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Faulty Issue 1Hi all, thought I'd document my efforts in getting another speccy working. I've never done this before so please bear with me... I recently took a p…
... certain that, with the lower RAM module installed, the computer ... corruption; CPU use of the lower RAM is not affected.
... addressing one; sometimes the lower RAM module latches an incorrect address ... this problem when the lower RAM module is used. I ... -
NTSC Compatibility?Correct me if I'm wrong, but wasn't the Timex 2068 the only NTSC clone built of the ZX Spectrum? And I use clone lightly... From what I underst…
... O port address that does not have any device at that ... the data bus for [the lower RAM and ULA] and the CPU ... is reading data from the lower RAM, a I/O read by ... at the same time will not return FF hex, but whatever ... to be reading from the lower memory for use in ... -
NTSC Compatibility?Correct me if I'm wrong, but wasn't the Timex 2068 the only NTSC clone built of the ZX Spectrum? And I use clone lightly... From what I underst…
... only reads data from the RAM when it needs said data ... , the ULA does not read any data from the RAM.
The ... when the CPU addresses the lower RAM, or certain I/O ports ... -
Sudden death of ZX Spectrum 48KHello A friend gave me a 48K rubber keyed Spectrum. I brought it home, hooked it up to my little TV and powered it up. I was very happy to see t…
The problem might be the lower RAM or ULA judging by the ... prone to failure. I'm not a hardware expert though so ... -
Sudden death of ZX Spectrum 48KHello A friend gave me a 48K rubber keyed Spectrum. I brought it home, hooked it up to my little TV and powered it up. I was very happy to see t…
... . It's to allow OKI RAM to be used as upper ... for TI or OKI upper RAM.
Check for a ... coil. TR4 very often (though not always) fails with a short ... one or more of the lower RAM ICs. It's a very ... now where more often than not one will give up within ... -
Composite picture qualityI have read many many discussions here about the composite video modification of the Spectrum 16/48K models. I have choosen one of the simplest comp…
... I have the upper and lower ram modules installed (in my case ... in some way? Should it not be earthed? -
Composite picture qualityI have read many many discussions here about the composite video modification of the Spectrum 16/48K models. I have choosen one of the simplest comp…
... have the upper and lower ram modules installed (in my ... These use modern SRAM chips, not old DRAM chips. That ... some way? Should it not be earthed?[/quote]
... earthed! The PSU does not have an earth wire... ... / DC ground would not make any difference either.< ... -
Testing 4116 type DRAMsHappy New year All! I'm managed to find some time to repair some more Spectrums :) woo hoo. I have a couple with busted lower RAM, Sooo, I appr…
... applied first (and removed last!). Not [i]quite[/i] sure, but ... ]If not, is it feasible to actually make a ram module replacement ... 64K*4 DRAMs, or a lower RAM replacement module. -
Unresponsive Spectrum with Magenta border.This Spectrum is taking an age for me to repair, thank for all the help thus far! So after I switch on the ZX Spectrum+ I get the familiar white…
Thanks, not what I wanted to hear! :)
However I swappned the ULA to a known good one and it still did the same thing, the ULA in the other rmachine worked fine :)
So I wonder if the lower RAM is still borked? -
Issue 4A, tests complete fine but get odd crashing problemHi all, I've got an issue 4A which has had all of its lower RAM replaced, TR4, TR5 as well as its CPU. It originally had quite high voltages (20-3…
... all the joints on the lower RAM, CPU and caps (I recappped ... /TR5 was replaced or not. My own RAM is clearly a bit ... an error. I ran the RAM test again after Manic Miner ... -
Need some help repairing an issue 3 spectrumI am looking for some help repairing an issue 3 speccy, here's what I tried so far. The speccy is not booting up correctly, when using the diagnos…
Yep, as Mark says, check the voltages first. If they're not as expected, don't run the machine longer than is absolutely necessary as the lower RAM may become further damaged.
B -
Need some help repairing an issue 3 spectrumI am looking for some help repairing an issue 3 speccy, here's what I tried so far. The speccy is not booting up correctly, when using the diagnos…
... ="patzik;873311"]Actually with the lower ram removed the picture should be ... you'd expect if all RAM was removed would indicate to ... me that the issue is not with the data bus separation ... -
Need some help repairing an issue 3 spectrumI am looking for some help repairing an issue 3 speccy, here's what I tried so far. The speccy is not booting up correctly, when using the diagnos…
... spectrum I tried without the lower ram. This video is exactly the ... you said.
