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ZX Spectrum Test PCB I recently read about one of these (I think it may have been the Retroleum site but I am not sure) and I thought "What a great idea" . As pictured …
... readings
Lower ram IC: a comparision with ... ( -5 volt)
lower left 2.64 ( 12v) .
lower RAM IC. So it appears ... -
ZX Spectrum Test PCB I recently read about one of these (I think it may have been the Retroleum site but I am not sure) and I thought "What a great idea" . As pictured …
Hi Mark
Thanks for that . The readings from the edge connector were consistent with those from the lower RAM -
ROM emulation in softwareHi, first of all -- I only have shallow / uni knowledge of hardware, electronics, and physics. So forgive me for asking things that are out of that …
... to the "lower" 16k RAM area (which contains the display RAM), the ULA ... and refreshing this area of RAM.
If the ... down loader program into the "lower" RAM, then once the new "ROM ... . The Sinclair ROM clears all RAM anyway...
[b][i ... -
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…
... has 1 or more faulty lower 16k ram IC's. They may ... . You can buy a replacement lower ram module these days. One is ... -
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? -
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've brought a replacement lower ram IC from Mutant Caterpillar, and ... for drop-in replacement upper ram IC.
Hopefully I ... -
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…
... replaced them all with a lower ram replacement board:-
... Yes there maybe some faulty lower ram IC's, but don' ... rule out any faulty upper ram IC's either. I ... IC6, which is a lower ram IC, and IC17 which ... is a upper ram IC. This has made ... -
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 ... -
48k packed up after cap changeHi all, I'm relatively new to the Sinclair world, my 8-bit repairs in past was lurking in the dark sides of Acorn, Amstrad and Commodore! I've got…
... mostly functional (it reads screen RAM and creates the video signal ... board are all in the lower RAM area, which had been replaced ... noted that a failing upper RAM IC can interfere with the ... -
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. -
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 ...
