-
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. …
... 16K Spectrum. This usually indicates a fault with the upper RAM ... passed from testing lower RAM to upper RAM. Here is an ... first read from the upper RAM location retrieved the decimal ... capture the RAM-FILL routine passing from lower RAM to upper RAM, but ... -
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 ... you want to upgrade a 16K Spectrum and will need the ... -
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…
... It booted okay as a 16k when I tried it, ... of 16k. The tape version of Balford's ram test ... said the whole of upper RAM was faulty (check all ... I've removed all the upper RAM ICs, replaced with sockets ... />
Given the lower RAM used to be okay, and ... -
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…
... the upper 32k of RAM.
When it boots, the lower 16k ... , tells me that lower RAM is good, all upper RAM bad. But the ... all direct connections between the upper RAM and associated logic, and I ... -
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 -
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 …
I got my new upper ram replacement module from Zorn ... . 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 ... attempts DMA to the upper RAM and uses unusual timings ... -
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…
... some of the uppe ram ic's were faulty ... went on to desoldered the upper ram ic's, socketed the ... board and replaced the ram with known good chips. ... replaced all the upper ram with known good ram from another Issue ... cant now be the upper ram as I swapped and ... -
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 ... -
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 ? -
A tally on the number of successful builds of the Harlequin[SIZE=4][COLOR=Green][U][B]A tally on the number of successful builds of the Harlequin.[/B][/U][/COLOR][/SIZE] Please post your successes below :-) …
... /> Also 16k games appear to play fine. Ran 3 different ram checking ... utils. One of them reports upper ram failure every time with Z84C0008 installed ... -
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 address connections for OKI RAM when the appropriate link ... if I remove the socketed upper RAM chips and power it up ... powering it up without the upper RAM chips in place wouldn't ... out upper RAM failure if the Spectrum initializes and works as a 16K machine ... -
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 …
... it was retested it shower upper ram failure at IC15 ,IC16 ,IC17 ... So basically it is a 16k Spectrum . I will reassemble ... further tests as a 16k machine . I do ... upper RAM chips . If it is OK as a 16k ... something had caused lower RAM failure this time What a ... -
Black screen on 48k+Hello peeps Just bought a 48k+ was working fine then after leaving it off over night I turned back on to get a total black screen, no border etc. …
... and seems to be an upper ram failure. ICs 15-22 apparently each ... easier way of finding which ram chip is responsible? Also. How ... -
48k black paper white borderI recently sold a speccy to a guy, unfortunately the power supply didnt survive the trip, so on replacing for him it seems neither did the speccy! H…
... see it causing a lower RAM failure as there wouldn't be ... causes knock on effects to RAM voltages etc.
I ... a day then suffer an upper RAM failure!
B -
48K Issue 2 Spectrum showing exactly 16KI've acquired an issue 2 and it quickly became clear that only 16K of memory is available. I've read that some early 48K Spectrums with malfunctionin…
... . So for the "upper" 32k bytes of RAM, you need eight chips ... eight bits wide. If one "upper" 32k DRAM chip fails completely ... link to disable the "upper" 32k bytes of RAM, but either LK3 ... sell machines with non-functional "upper" RAM as 16k byte machines. It's ... -
How can I fix a problematic Retroleum Smart Card. I did not do anything "WRONG " with it but I did but it on a flexible cable and this seems to have "upset" it .Since then It does not perform the …
... this . It said lower RAM was OK . Upper Ram failure at $FFFE .Then it ... . The colour palette test confirms upper RAM error encountered . Suspect IC21. IC ... IC21 and what caused the failure ? Does it need a recap ... -
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 -
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…
... blow the entire lower 16K of RAM in one go. On ... .
The upper RAM, from 32KB to 64KB on ... BTS 8 means that the failure pattern is 8 in hex ... as each of the upper RAM chips contributes a single bit ... fault will wreck the upper 32KB totally, leaving only ... -
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…
... I'd recount a failure I've not seen mentioned ... />
The background: The initial failure was caused when a peripheral ... br /> 1. A fault in upper RAM causing incorrect instructions to get ... new hypothesis:
5. Failure of TR6
Now ... -
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 …
... problem: Yellow screen, only sees 16k.
Abbreviations in narrative ... .
2. MEMCHK returned 32767, upper RAM fault. UPRAM85 returned 93, so ... "black screen and red bars" RAM test appears, after which the ... -
48K Issue 2 Spectrum showing exactly 16KI've acquired an issue 2 and it quickly became clear that only 16K of memory is available. I've read that some early 48K Spectrums with malfunctionin…
... Spectrums with malfunctioning upper RAM were sold as 16K versions. All IC ... slots are populated and the upper RAM ... PEEK 23733*256 returned 32767. 16K games load and 48K games ... the upper RAM has been disabled? If the lowest upper RAM IC ... -
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 …
... board (I've checked, the upper memory is present!). It's ... faulty, or a 16K (it isn't a 16K).
carrying ... issues are only in the upper RAM as it will actually boot ... -
The Complete List Of The Causes Of Lower Ram Failure?Well the aim is to get a comprehensive list.I ask this because I know very little about it . I know that failure of "power supply" related capacitors…
Well the aim is to get a comprehensive list.I ask this because I know very little about it . I know that failure of "power supply" related capacitors can do this . But I suspect there are loads of other ways to damage lower RAM ICs? Any ideas? -
OopsToday is a sad day :confused: Poor old rubber keys has gone t**s up. :( All i get is a black screen with a white border. Any body got any ideas …
... failure of the -5v supply, faulty 4116 RAM (lower 16k), faulty ULA, faulty upper RAM ... -
Born again Speccy user with problemsHello all, Firstly I'd like to say a big hello - this is my first post! When I was 8 or 9 or so my dad bought a ZX Spectrum 48K and a whole bunch o…
... very first byte of upper RAM and sometimes that is ... a normal 16K model if it detects all upper RAM is faulty ... bit 1 of all upper RAM and your test does ... a 4164 or all of upper RAM with one of these: ... The most common cause of failure to load is not supplying ... -
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…
... this down to a RAM failure of some sort.
upper RAM from the system ... CAS signal from the upper memory bank. Mcleod_ideafix ... this, except the "upper" RAM chips are disabled, not ... 16k model.
Why am I being pedantic? Well, sometimes a RAM ... -
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…
... specific a potential broken upper memory chip, by ... RAM is 16K and the ROM is 16K)[/QUOTE]
The simplest failure ... position for all of upper RAM (e.g. IC22 ... the first byte of upper RAM (as you say) ... br />
An upper RAM chip might have failed in ... -
The Different Approaches To Upgrading the ZX Spectrum from 16K to 48K This is probably something that has been covered before . I will take a look to see if I can find anything on WOS
... />
And here the "upper ram module" is introduced:-
16k-spectrum-to-48k/"]https:// ... .com/technical/upgrading-a-16k-spectrum-to-48k/[/url]< ... 16k . I expect customers might be surprised if their 48k machines "failure ... -
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…
... here it looks like an upper memory fault.
Before ... -
Issue 2 headache!Ive got an issue 2 here that firstly had a blown regulator (fixed), now its reading as a 16k machine (its fully populated), ive replaced and socketed…
... 16k machine (its fully populated), ive replaced and socketed the whole upper RAM ... , still same issue, Paul Farrows RAM tester produced ...
