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Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... work out where physical RAM finishes. It is not a full memory ... "lower" RAM).
A lot of the initialization code does not need ... to use the "upper" RAM. So sometimes ... display before the "upper" RAM fault causes the CPU to ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... work out where physical RAM finishes. It is not a full memory ... "lower" RAM).
A lot of the initialization code does not need ... to use the "upper" RAM. So sometimes ... display before the "upper" RAM fault causes the CPU to ... -
Weird output...Last week I found my old ZX Spectrum 48k and I tried to connect it to my tv... After tuning it (at 583MHz - C35, it's the only one with signal) it s…
... and -5V DC supplies are not being produced. As Balford says ... colour encoder and the 16k "lower" RAM area (which is where the ... -
Poorly Issue One 16k spectrum diagnosis?Hello, everyone. :smile: I was lucky enough to buy an Issue One 16k rubber key the other week; I didn't know it was an Issue One till I opened it up…
... =Trafferth;768946]1. (With 4116 RAM installed): Speccy sends a low ... multiplexer output is low are not quite high enough. If this ... ICs you're using are not all in good order or ... supplies, though the symptoms are not typical of a lower RAM fault. -
Spectrum Plus display issueHi, does anyone know if this is fixable at all by someone with no experience? From looking on a similar post on World of Spectrum forum they mention…
Faulty lower RAM could be preventing the CPU ... always caused by faulty upper RAM. It seems that a failed ... its output when it's not supposed to.
I ... -
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…
... the first byte of upper RAM (01010101 and 10101010 respectively). If ... with reasonable confidence which upper RAM chip(s) have failed.
One thing is not completely clear, but it might ... the extended memory, as the lower RAM is 16K and the ROM ... -
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…
... ]
One thing is not completely clear, but it might ... extended memory, as the lower RAM is 16K and the ROM ... position for all of upper RAM (e.g. IC22 stores ... the first byte of upper RAM (as you say) will ... .
An upper RAM chip might have failed in ... -
Simple Question! RAM InterfaceI was messing around on my spectrum yesterday and blew it up! Im sure it has to do with the RAM joystick interface I bought but hadn't tested. Is the…
... more of the lower RAM ICs to fail. It should not be powered ... able to verify whether or not TR4 (and/or TR5, which ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... little more Zorn sells replacement lower RAM boards which replace all 8 ... and made sure PIN8 was not touching the PCB (measured) I ... -
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…
... just a small area of lower RAM. It stripes a random sequence ... most of the common Spectrum RAM faults.[/QUOTE]From this site ... -1.tzx[/URL]
{Not my code by the way ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... try removing all the upper RAM, and reintroducing it one IC ... /> If not, you could try the same troubleshooting methods as with lower RAM ... -
Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... try removing all the upper RAM, and reintroducing it one IC ... /> If not, you could try the same troubleshooting methods as with lower RAM ... />
B[/QUOTE]
Not on sockets, yet.
lower memory soon.
Guess I ... -
ZX Spectrum 48K AV IssueOK so I dugout my old 48K Speccy today and decided to AV mod it. I did the mod (pretty easy) but the picture I am getting is this. [url=http://posti…
... /> - There's a failure in lower RAM or one of the supply ... measurements, and be extremely careful not to short adjacent pins when ... -
ZX Spectrum 48K AV IssueOK so I dugout my old 48K Speccy today and decided to AV mod it. I did the mod (pretty easy) but the picture I am getting is this. [url=http://posti…
... A7 is not floating (and limiting the the ram to 32K ... Pin16= GND
4164: Pin1 = Not conn, Pin8 = +5V, Pin9= A7 ... is connected to the "Not connected" pin of the ... The +12V is not connected to the ram at all, as ... less likely to fry the lower ram if TR4/TR5 blow ... -
ZX Spectrum 48K Issue 3, loss of -5V rail.Hi all, I've googled this problem and poured over the electrical diagrams for the circuitry concerning the power supplies and I believe I know what …
... voltages. If it's still not got -5V, and the electrolytics ... s the coil or a RAM chip. Change the coil ... have to work through the lower RAM.
It's [ ... vertical bar which denotes a RAM chip holding the line ... high or low. The RAM chips with no -5V ... -
Powering a Spectrum with 5v?I live in the States, but I'm originally from England. My original Spectrum is still at my mum's house in the UK, and I was thinking of asking her t…
... V supply, but it might not be so simple as bypassing ... . It's not something I have tried. The lower RAM ICs require -5 ... -
Help put this back to 16kSo this issue 2 arrived today and ive opened it up just to nosey and confirm that infact it is an issue 2. Now from the help offered in an earlier po…
... :x ,i think the whole lower ram are gone as they all ... :its looking like a modern lower ram module maybe 2 transisters and ... was fully expecting it to not work as i said it ... -
Help put this back to 16kSo this issue 2 arrived today and ive opened it up just to nosey and confirm that infact it is an issue 2. Now from the help offered in an earlier po…
... the chances of damaging the lower RAM. However, if you've ... at the lower RAM.
