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  • ZX Spectrum 48k issuesHi all! A couple of days ago I bought my first 48k Speccy off ebay (I already own a beautiful QL expanded with QubIDE interface and 640k ram). It was…

    ... timing requirements of the Lower RAM replacement module.
    [/quote]
    voltage swing ~4V minimum. Both for ...
    Trantor Trantor February 2017 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 …

    ... for the "upper" 32k byte RAM.

    With regard to ... the SRAM chip, measure the voltage on the +5V Vcc and ... into a Spectrum. If the voltage is less than 0.55V ...
    1024MAK 1024MAK March 2017 Hardware
  • Harlequin 128K minor problems.....Hi All, I've just assembled my Harlequin 128K kit, I had initial problems with it that I traced to not having soldered all of the pins on a couple…

    ... a bit sensitive to the RAM brands as I found.
    voltage drop on the 5V line ...
    ingo ingo March 2017 Hardware
  • Disabling the ROM without removing the whole thingHi! I've got my hands on a non-working issue 6a. I suspect the ROM may be bad, but other things may be faulty as well. I've read that in an otherwis…

    ... />
    - The lower RAM is replaced with a PCB ... with another known working lower RAM PCB (from zigg.net ... Removed one of the upper RAM chips (IC15) and there was ... could do (the lower RAM chips are no longer ... the way, the 7805 voltage regulator was changed to ...
    Mikelone Mikelone April 2017 Hardware
  • ZX Spectrum Test PCB I recently read about one of these (I think it may have been the Retroleum site but I am not sure) and I thought "What a great idea" . As pictured …

    ... .uk/2014/11/zx-spectrum-voltage-regulator.html"]blog.tynemouthsoftware.co ... .uk/2014/11/zx-spectrum-voltage-regulator.html[/url]

    RAM chip socketed . This must mean ...
    harriusherbartio harriusherbartio May 2017 Hardware
  • Repair ZX Spectrum +2 black issue 1Hi all, after a long time i will try to repair a ZX Spectrum +2 black i found the last days i know for sure that CPU is damaged (already repla…

    ... i have already order some ram chips to check

    RAM chip and i will check ... +5 Vcc voltage on the ram chips but not Vss voltage, is that ...
    xaris_sm xaris_sm June 2017 Hardware
  • ROM emulation in softwareHi, first of all -- I only have shallow / uni knowledge of hardware, electronics, and physics. So forgive me for asking things that are out of that …

    ... with lots of pins, TTL voltage, and without any other hardware ... lots of pins, and 64KB RAM. Is there a microcontroller that ...
    tstih tstih June 2017 Hardware
  • ZX Spectrum 48K it only shows colored barsHello, I'm new to the forum and I need help with a ZX Spectrum 48K which I bought recently unfortunately defective. I want to mention that before t…

    ... the ULA that reads the RAM is faulty, the CPU should ... write to the 4116 "lower" RAM. So when it detects a ... , the heatsink of the 7805 voltage regulator), using a test probe ...
    1024MAK 1024MAK August 2017 Hardware
  • 48k Issue 6a Very sick indeed.Hi Guys. I have a 48k Issue 6a board that shows a white screen with grey border. The white screen has three black squares spaced equally on the le…

    ... /> [quote="RSwipeCA;55309"]My lower RAM voltages are -5V = -029.5mV ... are way off. If the voltage regulator, capacitors, and TR4 and ... chips (all the 4116 "lower" RAM chips and I recommend removing ... the 4116 (or equivalent) "lower" RAM chips back in. Then power ...
    1024MAK 1024MAK October 2017 Hardware
  • 48k Issue 6a Very sick indeed.Hi Guys. I have a 48k Issue 6a board that shows a white screen with grey border. The white screen has three black squares spaced equally on the le…

    ... br /> I desoldered all the RAM chips and socketed them. I ... these voltages at the lower RAM sockets -5v = -4.84v, ... jumps erratically on the supply voltage, almost like a intermittent short ... on the board, immediately, the voltage started jumping about again.
    RSwipeCA RSwipeCA October 2017 Hardware
  • Troubleshooting my +2To put this in context: a while back (i.e. late last year and earlier this year) I was looking to put together a compilation of modern Spectrum games…

    ... load (the computer), the output voltage will be greater than the ... crashes caused by the wobbling RAM packs.

