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toasted soeccysHello, ive jsut bought a pair of speccys on ebay (one 16k issue 2 & a prob 48k issue 3) unfortunaly the genius who sold them tried to see if the wor…
... and GND to the 4116 RAM with the +12/-5v supplies ... is likely to fry your lower RAM! Hideous devices, these 4116s...not ... ][LIST]
[*]Power supplies: Ok, lower RAM might fry with my *bright ... way to go. Especially with lower RAM, some video effect might be ... -
TV Modulator. Can it be repaired?Is it possible, to repair tha TV modulator (after removing it) if it gives wavy picture? I replaced both transistors (tr1/2) and both electrolytic ca…
... fix, you just change the lower RAM and it bursts into life ... one you change all the RAM and the CPU turns out ... . Won't take a 32K RAM expansion and everything on that ... -
TV Modulator. Can it be repaired?Is it possible, to repair tha TV modulator (after removing it) if it gives wavy picture? I replaced both transistors (tr1/2) and both electrolytic ca…
... as if there is bad lower RAM or TR3, ZTX313 is ... down. The RAM is working fine, and the ... Research Ltd, but only lower 16K only working. Ramtop ... computer can see all the RAM above 32768 - it just ... in every location in upper RAM - so it's half ... -
TV Modulator. Can it be repaired?Is it possible, to repair tha TV modulator (after removing it) if it gives wavy picture? I replaced both transistors (tr1/2) and both electrolytic ca…
... as if there is bad lower RAM or TR3, ZTX313 is ... Research Ltd, but only lower 16K only working. Ramtop ... lower 16K, so it all points to speed (AKA RAM ... reading does not know, RAM access time is usually ... stamped right after the RAM part number, generally after ... -
Problem with my speccy 48+My machine boots up but apon booting it freezes and you can see feint grey horizontal 1 pixel lines going down the screen. Is this fixable at all?
I think it'll be lower RAM. Those liines you see on ... message if there is enough RAM, but if PRAMT (Physical RAMTop ... the machine stack in screen RAM. Shouldn't be grey though ... -
On a 48K issue 6A......how can i isolate the 32K block? I want to test if there is any fault on the 4116's , leaving the 4532's out of the equation. Will removing the …
Also test the power supply transistors! Do you have the voltages to run the lower RAM?
Test TR3, that'll make the lower RAM appear dodgy if it's gone.
Test IC28 74LS04 too. -
On a 48K issue 6A......how can i isolate the 32K block? I want to test if there is any fault on the 4116's , leaving the 4532's out of the equation. Will removing the …
... garbage that's in lower memory, indicating that lower memory isn't ... the voltages are right on lower RAM, the 4116s are not single ... -
On a 48K issue 6A......how can i isolate the 32K block? I want to test if there is any fault on the 4116's , leaving the 4532's out of the equation. Will removing the …
... the lower RAM?
Test TR3, that'll make the lower RAM appear ... too.[/QUOTE]
The lower ram voltages are fine and i ... power supply.[/QUOTE]
Lower mem voltages:
Pin ... -
On a 48K issue 6A......how can i isolate the 32K block? I want to test if there is any fault on the 4116's , leaving the 4532's out of the equation. Will removing the …
... for each pin of each ram ic to rom, logic, ula ... case something was interfering with lower ram but still... nothing. No broken ... -
Spectrum 48K ROMHi Can anybody help I have an Issue 6a Circuit Board which has a faulty ROM Chip. Is it possible to program a ROM Chip with the 48K ROM and fit it as…
... seems related to
a) RAM refresh
b) ULA bus ... linked to same line in lower RAM.
In R is linked ... is linked directly to the RAM, and RASL in the ULA ... of the schematic do the RAM refresh, but I'm no ... -
Spectrum 48K ROMHi Can anybody help I have an Issue 6a Circuit Board which has a faulty ROM Chip. Is it possible to program a ROM Chip with the 48K ROM and fit it as…
Cheers
I had not spotted that, would it be to enable a wider selection of lower RAM chips used ? -
Problem with my speccy 48+My machine boots up but apon booting it freezes and you can see feint grey horizontal 1 pixel lines going down the screen. Is this fixable at all?
... most likely cause is failed lower RAM. However, since it's easy ... -
non standard loader bar coloursAs with my speedloader thread, when did non standard colours start to appear and who came up with the idea and what was the reaction?
... , intensive writing to the lower 16K RAM may cause timing problems due ... I was assembling it into lower RAM. -
BooHoo....Broken Speccy on 25th anniversary!Speccy broke today (today of all days!!) I'm presented with black screen on power up, anybody any ideas what might have gone wrong and any repair ti…
Almost certainly a bad 4116 lower RAM chip.
Repair means ... -
Reason for strange display layout?I have always wondered if there is any technical reason behind the strange layout of the display file or why did Sinclair choose to do it this way?
