The Inves Spectrum+ (link provided by Zonadepruebas) was a Spectrum 48K clone made by Investronica, the spanish partner of Sinclair Research, and responsible for Sinclair distribution in Spain.

This clone has suffered from numerous incompatibilities, mainly because of its non standard ROM, altered in some ways, mostly of them to comply with spanish regulation, that demanded that every computer with less than 64K had to be "spanished". That is: error messages had to be in spanish, and the keyboard and screen had to be able to display some spanish characters, like Ñ, ¡ and ¿

Among the features of the Inves Spectrum, there was one that we can consider "unique" on the history of Sinclair computers: the Inves Spectrum was presumely the first Spectrum clone that could be damaged permanently by issuing instructions...

The Spectrum internal speaker is not a robust manufactured one. The two tiny wires that come from the inside are directly soldered to the outer pads, that in turn are soldered to the pins that go to the PCB. This means that a rework on this pads may lead to wire brokerage and thus, rendering the speaker useless.

This is a ZX Spectrum 48K, issue 6A, from ZXevious. He asked me for advice on how to repair its speccy. Came with a faulty Interface 1, which I speak about in another article.

Upon switching on, the screen shows flashing blocks, hangs, and the screen data is mixed with something that seems digital noise. Maybe from poorly coupled data lines.

ULA is operational, Z80 too, so the main candidate is low memory. First thing is to try to isolate which memory chip (or chips) are damaged. The usual cartridge ROM tests I ran didn't give a clue, as it seemed that every chip was damaged. Strange enough that all power lines were ok.

This is a issue 3B Spectrum, with no socketed chip except the ULA and one suspicious socket at IC12 (bit 6 of low memory). Does initial boot-up, but it hangs before showing the copyright message.

This sympthon uses to be a failure in low memory. So I plugged my JetPac ROM cartridge and turned on the system. The JetPac ROM version LDIR's a presentation screen from some location at the ROM cartridge, right to the screen memory area. This screen helps me find if there's any low memory bit position that does not work. This is what I saw:

Received on May, 24. The machine does not boot. Flashing blocks. Machine is a issue 3B PCB.

I first did a visual inspection. No aparent damage. Hooked a Sinclair Interface II and tried different ROM's. When I tried Jet Pac, I realized that a reset failure was happening: this game LDIR's a screen from the ROM cartridge. The screen is the same loading screen as in the tape version.

I did a manual reset, shorting C27, and voila! JetPac loaded.