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ZX Spectrum+ showing 16K of RAMHello again, as the title says my ZX Spectrum+ is showing only 16K of RAM instead of 48K when running a memory check. [url="http://www.1000bit.it/su…
... IC13 is part of the lower RAM and the Spectrum is showing ... the first 16K of RAM working fine.
I'll ... I'll have the new RAM to make sure it works ... -
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…
What kind of lower RAM chips have you installed? They should have 150ns access time (4116-2N type). 4116-3 are slower and their access time is 200ns.
Are you sure that Z80 CPU is fine? -
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 ... and write to the 4116 "lower" RAM. So when it detects a ... -
Spectrum repairs[edit - sorry! wrong section, if someone can move please] I'm in contact with a seller on Gumtree. He was selling a 48k Spectrum, fully boxed and…
... is a fault with the lower RAM (could be just a single ... could also be that the RAM fault took out the DC ... turn killed more of the RAM. Or the Z80 CPU could ... -
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…
I'm sorted for the lower ram just need the upper ram IC.
Is there any drop-in replacements for the TMS 4532-15NL4? Would a Samsung 4164-150NS work? -
Memory Contention: A Hypothetical Fix?I have just had this crazy thought: If one were to wire an additional memory chip, say a 6264 8Kx8 SRAM, in parallel with the main memory so that it …
... bus isolation between the lower 16k RAM and the Z80 ... trying to access the lower 16k even though it ... or reading to the lower 16k of RAM.
... from the lower RAM to some new "screen" RAM during the ... only reads from this new RAM.
This ... -
Replacing lower RAM 4116 ZX Spectrum 48k - desoldering advice please?A long post, but interesting pictures perhaps. :) I'd like some advice: (also apologies I think I picked the wrong 'Hardware' category for this, plea…
... . Yes there maybe some faulty lower ram IC's, but don't ... rule out any faulty upper ram IC's either.[/quote]
lower ram ICs were broken. I only ... -
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…
... The 4116 (or equivalent) "lower" DRAM chips NEED a +12V ...
[quote="RSwipeCA;55309"]My lower RAM voltages are -5V = -029.5mV ... chips (all the 4116 "lower" RAM chips and I recommend removing ... the 4116 (or equivalent) "lower" RAM chips back in. Then power ... -
What's going on inside this ZX Spectrum? [Newbie]Hello folks Last year I got hold of a ZX Spectrum. At the time it appeared to boot up fine, but more recently when I've tried to boot up I've had…
... . One or more faulty upper RAM ICs interfering on the data ... />
4. Faulty lower RAM. The most common lower RAM faults don't cause ... and can lead to the lower RAM being damaged. Be aware that ... -
Replacing lower RAM 4116 ZX Spectrum 48k - desoldering advice please?A long post, but interesting pictures perhaps. :) I'd like some advice: (also apologies I think I picked the wrong 'Hardware' category for this, plea…
... be worthwhile disabling the "upper" RAM, then retesting (ask for help ... /> Then, maybe resume replacing the lower RAM. But in order to save ... -
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…
... .
I desoldered all the RAM chips and socketed them. I ... got these voltages at the lower RAM sockets -5v = -4.84v, 12v ... -
problem loading/playing gameshello to all! i was last active at this forum 11 years ago, and here goes the same thing :) found my old speccy, did the composite mod, managed to …
... are the one for upper ram?
i am attaching an ... now... it seems like the lower ram is gone but the upper ... -
problem loading/playing gameshello to all! i was last active at this forum 11 years ago, and here goes the same thing :) found my old speccy, did the composite mod, managed to …
No, the lower RAM is there. It’s the eight ICs in the lower left corner. The upper RAM and at least three other logic ICs—a multiplexor, a NAND gate, and an OR gate are missing, however.