    Still, this ...
    The Mighty Dopethrone The Mighty Dopethrone October 2017 Hardware
  • Troubleshooting my +2To put this in context: a while back (i.e. late last year and earlier this year) I was looking to put together a compilation of modern Spectrum games…

    ... .5V on load. The unloaded voltage can be higher...

    voltage regulator getting rather hotter than ... , note that, some third party RAM packs for the ZX81 require ... modifications done, may damage their RAM if the "9V" input is ...
    1024MAK 1024MAK October 2017 Hardware
  • Troubleshooting my +2To put this in context: a while back (i.e. late last year and earlier this year) I was looking to put together a compilation of modern Spectrum games…

    ... expansions I had was the RAM Turbo and a Currah Microspeech ... 's as long as the voltage and current are sufficient and ...
    ivanb303 ivanb303 October 2017 Hardware
  • Troubleshooting my +2To put this in context: a while back (i.e. late last year and earlier this year) I was looking to put together a compilation of modern Spectrum games…

    ... I had was the RAM Turbo and a Currah ... as long as the voltage and current are sufficient ... 5V on load. The unloaded voltage can be higher...
    ... outputs a loaded output voltage of 10.5V or ... the heatsink for the 7805 voltage regulator getting rather hotter ...
    The Mighty Dopethrone The Mighty Dopethrone October 2017 Hardware
  • Nasty vertical pattern on a 128K Toast Rack via RGBI managed to fix the busted membrane on my [url="https://www.worldofspectrum.org/forums/discussion/55755/got-myself-a-128k-toast-rack-plus-a-simple-a…

    ... capacitors next to a few RAM chips. The patter became even ... upside, smoothing out the supply voltage does have an appreciable effect ...
    Ast_A_Moore Ast_A_Moore January 2018 Hardware
  • Trying to repair my old 48kAbout 30 years ago I had a spectrum 48k, it had some troubles in the end, it was very unstable when it was cold, so I had to warm it up an hour befor…

    ... measured the voltages on the RAM chips..

    Pin 1 ... converter circuit only produces a voltage of about -4.5V to ...
    1024MAK 1024MAK April 2018 Hardware
  • help with issue 3 48k speccy after recap and new tr4 and tr5I have a 48K speccy that was not working. After recapping and replacing TR4 and TR5 it came back to life However after a short while running weird …

    ... TR5 die, as the 7805 voltage regulator suppliers the +5V. However ... -5V.

    The 'lower' RAM chips (type 4116 or equivalent ... present can damage the 4116 RAM chips.

    The symptoms ... likely caused by a faulty RAM chip.

    The ...
    1024MAK 1024MAK July 2018 Hardware
  • Replacing voltage regulators - need to sanity check a few things pleaseHi Everyone I'm in the process (with a lot of help from some friends at Greenford Computer Club), of giving my three Speccys some much needed prev…

    ... successfully replaced all the 5v voltage regulators in all three machines ... to be something more (probably RAM, CPU or ULA related).
    chrisgreen chrisgreen May 2019 Hardware
  • Does Survivisection load & play on a real +2a?Hi All, My apologies, another question.. Would someone with a DivMMC and a +2a be able to confirm whether Survivisection runs and plays on it? …

    ... a failure of the voltage regulator caused the RAM chips to fry ... they were caused by damaged RAM chips. It has been long ...
    Alessandro Grussu Alessandro Grussu June 2019 Hardware
  • Does Survivisection load & play on a real +2a?Hi All, My apologies, another question.. Would someone with a DivMMC and a +2a be able to confirm whether Survivisection runs and plays on it? …

    ... a failure of the voltage regulator caused the RAM chips to fry ... they were caused by damaged RAM chips. It has been long ...
    AD-RS1600i AD-RS1600i June 2019 Hardware
  • Another Spectrum is brought back to life.Hi Spec-chums. I have been having bit of busy afternoon with repairs today. I've brought back to life a Panasonic Super-VHS recorder, and more intere…

    ... use a multimeter on the voltage range to test the various ... it could still be a RAM fault.