- If the voltages are not correct ... given your description of overheating lower RAM ICs, I'd probably ... lower RAM module and hopefully it'll work at this point. If not ... -
ZX Spectrum 48K Issue 3, loss of -5V rail.Hi all, I've googled this problem and poured over the electrical diagrams for the circuitry concerning the power supplies and I believe I know what …
... matter if you use the lower RAM replacement module, but it'd ... find out why it's not right. -
Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... and 12V to run the lower RAM - this means the voltage ... going to remove all the lower RAM chips anyway, so personally ... to make sure you've not left any solder splashes ... , that's POINT ONE - not one) of a volt. At ... now, fit Zorn's lower RAM board and see if it ... -
Next step for fixing my speccy?Hi guys, I've picked up my faulty Spectrum aiming to fix it. So I followed the excellent JouledperCoulomb videos on Youtube for the basics and I am …
... and 12V to run the lower RAM - this means the ... to remove all the lower RAM chips anyway, so personally ... make sure you've not left any solder splashes ... that's POINT ONE - not one) of a volt. At ...
I'll remove the lower ram, check the voltages, fit sockets ... -
RAM issue for potential 48k buy?Hi guys I've got a 48k in my sight for ?20 but... it has an issue: [QUOTE]"I tested the computer and only displayed a distorted screen. Coloured …
... [/IMG]
I'm not too familiar with the ZX ... /IMG_20140824_204148.jpg[/IMG]
Not sure if its worth salvaging ... for my 48k if the lower RAM ever went wrong on that ... cheap enough anyway...
not sure... :-? -
Short Circuit Damage?Hey Spectrum fans, Currently trying to diagnose what is wrong with my 48K Issue 4B ZX Spectrum. The initial problem was the fact it would not boot -…
... to run the lower RAM chips. Pull all 4116 RAM chips from their ... TR4 is probably ok - if not, that's where you start ... buy one of those little lower RAM boards that Zorn sells and ... -
Spectrum 48k ProblemsHi all Got my 48k today but it's playing up abit... First time i turn it on it was like this: [IMG]http://s26.postimg.org/hlg9d3f3d/IMG_20140830_…
... one (or more) of the "lower" RAM chips (type number 4116).
not working correctly and is failing ... -5V supply that the 4116 RAM chips need. If this -5V ... supply is missing, the 4116 RAM chips May self destruct.
48K Ram Check Command not workingI am trying to repair my Spectrum 48k. It is having issues loading games, sometimes they load all the way to launch and then the speccy resets. Oth…
... only seeing 16k of Ram and that my fault lies in the lower ram?48K Ram Check Command not workingI am trying to repair my Spectrum 48k. It is having issues loading games, sometimes they load all the way to launch and then the speccy resets. Oth…
... only seeing 16k of Ram and that my fault lies in the lower ram ... ?[/QUOTE]
As Zorn said, fault is in upper ram ...48K Ram Check Command not workingI am trying to repair my Spectrum 48k. It is having issues loading games, sometimes they load all the way to launch and then the speccy resets. Oth…
... the system is seeing only 16k bytes of RAM. Remember the ... ROM. Next is the "lower" RAM. Then from 32768 to 65 ... the 32k bytes of "upper" RAM.
The type ... known a 1 bit dynamic RAM (DRAM). Each chip provides ... the "upper" 32k of RAM in your machine has ...48k - Why Won't it Buzzzz?Hi WOS ;) I bought a load of Spectrum games off eBay and thrown in for good measure was a 48k 1984 Issue 6a circuit board that I was told was for sp…
So could a faulty lower RAM IC be holding the voltage low across the 12v rail. If not how do I test for a short between the RAM IC's and the 12v rail?Harlequin clone...PCB manufactured!Using Chris Smith's detailed schematics and project notes from the Harlequin... a Speccy fan in the United States by the name of Don (Superfo) has de…
... that did not work right in the position of U8 (lower RAM = video ... it will also work if RAM change will be neccessary in ... the RAMs that actually did not work:
[IMG]http://www ...Spectrum sometimes boots with graphic issuesA while ago, my Spectrum 48K (issue 3B) broke down after fiddling with a brand new joystick interface in combination with DivIDE. Today I tested the …
... to affect a whole byte, not a single bit. You might ... the CPU address to the lower RAM chips.
One of ...