... required much more contention for lower RAM with the Spectrum's simple ... the screen picture read the RAM only when the CPU didn ... given that the slowest static RAM today has an access time ... -
48K Speccy not workingHey, A few months ago (hope it´s not to late) I was loading a game into my speccy and from one moment to another it stopped working! I unplugge…
... to check (once again) the lower RAM voltages, because a common component ... have dead lower memory (according to the TMS4116 datasheet, 4116 RAM will ... -
48K Speccy not workingHey, A few months ago (hope it´s not to late) I was loading a game into my speccy and from one moment to another it stopped working! I unplugge…
... /> ULA, Z80, power supply transistors, lower RAM and tr8, tr9 transistors were ... -
Running code from the display memory?Is it possible to run machine code from the memory area used by the display file? If you were really out of memory and some part of screen is not u…
Each 3rd of the screen provides 2Kb of memory (and an additional 256 bytes if you include the attributes area).
Nice one Icabod, it never occurred to me though of the fact that the lower RAM isn't contended during the border trace! -
Unconventional way of diagnosing a faultHi everyone Some time ago I got a 48k Spectrum (issue 3B board) in a pretty bad condition. I believe the power supply transistor TR4 failed, causing…
... the only fault is lower RAM, it's unlikely you ... can think of where lower RAM has failed in such ...
Since the 4116 RAM would have likely been damaged ... desolder all the 4116 RAM and put them in ... be fully functional and lower RAM can be completely goosed.< ... -
Unconventional way of diagnosing a faultHi everyone Some time ago I got a 48k Spectrum (issue 3B board) in a pretty bad condition. I believe the power supply transistor TR4 failed, causing…
... I can think of where lower RAM has failed in such a ... />
[QUOTE]Since the 4116 RAM would have likely been damaged ... would desolder all the 4116 RAM and put them in sockets ... 't be fully functional and lower RAM can be completely goosed.[/QUOTE ... -
UlaI remplaced an ULA 6c001-6 by an ULA 6c001-7 chip on issue 3B board. It is "crucial" to remove R32 and adding the 2x NAND gates ??? or not ? Thanks.
Not really, they get used plenty anyway - whenever lower RAM is accessed (so regularly by the ULA) -
UlaI remplaced an ULA 6c001-6 by an ULA 6c001-7 chip on issue 3B board. It is "crucial" to remove R32 and adding the 2x NAND gates ??? or not ? Thanks.
[QUOTE=Winston;197694]Not really, they get used plenty anyway - whenever lower RAM is accessed (so regularly by the ULA)[/QUOTE]
Humm, maybe changing the R32 value to 150 or 220 Ohms ?
(2x NAND gates do an 20-30 ns propagation delay) -
Disable onboard memoryWould this work...? Access to onboard I/O can be disabled by holding IORQGE high. Would it be possible to create a MEMRQGE in a similar way to disa…
The ULA controls the lower RAM (including contention by withdrawing the ... if the CPU goes for lower RAM at the same time as ... the /CAS signal from reaching lower RAM when you want yours paged ... left alone - and that way, lower RAM will continue to get refreshed ... -
Poorly Spectrum + Fault diagnosis help needed!Hi, I've got a Spectrum+. Sometime in the past I broke it and sent it off to be fixed. It came back working good as new, but with an issue 2 board i…
Almost certainly the lower 4116 RAM. The ULA normally gets ... usually does so because the lower RAM went bad.
RAM. Refer to the diagram ... one of the 4116 RAM chips, and check the ... changing out the 4116 RAM. You'll probably find ... -
Poorly Spectrum + Fault diagnosis help needed!Hi, I've got a Spectrum+. Sometime in the past I broke it and sent it off to be fixed. It came back working good as new, but with an issue 2 board i…
... if any of the 4116 RAM is non-intermittently bad (i ... shots, it's been bad lower RAM. (That's not to say ... 't cause that, but 4116 RAM doesn't seem to age ... would suggest swapping the 4116 RAM for known good 4116 first ... -
Poorly Spectrum + Fault diagnosis help needed!Hi, I've got a Spectrum+. Sometime in the past I broke it and sent it off to be fixed. It came back working good as new, but with an issue 2 board i…
... if any of the 4116 RAM is non-intermittently bad (i ... shots, it's been bad lower RAM. (That's not to say ... 't cause that, but 4116 RAM doesn't seem to age ... would suggest swapping the 4116 RAM for known good 4116 first ... -
Poorly Spectrum + Fault diagnosis help needed!Hi, I've got a Spectrum+. Sometime in the past I broke it and sent it off to be fixed. It came back working good as new, but with an issue 2 board i…
... hot. Especially the 4116 RAM chips. Change any 4116 ... 4) Test upper RAM - sometimes, bad upper RAM just stops working so ... t work. Sometimes, bad RAM will stop the machine initialising ... , and fool you into suspecting lower RAM!
Really, you ... -
Spectrum Diagnosis: Purple is not my colour!Hi, I thought the self-fault-finding amongst you might appreciate my learning experience this afternoon in fixing my home-made speccy 48K. Yesterda…
... changed all 8 of the lower ram chips with another kind of ... just black).
The two lower pins of each chip (right ... had already removed all upper ram chips (and installed bases) untill ... -
Poorly Spectrum + Fault diagnosis help needed!Hi, I've got a Spectrum+. Sometime in the past I broke it and sent it off to be fixed. It came back working good as new, but with an issue 2 board i…
Thanks to the kind RAM chip doner, I got the ... at a speccy with dead lower RAM. :???:
I think this ...