    If you ... that there is a lower RAM fault.

    Note that ...
    1024MAK 1024MAK August 2019 Hardware
  • What % of WOSSERS use "old school" tape loading when playing their Speccy games.My guess is .000000001% ( but I might be slightly out on this! ) Do people still enjoy doing it "the old way"?

    ... a 7805 three terminal voltage regulator chip. This takes ... , ULA, ROM, upper RAM and the logic chips all ... difference between the input voltage to the 7805 and ... heat that the 7805 voltage regulator in the ZX ... replace the existing 7805 voltage regulator with a mini ...
    1024MAK 1024MAK September 2019 Chit chat
  • Spectrum 128k advice neededHi, I'm new to this forum and the spectrum world. I have this spectrum "toastrack" that was working fine until today. It doesn't boot anymore, it s…

    ... probe.

    Also voltage to the RAM chips is 4.95V ...
    gleegum gleegum July 2020 Hardware
  • Bit of fun - one change onlyI also posted this on another marque's forum (for their products) to see. Its just a bit of fun really. OK, if you could of made one change to a S…

    ... , the heatsink for the 7805 voltage regulator was moved from the ... (bank/page) any of the RAM (unlike in the earlier ZX81 ...
    1024MAK 1024MAK July 2020 Hardware
  • General PSU repair guidesNot Speccy related. I'm just looking for a guide as such as to where to begin with a power supply repair. Realise this is a bit of an odd thing to as…

    ... the points you make about ram etc are what I'd ... of carefully probed the "low voltage" half of the power board ...
    spider spider August 2020 Chit chat
  • doubt about swapping ULA in an issue 2 boardIs it possible to swap a 6C001E-6 ULA type with a 5C112E ? I have this issue 2 board that is not booting, it shows me a black border with horizont…

    ... but DiagROM gives me lower RAM errors, it says all ... 7805.

    RAM IC's are MM5290N
    I replaced just one RAM with a modded 4164 ( ... shows me an entire lower RAM failure.

    ... to look to test for voltage drop culprit.

    gleegum gleegum September 2020 Hardware
  • Quirky nerdy hardware quiz time[b]Quirky nerdy hardware quiz time[/b] [list=1][*]How many transistors are on the issue one ZX Spectrum PCB? [color=#FFFFFF].[/color] [*]Which d…

    ... tell me the normal forward voltage of a blue one. ... Spec-chum for giving the voltage as approximately 3.2V ... that has a non-functional RAM chip soldered on to ... 64k bytes or less of RAM. So bonus points to ... amount of unique (unduplicated) RAM (as seen by the Z80A ...
    1024MAK 1024MAK December 2020 Sinclair Miscellaneous
  • Emulator compatibility with real SpectrumHi emulator programmers... Having spotted for the last 6 months that my iPAQ is still missing a Spectrum emulator I started typing last tuesday - an…

    ... the lower part of the RAM is slower because of the ...
    Anders Anders September 2001 Emulators
  • spectrum problemshello, I just recieved a spectrum 48k on ebay [img]/__forums/images/smiles/icon_smile.gif[/img] (I live in the U.S.) I have a transformer to conver…

    ... a transformer to convert the voltage from 120 to 220.
    thoma thoma January 2002 Sinclair Miscellaneous
  • Thanks for the memories... is it 16k or 48k? Hi. At three different flea markets in Gothenburg, Sweden I found just as many Spectrums... (and a ZX81! [img]/__forums/images/smiles/icon_smile.gif…

    ... out the size of their RAM-memory?

    Most basic ...
    Lars Lindblad Lars Lindblad January 2002 Sinclair Miscellaneous
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HitBox

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ram 12.6K 21.4K
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