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Replacing ZTX650 with BD139Today I blew up one of the GALs on one of my DivIDEs while testing on my Toastrack. Shorted M1 with 12V and the 12V circuit broke. I had to replace T…
... only work if the lower RAM is replaced with RAM that does not ... -
Replacing ZTX650 with BD139Today I blew up one of the GALs on one of my DivIDEs while testing on my Toastrack. Shorted M1 with 12V and the 12V circuit broke. I had to replace T…
... the 4116 memory modules for lower ram. Which is why I now ... -
Diagnosing a strange software fault in a 48kHi, A friend gave me a 48k, which I am very keen to restore. The spectrum 48k was my first computer over 20 years ago and I owe my ability to code t…
... the power supply to the lower RAM and cause some/all of ... -
Diagnosing a strange software fault in a 48kHi, A friend gave me a 48k, which I am very keen to restore. The spectrum 48k was my first computer over 20 years ago and I owe my ability to code t…
... is on 4116 RAM IC's in lower left corner of ... amp; shows image (which needs lower RAM + video encoder to work), ... -5V missing can kill lower 16K chips in short order ... various tests to make sure lower 16K works 100% ( ... in place of the upper RAM.
Watch ... -
Semi-Dead Spectrum - Help RequestedI have finally got my hands on my two old Spectrums - neither of which work, but ideally I hope to get both of them working again. Spectrum number o…
Definitely replace all the electrolytic capacitors. A fault in some of them could destroy the lower RAM 4116 ICs and that'd probably be worse than the problem you've got now. -
Diagnosing a strange software fault in a 48kHi, A friend gave me a 48k, which I am very keen to restore. The spectrum 48k was my first computer over 20 years ago and I owe my ability to code t…
... just a small area of lower RAM. It stripes a random sequence ... most of the common Spectrum RAM faults. -
Diagnosing a strange software fault in a 48kHi, A friend gave me a 48k, which I am very keen to restore. The spectrum 48k was my first computer over 20 years ago and I owe my ability to code t…
... /> IC6 is part of the lower RAM and we have no reason ... -
Z80 new old stockHi. I found this on eBay but ... is there a way we could know they don't hav a faulty M1 line? [url]http://www.ebay.com/itm/Zilog-Z80-CPU-Z0840004PS…
... Z80's outputs have much lower output impedance than the older ... overpower the outputs of the lower RAM while the ULA is reading ... memory instead of what the lower RAM is outputting. -
48k faultyHi guys! I have a 48k that, currently, presents 2 problems: 1 - Can?t sync to TV correctly. I get a lot of noise and the characters appear to be inc…
... , +12 and -5V) at the lower RAM.
Only when that ... -
WIP: ULAPlus hardware implementationThis aims to be an "almost" plug-in replacement for the Sinclair ULA chip fitted in Spectrum 16K/48K/Plus machines. It comes in a form of a small PC…
... font), and only uses the lower RAM to display the game. I ... not advisable to put a lower value due to excesive current ... -
My 48K Speccy has died.Hi fellow WoSer's! Wondering if you could help me with my rubber key 48k Spectrum, which died on me this afternoon. It is one I prevoiusly fixed up j…
It is most likely the lower 16K of RAM that has failed. Having ... the supply voltage to the lower RAM, make sure all voltages are ... from radiated heat, but the RAM should not.
Removing ... you confirm it's bad RAM, remove all the chips, put ... -
16k --> 48kI bought a zx and found out it was a 16k since when I execute PRINT PEEK 23733 I get 127 Does it mean I get a lesser model? What limitations do I h…
... the worst case, destroy the lower RAM ICs. -
SPECTRA New from Paul FarrowLooks good! Read about it [URL="http://www.fruitcake.plus.com/Sinclair/Spectrum/Spectra/SpectraInterface.htm"]here[/URL]
... mirroring the Spectrum's lower (read "video") RAM. Depending on the mode ... offer any other rom area ram modes please [/QUOTE]
... bank shadows the Spectrum's lower RAM and separately, you choose which ... the ula contention and video ram to 6k per processor?[/ ... -
Successfully updated Issue 2 48k to 128k?Thanks to the donation by PMSR and through the very patient teachings of Velesoft, I have updated the Issue 2 to work with 128k. However. I have yet …
... . However when measuring A7 on lower ram the signal is remaining on ... wave signal like on higher ram A7.
