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Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... out where physical RAM finishes. It is not a full ... needs an area in RAM to store return addresses ... will be in the "upper" RAM (if it is a ... code does not need to use the "upper" RAM. So sometimes ... copyright display before the "upper" RAM fault causes the CPU ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... , it will be in the "upper" RAM (if it is a 16k ... initialization code does not need to use the "upper" RAM. So sometimes the ... the copyright display before the "upper" RAM fault causes the CPU to ... /> Maybe easier to just disable upper RAM ? -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
To disable the "upper" 32k of RAM, take a piece ... . That will disable the "upper" RAM, as the CAS signal won ... 't reach the RAM chips.
Credit ... be changing whether or not the CPU is executing ... CPU is accessing ROM or RAM.
The data ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... ;764963]To disable the "upper" 32k of RAM, take a piece of ... +5V. That will disable the "upper" RAM, as the CAS signal won ... 't reach the RAM chips.
[I ... with IC 23 but still not getting the white copyright screen ... -
Spectrum Not Responding to Keyboard InputHello, sorry if this thread is not in the correct place, This is my first post and I'm not sure where to post this type of thread. :lol: Anyway, I r…
... some wire to disable the upper ram chips on the spectrum and ... is the computer is still not responding to any input from ... Spectrum with 16K of RAM however this did not fix the problem ... normally, however when trying the Upper RAM test the border always appeared ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... OR gate chip. It is not a multiplexer, however the logic ... chip is not fitted, the "upper" 32k DRAM chips will not work.
upper" RAM (as the CAS signal won ... first byte of the "upper" 32k of RAM returns.
Now ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... gate chip. It is not a multiplexer, however the ... is not fitted, the "upper" 32k DRAM chips will not work.< ... can then disable the "upper" RAM (as the CAS signal ... installed a switch. (did not have a real switch so ... IC 23.
Does not work, no keyboard no ... -
48K: Half of copyright message in the middle of the screen?!Issue two. Has 74LS08 over the Z80, but the ULA is 5C112E-3 (I think this should be a 5C102E??? - I have one, but I'm not sure if it is working, at l…
... 's replaced the ULA but not removed the 74LS.
upper RAM chips socketed? If so, and ... -
Spectrum Plus display issueHi, does anyone know if this is fixable at all by someone with no experience? From looking on a similar post on World of Spectrum forum they mention…
Faulty lower RAM could be preventing the CPU ... almost always caused by faulty upper RAM. It seems that a failed ... its output when it's not supposed to.
I ... -
Spectrum Not Responding to Keyboard InputHello, sorry if this thread is not in the correct place, This is my first post and I'm not sure where to post this type of thread. :lol: Anyway, I r…
... enough in the RAM test pattern for the upper RAM there was no ... only have a few left! Not sure what to do when ... -
48K: Half of copyright message in the middle of the screen?!Issue two. Has 74LS08 over the Z80, but the ULA is 5C112E-3 (I think this should be a 5C102E??? - I have one, but I'm not sure if it is working, at l…
... into the first byte of upper RAM (01010101 and 10101010 respectively). ... determine with reasonable confidence which upper RAM chip(s) have failed.< ... br /> One thing is not completely clear, but it might ... more specific a potential broken upper memory chip, by just ... -
48K: Half of copyright message in the middle of the screen?!Issue two. Has 74LS08 over the Z80, but the ULA is 5C112E-3 (I think this should be a 5C102E??? - I have one, but I'm not sure if it is working, at l…
... br /> One thing is not completely clear, but it ... specific a potential broken upper memory chip, by just ... bit position for all of upper RAM (e.g. IC22 ... , the first byte of upper RAM (as you say) will ... 65535.
An upper RAM chip might have failed in ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... think we still have an upper RAM issue to resolve.
not responding to keyboard input) when one of the 4532 upper RAM IC ... -
48K: Half of copyright message in the middle of the screen?!Issue two. Has 74LS08 over the Z80, but the ULA is 5C112E-3 (I think this should be a 5C102E??? - I have one, but I'm not sure if it is working, at l…
... can test either all of upper RAM or just a small area ... of lower RAM. It stripes a random sequence ... most of the common Spectrum RAM faults.[/QUOTE]From this site ... -1.tzx[/URL]
{Not my code by the way ... -
48K keyboard issue48K issue 3b reads keys without... keyboard. Looking at recorded keys, problems seems to be with one data line - D1. It happens after a while since p…
Hmm, why not simply disable the upper RAM and continue tracking down the ... -
48K keyboard issue48K issue 3b reads keys without... keyboard. Looking at recorded keys, problems seems to be with one data line - D1. It happens after a while since p…
While disabling the "upper" RAM does not isolate it from the data lines, given how easy and quick it is to solder a wire on to disable the "upper" RAM, I think it is still worthwhile as a next step.