With the lower ram installed all ic's test ... this line to test faulty, not all don't you think ... adressing, I'll reinstall the lower ram and do some more testing. -
Need some help repairing an issue 3 spectrumI am looking for some help repairing an issue 3 speccy, here's what I tried so far. The speccy is not booting up correctly, when using the diagnos…
... spectrum I tried without the lower ram. This video is exactly the ... you said.
With the lower ram installed all ic's test ... this line to test faulty, not all don't you think ... adressing, I'll reinstall the lower ram and do some more testing ... -
Best place to start learning assembly on WOS ?So I'm pretty new at this forum but not the Speccy so my BASIC is pretty good. I can see lots of resources on WOS for doing machine code/assembly but…
... ) (***) / 16384 (start of display ram) without understanding where the numbers ... function; clearly that's not true and for an absolute ... in decimal.
(***) Not seeing the AY ports 65533 and ... 8-bits ($fd) do not change. This somewhat simplifies the ... -
ZX Spectrum issue 4B acquiredI recently acquired a ZX Spectrum with serial number 138-363292 on the case, and a 1983 issue 4B board I got it for the purpose of repair. and have…
After Initial tests things are not looking too good. have ordered ... like there may be damaged lower ram (seems 2 may have been ... installed in the case, and not pulling it out again with ... -
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…
... , but the DRAM chips are not responding correctly to the 128 ... . You could try changing the RAM type selection links. Suggest the ... of lower RAM is only refreshed by the ULA. The Z80 is not ... -
help with my original issue 3b from when i was a teen. possible lower ram fault.hello, well ive tried to fix my old speccy, but haven't made much progress. could you help me out with some diagnosis. the fault occurred about…
ive been told it cold be the rom or cpu. as generally lower ram faults result in vertical lines and not able to type anything. -
help with my original issue 3b from when i was a teen. possible lower ram fault.hello, well ive tried to fix my old speccy, but haven't made much progress. could you help me out with some diagnosis. the fault occurred about…
Video does not work for me :-(
All the RAM chips are DRAM type. In ... byte of the lower RAM working. It will not then get to ... variations of symptoms of a RAM fault. The problem with ... may or may not be a RAM fault. But RAM faults and ... -
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…
... are two masters of the "lower" RAM, the CPU reads and writes ... it tries to access the lower RAM at the same time.
lower RAM. If the connections are okay, and it's not the ... , that points to the lower RAM replacement module not being fully compatible with ... -
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…
... not happy with the !RAS or !CAS timing requirements of the Lower RAM ... -
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…
... not happy with the !RAS or !CAS timing requirements of the Lower RAM ... ) that separate ULA/lower RAM from ROM/upper RAM/Z80 data lines, may ... need adjustment when a lower RAM replacement module is used. Probably ... -
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…
... not happy with the !RAS or !CAS timing requirements of the Lower RAM ... -
What are the differences between the +2 and the +2A ?I only acquired a +2 for the first time in my life a few months ago. It works fine. :) I even managed to tracke down nearly all the wargames by the s…
... computers from the 1980s were not well documented to the levels ... ZX Spectrum 48k model was not really designed with any possible ... . One set replaced the 4116 "lower" RAM which includes the scree, so ... set replaced the 32k "upper" RAM chips, which is of course ... -
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…
... lower pin 3 to lower pin 25 in the edge connector does not ... />
- The lower RAM is replaced with a PCB ... with another known working lower RAM PCB (from zigg. ... Removed one of the upper RAM chips (IC15) and there ... could do (the lower RAM chips are no longer ... -
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…
... to the RAM chips. Some of the schematics may therefore not be ... the Z80 CPU and the lower RAM, so worth testing these. You ... the ULA that controls the lower RAM. And the ULA responds to ... you power up without a lower RAM module fitted?
[b ... -
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 module is removed I get something similar (not exactly the ... -
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 …
... and said "lower Ram OK" then "Upper Ram OK" . I could not do any ... think it shows I have not damaged anything replacing the caps -
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 …
... what happened next.It displayed:-. Lower RAM faulty $7FFC : and then : ... Upper RAM error XP SFFFF ADSDF : 76543 ... . Cannot proceed further both lower and upper RAM faulty .
... this time the lower RAM was OK , but not when I ran ... -
ZX Spectrum spare parts : "endangered" and functional "extinctions" only It struck me how some Spectrum spare parts or parts that were used with Spectrums and that were commonly available are no longer available . The em…
... on this list it should not be on the MAIN list ... (at least not in exactly the same form ... />
2) Drop in Replacement Lower RAM Chips (4116-150's
