  • Looking for some 48k RAM (upper 32k bank)Greetings, I was wondering where I could find some upper RAM for a 48k (issue 4A). It's the Texas Instruments TMS4532-20NL4 P8419 (or any compatib…

    Greetings,
    I was wondering where I could find some upper RAM for a 48k (issue 4A).
    It's the Texas Instruments TMS4532-20NL4 P8419 (or any compatible RAM).

    Thanks,
    Thomas
    thomas3120 thomas3120 February 2010 Hardware
  • Spectrum 48k won't start any software but passes all RAM testsI have a rubber key 48k which will not start any software - it appears to work perfectly right up until the end of the tape and the program would sta…

    I have a rubber key 48k which will not start any ... think this was a problem with the upper RAM however on running the ... minutes. I also performed the RAM test detailed here http://www ... longer or look for non-RAM related issues?
    britain4 britain4 October 2016 Hardware
  • Repairing a faulty 48K issue 2.I am investigating one of a pair of non-working issue 2 48K Spectrums that have been sitting in a cupboard untouched for quite a few years. I haven…

    ... of non-working issue 2 48K Spectrums that
    have been ... 't narrow down
    the problem much further than I already ... looking RAS signals at all RAM chips (upper and lower).

    the upper RAM chips, which I imagine is ...
    Zorn Zorn November 2011 Hardware
  • Spectrum 48K - upper memory MIAI have recently acquired a ZX Spectrum which, according to the sticker on the bottom, should be a 48K model. It's an Issue 3 board, with upper memory…

    ... a 48K model. It's an Issue 3 board, with upper memory ... -26) installed. Here's the problem, though: apparently, the computer does ...
    unholy unholy February 2012 Hardware
  • Spectrum 48K - upper memory problemsHi I have a ZX Spectrum 48K issue 3B which does not see upper memory. On PRINT PEEK 23732+256*PEEK 23733 i got result 32767. POKE 32768,85 and PRINT …

    ... ZX Spectrum 48K issue 3B which does not see upper memory.
    problem is?
    Edward Edward May 2012 Hardware
  • Replacing Upper RAM in 48KHi Folks Well, my fun continues :) After sorting the display issues with this machine I found I couldn't load software meant for 48K machines. Havin…

    ... 't load software meant for 48K machines. Having followed the guide ... here it looks like an upper memory fault.

    Before ...
    spookt spookt July 2012 Hardware
  • 16K/48K Lower RAM (4116) replacement.You may want to read [URL="http://www.worldofspectrum.org/forums/showthread.php?t=37957"]this thread[/URL] for background information on the quest t…

    ... the lower RAM that works in all 16K/48K Spectrums ( ... column address to the RAM and so there isn ... that appear on the lower RAM address lines. In particular ... so much of a problem with later Spectrums, I ... the ZX Spectrum Lower RAM Replacement Module, pictured below ...
    Zorn Zorn May 2013 Hardware
  • Interesting 48K failureI thought I'd recount a failure I've not seen mentioned before that I saw tonight while fixing a 48K issue 6 board. The background: The initial fail…

    ... saw tonight while fixing a 48K issue 6 board.

    48K board gets shorted. TR4 is ... :
    1. A fault in upper RAM causing incorrect instructions to get ... Z80. It fixes a contention problem (basically all I/O ports ...
    Winston Winston December 2013 Hardware
  • Seriously weird Issue 2 issue... (RAM-related)Hi guys; I have been trying to fix up my Issue 2 and have run across a bizarre issue that I haven't seen elsewhere in the forums. Hopefully one of …

    ...
    Spectrum: Issue 2, 48k
    Initial problem: Yellow screen, only sees ... /> 2. MEMCHK returned 32767, upper RAM fault. UPRAM85 returned 93, so ... screen and red bars" RAM test appears, after which ... , but the same screechy problem occurs. I have another ...
    Trafferth Trafferth August 2014 Hardware
  • 48k - Why Won't it Buzzzz?Hi WOS ;) I bought a load of Spectrum games off eBay and thrown in for good measure was a 48k 1984 Issue 6a circuit board that I was told was for sp…

    ... good measure was a 48k 1984 Issue 6a circuit ... suitable components but the problem is still there and ... all work fine. The upper RAM has been removed and donated ... which now works as a 48k instead of 16k :D ... 'm guessing that the problem lies with the power ...
    retrogamemart retrogamemart September 2014 Hardware
  • 48k Stops loading and resetsI've just fixed the problem I had with my Issue 2 Spectrum only showing 16k memory by replacing all of the upper ram. With that job done I've done a …

    ... by replacing all of the upper ram. With that job done ... 65535.

    The problem is that I can load ... to load anything for 48k the speccy just don' ... screen will display with no problem, then when it gets ... still can't be the upper ram again if its returning ...
    retrogamemart retrogamemart September 2014 Hardware
  • Upper memory issueZX Spectrum 48K, issue 2, boots fine. Lower RAM OK. When tested with the new test ROM in the Diagboard, for all upper RAM tests "FAIL" is shown. I…

    ZX Spectrum 48K, issue 2, boots fine.
    Lower RAM OK.
    When ... in the Diagboard, for all upper RAM tests "FAIL" is shown.
    problem.
    IC22 is socketed two ... more important for the lower RAM, are the voltages:
    ...
    georgedb georgedb September 2016 Hardware
  • 48K Issue 2 RAM issuesI have 48K issue 2 board (I've checked, the upper memory is present!). It's not very well. I've not attempted to diagnose one before, so please bear …

    I have 48K issue 2 board (I've checked, the upper memory is ... issues are only in the upper RAM as it will actually boot ...
    kurbeco kurbeco August 2019 Hardware
  • 48k issue 4B display problem etchi,, i have a zx spectrum 48k issue 4B with a display issue it has wavy lines in both the border and paper,some colours seem worse than others ie red…

    ... ,, i have a zx spectrum 48k issue 4B with a display ... ,full re cap,disabling upper ram.it passes ram tests left in sink ...
    mark8bit mark8bit June 2020 Hardware
  • 48K Speccy Repair Log.Some people may know my love for writing up my repairs of arcade PCBs on various forums so thought I would do the same for this little fella. Had th…

    ... .

    The upper RAM, from 32KB to 64KB on ... pins, which is no problem, compared to the 128 ... not account for the initial problem.

    [IMG] ... in the byte was the problem. I tried this test ... as each of the upper RAM chips contributes a single bit ...
    Womble Womble August 2010 Hardware
  • 48k keyboard dead problemHi This is my first post and probably a problem thats been on here loads. Just been given a 48k, get the copyright screen but can't advance. I di…

    ... first post and probably a problem thats been on here loads ... />
    Just been given a 48k, get the copyright screen but ...
    zxmatt zxmatt March 2011 Hardware
<1234567…34>

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  • Looking for some 48k RAM (upper 32k bank)Greetings,<br /> I was wondering where I could find some upper RAM for a 48k (issue 4A).<br /> It's the Texas Instruments TMS4532-20NL4 P8419 (or …
  • Replacing Upper RAM in 48KHi Folks<br /> <br /> Well, my fun continues :) After sorting the display issues with this machine I found I couldn't load software meant for 48K mac…
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