[B][I]Mark[/I][/B] -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
Are all upper memory IC's socketed at ... could try removing all the upper RAM, and reintroducing it one IC ... not, you could try the same troubleshooting methods as with lower RAM ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... QUOTE=balford;776008]Are all upper memory IC's socketed at ... could try removing all the upper RAM, and reintroducing it one IC ... not, you could try the same troubleshooting methods as with lower RAM ... />
B[/QUOTE]
Not on sockets, yet.
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
Checked upper ram with an oscilloscope and can not find any signals that look ... a question why we should not use IC25, IC26 74LS157 from ... TI.
But is that not the same thing as NS ...RTC module for DIVIDE[IMG]http://velesoft.speccy.cz/other/rtc_module_v01_full_top.jpg[/IMG] [IMG]http://velesoft.speccy.cz/other/rtc_module_v01_full_bottom.jpg[/IMG] [IMG…
... ram
OR A ;reset carry (NC) if joypad is detected
not detected then reset state of all ... joy port
SCF ;joypad not detected then return with carry (C ...New user with a dead 48k issue 2Hello all I've found my way here from watching some excellent youtube videos by Joulesper Coulomb in an attempt to fix a issue 2 rubber key 48k I bo…
... I suspect either lower or upper RAM has gone bad (and I ... pump/braid)?
If not, sending it off for repair ...ZX Spectrum 48K AV IssueOK so I dugout my old 48K Speccy today and decided to AV mod it. I did the mod (pretty easy) but the picture I am getting is this. [url=http://posti…
Ok, that's upper RAM so wouldn't have any ... can be used to replace upper RAM.
Bverstee on here ... the past - the ULA is not the correct type (should be ... to replace IC19 (top right upper RAM chip), and the screw holding ...Help put this back to 16kSo this issue 2 arrived today and ive opened it up just to nosey and confirm that infact it is an issue 2. Now from the help offered in an earlier po…
... few connections so that OKI RAM will work. The issue ... default only supports TI RAM for the upper RAM.
... 16K Spectrum (I'm not sure why you'd want ... this), remove all the upper RAM ICs along with whatever is ... just one of the upper RAM ICs will do the ...Help put this back to 16kSo this issue 2 arrived today and ive opened it up just to nosey and confirm that infact it is an issue 2. Now from the help offered in an earlier po…
... the CPU, but not always. Next to the upper RAM is another common ...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 …
... />
1. The other (original) upper RAM chips are 4532-20NL3. The ... are 4164B-15. I'm not sure if all the chips ... such as a Kempston or RAM Turbo interface.
3. After ...Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... working, and any failed RAM is not holding any data lines low ... failure is in lower or upper RAM depending on the pattern.
Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... working, and any failed RAM is not holding any data lines low ... failure is in lower or upper RAM depending on the pattern.
Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... 12V to run the lower RAM - this means the voltage ... to remove all the lower RAM chips anyway, so personally ... to make sure you've not left any solder splashes ... , that's POINT ONE - not one) of a volt. At ...
If it fails, then upper RAM, CPU/ROM can be swapped ...Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... 12V to run the lower RAM - this means the voltage ... to make sure you've not left any solder splashes ... , that's POINT ONE - not one) of a volt. At ...
If it fails, then upper RAM, CPU/ROM can be swapped ... I'll remove the lower ram, check the voltages, fit ...RAM issue for potential 48k buy?Hi guys I've got a 48k in my sight for ?20 but... it has an issue: [QUOTE]"I tested the computer and only displayed a distorted screen. Coloured …
... ]
I'm not too familiar with the ZX ... .jpg[/IMG]
Not sure if its worth salvaging ... was going to use the upper ram slots sockets as a donor ... my 48k if the lower RAM ever went wrong on ... enough anyway...
not sure... :-?
