Sinclair ZX80 / ZX81 / Z88 Forums

I have tried everything (settings, apps, but without audio amplifier) on three different Samsung smartphones and it's not loud enough. I think Samsung is too concerned about its customers...

The composite image is not perfect - there are "ghost letters" around the actual letters. Is this normal or can it be improved? I assume you are using a LCD TV? This is typical on some LCD TVs. Look in the user controls menu/settings, see if there are any noise reduction or picture enhancement sett...

First I would like to report on the power supply upgrade, which was a mixed success. I had no trouble removing the old diodes and capacitor, but I had a big problem removing the transformer as it was soldered by two HUGE blobs. The copper traces there have retracted from the board; I have already or...

After playing a bit with my ZX Spectrum, I noticed some problems. The computer is unstable. After a while it freezes or resets. At first the problems were very consistent, with thick purple vertical lines, so I stopped them by replacing the bit 0 lower memory DRAM memory. Now the problems occur much...

Be careful with the cheap step-down circuits, some are not particularly reliable apparently. I’m only going on what some other people have said though. Of course, I will test it on high currents first before using it for ZX Spectrum. And I think the risks are relatively low, aren't they? The step-d...

If this "thing" is not original, then I am definitely interested in replacing it with a diode or two. I also bought a couple of TSR1-2450s from AliExpress and am impressed with how well they work and how cold they are at 0.5A. However, I have not decided if I will actually employ them yet. I want to...

IMG_7132.jpeg What’s the thing that I’ve arrowed? The cable should go from the PCB out through the case via the grommet. Mark I do not know. I thought it was an ancient fuse, but since its resistance is 1.5Ω, it could be a high power resistor reducing the voltage on the ZX Spectrum. Even with this ...

I do not like that the output voltage of the power supply is unbalanced. Would it be a good idea to replace all four diodes and if so, which diodes should I use? I’m not sure what you are asking. The mains power supply unit is an unregulated type made up of a thermal fuse (which may be part of the ...

I have now taken a closer look at the board and compared it with the official circuit diagram. I discovered this mod connected to the extra stereo audio socket (one pin of the socket is unused), which seems to be a bit nonstandard mod for composite video: zx.png 20231024_193117.jpg (IP and 5V are al...

Thank you for your help and patience. I would like to ask you a few more questions Is it normal that the ZX Spectrum only sends picture and no sound via the antenna cable? I do not like that the output voltage of the power supply is unbalanced. Would it be a good idea to replace all four diodes and ...