-
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... ) are all present at the lower RAM ICs (the 8 in a ... row on the lower left). I put the 4116 ... -
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... what appears if all the lower RAM ICs are removed.
lower RAM arrangement. -
Dark Screen, non working 48k Spectrum (rubber key)I have an issue 1 (I think) "dead cockroach" 48k Spectrum. On power up I get a dark screen and the machine is unusable - see pics. Any ideas on the…
... happens when there is a lower RAM fault. Are all the supply ... -
Would things of been better if the NMI was fixed ?I was just wondering, if the NMI bug was fixed say early on in production, so for instance all issue twos (and late issue ones) and beyond had the "f…
... a more sophisticated ROM (and RAM) paging protocol and hardware would ... with the display hardware) the lower RAM. But of course, there are ... -
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... , I always remove all the lower RAM first.
If then any ... /> After that I test the RAM ICs for short circuit.
Ater that I replace the RAM ICs one by one, checking ... />
If any of the RAM ICs fails, then I always ... -
Wanted: Working 48K MotherboardMy Issue 3 48K motherboard is kaput, so I'm after a replacement. I've already fitted the case with a new membrane, so I don't need a whole new system…
... faults. I've desoldered the lower RAM ICs so far (no mean ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
... Blow
2. 4116's (lower ram) go bad
2. After ... />
Check your voltages on lower memory. -
Wanted: Working 48K MotherboardMy Issue 3 48K motherboard is kaput, so I'm after a replacement. I've already fitted the case with a new membrane, so I don't need a whole new system…
... faults. I've desoldered the lower RAM ICs so far (no mean ... -
4116 replaced by 4164 - "Noisy" paper?After I replaced my 4116's with 4164's and hooked them up to +5V, disconnected -5V and +12V, I have what looks like vertical lines in the paper, like…
... Z80 CPU (which has much lower output impedance than the old ... to be able to read lower RAM at the same time that ... the CPU was using upper RAM - because using resistors was way ... will cause CPU writes to lower memory and the ULA fail ... -
4116 replaced by 4164 - "Noisy" paper?After I replaced my 4116's with 4164's and hooked them up to +5V, disconnected -5V and +12V, I have what looks like vertical lines in the paper, like…
... feed my memory modules. As lower ram is what makes up the ... -
Using an ATX power supply - Spectrum 48kOK... I have an Issue 3 48K model and the DC-DC converter does not work and I can?t make it work. :( There is a MOD to use an ATX power supply on the…
... -DC circuit goes, often the lower ram gets fried too. Which is ... -
Using an ATX power supply - Spectrum 48kOK... I have an Issue 3 48K model and the DC-DC converter does not work and I can?t make it work. :( There is a MOD to use an ATX power supply on the…
... -DC circuit goes, often the lower ram gets fried too. Which is ... -
Issue 4S Schematics and DC-DC circuitA while ago I bought a Spectrum 4S that had problems tuning. I removed the RF tuner as I was not going to use it and did the composite mod. It worked…
... overvolting of course had killed lower ram. So I desoldered the DRAM ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
You have checked that you have -5V +12V and +5V on the lower ram (4116's) and +5V on the high ram?
CHeck the spectrum repair guide on this site, is very useful. -
Issue 4S Schematics and DC-DC circuitA while ago I bought a Spectrum 4S that had problems tuning. I removed the RF tuner as I was not going to use it and did the composite mod. It worked…
... overvolting of course had killed lower ram. So I desoldered the DRAM ... -
Issue 4S Schematics and DC-DC circuitA while ago I bought a Spectrum 4S that had problems tuning. I removed the RF tuner as I was not going to use it and did the composite mod. It worked…
... do with noisy voltage to lower ram. Need to investigate this when ... -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
I have no ROM analyser or logic analayser.
I have tried many times but it would't initilase. Is there ar way tho check lower RAM chips or to disconnect upper RAM.
Is there are way to bring it working or can I throw it away. -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
... ar way tho check lower RAM chips or to disconnect ... upper RAM.[/QUOTE]
The upper RAM chips are ... are often due to failed lower RAM, but it's a ... on screen.
Lower RAM checking is a matter of ... add-on test card with RAM test & LEDs ... -
Spectrum 48K help neededI hav got an old Specrtum 48K issue 3. When I plug-in power connector it doesn't show the home screen (c) Sinclair.... From about 50 times trying to …
[QUOTE=RetroTechie;636321]Lower RAM checking is a matter of ... add-on test card with RAM test & LEDs to indicate ... a logic analyser. If the RAM is detected as bad by ... -
48k+ CPU SocketThink I've bitten off more than I can chew... After the desoldering my z80 went without incident, no damaged pads, tracks etc. I expected the socket…
... (74LS154s) etc.
If lower ram has been connected all this ... one or more of the ram chips of lower ram is dead. -
Issue 2 Failed 48k to 128k upgradeI have been trying to upgrade my Issue 2 with the help of Velesoft, using this schematic; [IMG]http://i764.photobucket.com/albums/xx284/arioch1973/4…
... oscilloscope that signals are reaching lower ram on the right pins.
Lower ram simply is not usable to ... -
Issue 2 Failed 48k to 128k upgradeI have been trying to upgrade my Issue 2 with the help of Velesoft, using this schematic; [IMG]http://i764.photobucket.com/albums/xx284/arioch1973/4…
... Issue 2 16k machine (replace lower ram with 4164s asap since I ... -
Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... , I always remove all the lower RAM first.[/quote]
If ... -
16k Issue 2 board and DivIDE load errorsI today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from …
... socketed 4164s in place for lower ram. I can take a photo ... -
16k Issue 2 board and DivIDE load errorsI today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from …
... with socketed CPU, ROM and Lower RAM (4164s I find to be ... -
16k Issue 2 board and DivIDE load errorsI today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from …
... , put 4164's as low ram (cutting -5V and +12V track ... +12V used to connect on lower ram). Put logic chips and 4164s ... as high ram. Add a buffer transistor to ... -
Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
... . However when measuring A7 on lower ram the signal is remaining on ... wave signal like on higher ram A7.
Perhaps this ... -
Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
... pins on one of the lower ram sockets through a tiny bit ...Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
... pins on one of the lower ram sockets through a tiny bit ...