Perhaps this ... -
Difference between brands of 4164 chips?I have gotten my hands on a batch of several brands of 4164 chips. Examples are NEC D4164C-3 and Mitsubishi M5K4164ANP-15. Anyone knows if any type …
... use these as a 4116 (lower RAM) substitute.
They seem fine ... -
Fully-addressed devices initiative (FADI)I would like to introduce an initiative for those who create new pieces of hardware containing legacy devices with well-known addresses. It says that…
yup, my point was that you only have to look at a 48k funny and the lower ram chips all die ;)
On the other hand you can unplug things from the +3 all day and it doesn't seem to care. -
Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... -5V and 12V for the lower RAM (and 12V for part of ... of a problem with the lower RAM. It's possible you've ... got one or more RAM ICs that are failing only ... -
Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... fault in the upper RAM, not the lower. This is certainly possible ... 're able to, try the RAM test program I created and ... it against the upper and lower RAM and leave it running for ... -
Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... contacts.[/QUOTE]
The upper RAM is soldered to the board ... if it successfully checks the lower RAM?
Will definitely be ... to swapping out the faulty RAM. -
Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... if it successfully checks the lower RAM?[/QUOTE]
It's ... test doesn't identify upper RAM as faulty and then the ... help either if the upper RAM interferes on the data bus ... and 7 in the upper RAM and I believe those are ... -
Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... /> I think replacing the faulty RAM will solve the problem.
The RAM chips are responsible for dealing ... address bus to the RAM, two for the lower RAM and another two ... as that could kill the lower RAM. I want to encourage everyone ... -
Composite video for 48k Capacitor orientationHello, My multisystem TV is acting up and I'm unable to navigate the menu to tune in the RF signal for my speccys. However the A/V input still works.…
... have something to do with lower ram. But I can find nothing ... -
Faulty 48K Issue 3 motherboardHi I have a faulty Issue 3 motherboard and would appreciate it if somebody can steer me in the right direction of where to begin with the fault find…
... /> how did you check the RAM ic's ULA, CPU and ... flashing, etc. as with a lower RAM failure.
I tested ... the RAM IC's, ULA, CPU and ... -
Faulty 48K Issue 3 motherboardHi I have a faulty Issue 3 motherboard and would appreciate it if somebody can steer me in the right direction of where to begin with the fault find…
... screen. I removed the upper RAM and interface chips so that ... again:
- Quit upper ram
- Power on.
- Check ... . Check +5v, +12v, -5v in lower ram.
- If spectrum doesn't ... -
48k fuzzy screen errorHi all, I just got a ZX Spectrum 48k (rubber keys) from eBay and when I plug it in the main screen on the TV is all fuzzy and garbled in the middle.…
... like what happens when the lower RAM is completely broken or missing ... of failure with the 4116 RAM ICs. Fortunately, it's probably ... -
48k + Spectrum Issue 4S Display IssueHi all! Brand new user here. Growing up I had a zx spectrum for a little bit, and recently I have bought a working 48k + Spectrum (Issue 4). I was…
... 't use capacitors with a lower voltage rating than the originals ... you may not with the lower RAM removed)?
I can ... -
48k fuzzy screen errorHi all, I just got a ZX Spectrum 48k (rubber keys) from eBay and when I plug it in the main screen on the TV is all fuzzy and garbled in the middle.…
... the necessary voltages at the lower RAM ICs (as I mention towards ... risk killing any of the RAM ICs that may still be ... -
Issue 4S AnnoyanceRecently ive been going through a few interfaces testing them and I stupidly inserted a "key-less" interface (didnt know at the time but should have …
if all the voltages are present on the lower RAM then I don't see how TR5 can be blown :confused: -
48k + Spectrum Issue 4S Display IssueHi all! Brand new user here. Growing up I had a zx spectrum for a little bit, and recently I have bought a working 48k + Spectrum (Issue 4). I was…
... 7 address lines of the lower RAM. (Similar to what you did ... ULA.
Note that the lower RAM is directly connected to ULA ... resistors to Z80 + ROM + higher RAM. -
Issue 4S AnnoyanceRecently ive been going through a few interfaces testing them and I stupidly inserted a "key-less" interface (didnt know at the time but should have …
Afraid I dont have an oscilloscope Zorn (wouldnt know how to use one anyways!) BUT, I checked the lower RAM wrongly, these are the readings on all lower 16k
Pin 1 0.12v
Pin 8 0.15v
Pin 9 5v
