Sinclair ZX80 / ZX81 / Z88 Forums

Internal mounting attempt for 1500/Spectrum envelope.

Only video port (RF RCA) thru-hole created (botched) for 1500. The damn TI99 has vent holes at top rear of case so spines broke. Every Sinclair user knows that is not where they go... they go on the bottom next to the table it is sitting on!

Keyboard not modified and keyboard PCB not installed.

Thanks for all the help i was able to work it out and have the keyboard working on my spectrum .

Now i have a 128k spectrum board that i love to get it in a ti99 case have another ti that is non working for the transplant.
This keyboard is much more nice to type that the previous one also and this ti looks to be like new.

The only problem is the keyboard looks quite different than the previous one.
Any idea of how i can modify it ?.

Glad to hear! I have the Alps keyboard as well. Just follow the yellow brick road. Pinout is the same. Maybe I'll have the kit ready in time for you.

Charles

You are going to do a conversion kit ?, how it works ?, will wait for it .

The keyboard conversion kit is tentatively for Spec 48 and TS1500 internal mounting. Is the 128 the same PCB board layout? Size and keyboard locations?

The ZX Spectrum 128k "toastrack" uses the same keyboard as the ZX Spectrum+

And the ZX Spectrum+ keyboard works with any 16k or 48k PCB (but may require a resistor to be changed).

However, the ZX Spectrum 128k "toastrack" PCB is a different shape due to the extra connectors, so it would not fit in the case of an earlier machine without some case or PCB hacking...

Mark

Maybe someone can send me photocopies of the backside of the +, 128, +2,+3 (have I forgotten any?) with a hard measurement of some mounting holes in the X AND Y directions (to check for incongruent aspect ratio) so I can evaluate layout whether I can include them.

Photocopying the back allows a relatively flat layout of the solder side without perspective changing aspect or pincushion from cameras. Fairly perpendicular picture of component layout allow me to understand device locations.

The complete range of ZX Spectrum models is:-

• ZX Spectrum 16k "rubber key".
• ZX Spectrum 48k "rubber key".
• ZX Spectrum+ (note that machines sold by Sinclair were 48k, but as Sinclair also sold a keyboard upgrade, it's possible for 16k versions to exist, either because a 16k rubber key was upgraded, or due to a failure of one or more of the 32k DRAM chips).
• ZX Spectrum 128k "toastrack"
• ZX Spectrum +2 (in a dark grey case, uses a 9V power supply unit and connects to the computer with a 2.1mm/5.5mm 'barrel' plug)
• ZX Spectrum +2A (in a black case, uses a PSU that has multiple outputs, with a DIN plug, note that most +2A units actually have the later +2B PCB)
• ZX Spectrum +2B (Like the +2A, Amstrad corrected a design error that affected the audio circuits)
• ZX Spectrum +3
• ZX Spectrum +3B (Like the +3, Amstrad corrected a design error that affected the audio circuits)

The PCB used in the first +2A and all the +3 machines is the same board, just fitted with different components (tape or disk system). It suffered from poor audio from the AY sound chip.

Mark

Now the issue 2 onwards PCBs for the 16k and 48k machines are all the same size. They will fit in the rubber key cases or the plus cases.
The 128k only fits in it's own case.
The +2A and +2B cases are the same apart from the moulded text on the bottom. The case is very similar to the +2 (grey).
The +3 and the +3B cases are the same.

The plus and the 128k use a double layer membrane, so when an extra key is pressed, two different membrane contact switches make.

The +2 (grey) also uses the same technique, but uses a different membrane. This has both tails at one end (and at right angles to the earlier keyboard membranes).

The +2A, +2B, +3 and +3B all use the same keyboard. Note that this keyboard membrane is different from all the earlier membranes, as it is a single layer with the extra keys wired differently (the Amstrad gate array does the encoding for the extra keys).

Mark

That is a lot of work it could be simpler that the adapter just have some pins for each zx keyboard signal and then you can do your own wiring at your own need.

I i have a couple of zx spectrum russian clones in need of a good home, and borked ti99s are not that rare and quite cheap they do ideal cases.

Purchased it on sellmyretro as a kit and build it in a couple of days but now i'm stuck and in need of a keyboard for it