By disconnecting the output of C126 and reattaching it to the emitter of TR11 (via R130), the audio signal will be removed from the dedicated video outputs, but will still be available on RF – this leads to a very significant quality improvement.
Specifically, the audio signal is not only attached to the RF output, it’s attached much earlier in the video chain – this leads to video distortion on the composite and RGB video outputs. The ZX Spectrum 128k+ (and upon extension the 128k+2, which was a hasty Amstrad clone of the 128k+) suffer from various design flaws which affect their video quality. #4: Fix the video output issues associated with the factory ZX Spectrum 128k+ These modifications require the removal of the PCB, held in by a few screws.
#Sinclair zx spectrum 48k for sale install
As such, on Spectrum restorations I always install a new DC power jack and new EAR / MIC 3.5mm mono connectors, and carefully clean both sides of the edge connector with a white eraser. I/O ports and edge connectors on computers tend to see a lot of use, meaning they get loose, and they can also corrode in storage. #3: Replace power connector and tape connectors The regulator is attached to the heatsink via a bolt – it is important to apply new thermal paste between the new regulator and the heatsink, to ensure that heat is transferred between them efficiently. This is a relatively simple task, as the voltage regulator in the 128k+ is attached to the mainboard via a cable with a push-fit connector. It is therefore recommended to replace it with a 78S05 voltage regulator, which is is rated at 2A and will therefore run cooler and more reliably. The ZX Spectrum 128k+ comes from the factory fitted with a 7805 voltage regulator, rated at a 1A peak output – the computer draws closes to 1A, so running it with peripherals can push the 7805 to its limits. #2: Replace 7805 voltage regulator with an uprated version The new membrane can then be installed – I won’t cover this procedure in detail, as it is already documented comprehensively online. The keyboard membrane itself can then be accessed by removing all the screws on the keyboard backplate, and undoing the screws on the two tail clamps.īrand new keyboard membranes are available to purchase from various retailers – take care to buy the correct type, as the early 16/48k “rubber-key” uses a different membrane from the 48k+/128k+. Inside of the computer before restoration. I always replace these as a matter of course, no matter their condition.Īccessing the keyboard membrane requires dismantling the computer – the ZX Spectrum 128k+ is relatively simple to pull apart, with eight screws on the underside of the case, and two keyboard membrane tails plugged into the mainboard. The ZX Spectrum 128k+, like the 48k and 48k+ before it, uses a membrane keyboard which tends to become brittle with age, and either becomes unreliable or stops working altogether. #6: Replace all the electrolytic capacitors on the mainboard. #5: Fix the audio balancing issues associated with the factory ZX Spectrum 128k+.
#4: Fix the video output issues associated with the factory ZX Spectrum 128k+. #3: Replace power connector and tape connectors. #2: Replace 7805 voltage regulator with an uprated version. Initial testing – computer boots normally, with noticeable “jailbars” on RGB video.Īs the machine seemed to be working okay, I planned out the servicing, preventative maintenance, and upgrades that I wanted to perform, as follows: The computer was in very good condition, and appeared to completely original.Īfter checking that the output voltage on the PSU was as expected, a quick power-on test plugged into the RGB port revealed that the computer seemed to boot up fine.
#Sinclair zx spectrum 48k for sale upgrade
The ZX Spectrum 128k+ was the last Spectrum produced by Sinclair before their takeover by Amstrad, and was affectionately known as the “toastrack” due to the large voltage regulator heatsink on its side – it was an upgrade to the ZX Spectrum 48k+, featuring 128KB RAM, 32KB ROM, an RGB video output, three-channel audio via a AY-3-8912 chip, MIDI compatibility, an RS-232 serial port, and an external keypad. Eventually, a machine in good, boxed, but untested condition with peripherals popped up on Facebook Marketplace – after an hours’ drive up to Newcastle, I put my bartering cap on and managed to get it for a reasonable price. I’ve owned several different Sinclair ZX Spectrum computers over the past couple of years, but I hadn’t got my hands on a 128k+ at this point, so I set about looking to get one for my collection.
0 kommentar(er)