Did you have a gremlin as a pet at some point? -
problem loading/playing gameshello to all! i was last active at this forum 11 years ago, and here goes the same thing :) found my old speccy, did the composite mod, managed to …
[quote="Ast_A_Moore;927726"]No, the lower RAM is there. It’s the ... ICs in the lower left corner. The upper RAM and at least ... -
Replacing lower RAM 4116 ZX Spectrum 48k - desoldering advice please?A long post, but interesting pictures perhaps. :) I'd like some advice: (also apologies I think I picked the wrong 'Hardware' category for this, plea…
... fiddling and pressing in the lower ram ICs that's ive flexed ... to see if the upper ram was preventing it from starting ... -
Broken Issue 2 - likely culpritsI've just got hold of an issue 2 spectrum with an interesting layout (heatsink is vertical and goes down to the speaker, some variable resistors and …
... the 5V rail of the lower ram chips. It shouldn’t go ... the 12V rail of the lower ram chips. It should be somewhere ... -
Broken Issue 2 - likely culpritsI've just got hold of an issue 2 spectrum with an interesting layout (heatsink is vertical and goes down to the speaker, some variable resistors and …
... z80, ROM and all the lower RAM ICs (even though I couldn ... machine is hanging on the RAM test routine I'm thinking ... is to start pulling the lower RAM ICs until I find a ... -
Broken Issue 2 - likely culpritsI've just got hold of an issue 2 spectrum with an interesting layout (heatsink is vertical and goes down to the speaker, some variable resistors and …
Hmm, replaced all the lower RAM ICs with new chips but ... -
Broken Issue 2 - likely culpritsI've just got hold of an issue 2 spectrum with an interesting layout (heatsink is vertical and goes down to the speaker, some variable resistors and …
Yes, if the /RAS signal from the ULA to the 'lower' RAM chips is poor, it will cause problems. But it is worthwhile checking the 'faulty' ULA in a known good machine.
[b][i]Mark[/i][/b] -
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…
Have you removed and reseated the ULA? Also, one of the lower RAM ICs has already been swapped with a different type than the others, this could be causing instability of the type seen in your screenshot.
Bryce. -
Spectrum stuff online "buying skills". Are real skills needed for low cost Speccy items? Firstly , there are some pretty fundamental requirements that are probably too basic to mention , like buying the right software at the right pri…
... /filter capacitors to a few RAM ICs (possibly a few other ... need one; likely just the lower RAM ICs. Smaller capacitances installed in ... -
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 …
... more of either upper or lower ram IC's have failed due ... , when TR4/TR5 failed. Upper/lower ram IC's need -12v,+12v ... -
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 …
... more of either upper or lower ram IC's have failed due ... , when TR4/TR5 failed. Upper/lower ram IC's need -12v,+12v ... -
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 …
... the -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 quickest ... way of fault finding suspect RAM problems, is to run a ... -
Fixing a poorly Issue 3 - Odd faults.Here's one for you Spectrum fixers, I warn you it's a long one. I've spent a couple hours this evening doing several repairs on a rubber keyed Speccy…
... and the machine passed lower and upper ram tests. Switched on without ... have a spare one those lower ram modules, I may replace all ... the ram with it and give that ... -
Fixing a poorly Issue 3 - Odd faults.Here's one for you Spectrum fixers, I warn you it's a long one. I've spent a couple hours this evening doing several repairs on a rubber keyed Speccy…
... removed all the old lower ram ic's and fitted ... shorts. Fitted a spare lower ram module and was greeted ... graphics garbage with no ram present. I also checked ... continuity between the ram module pins, and solder ... have to buy more lower ram ic's, or another ... -
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 …
I'd suspect the lower RAM chips first - obviously check ... corrupted - indicative of faulty RAM, and I'd say an ... messed up by a faulty RAM chip or two. Not ... you can still get a lower RAM board, but that may ... good way forward if indeed lower RAM is to blame, those ... -
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…
...
Remapping memory, be it RAM or ROM is relatively simple ... ULA controls the ROM and lower RAM area, but 74 series ... control the upper 32k of RAM. The board design is ... out the ROM and put RAM in it’s place, ... ZX Spectrum with 80k of RAM and a built in ... -
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 …
... value on screen. If the RAM was working correctly, you should ... /> If BASIC works, then the lower RAM is fine.
The ... tests from the highest possible RAM address down to the lowest ... possible RAM address.
[b][i ... -
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…
... white screen? I know sometimes ram chips can be faulty, or ... if the Spectrum has faulty ram IC's. The diagnostic rom ... fault with 1 or more lower ram IC's. But the other ...
