Here are some useful documents I have found or written which I hope will be useful.

EPROM Table

One of the other things I am involved in is graphics. I have had this table knocking about on my hard drive for a while:

It’s available from several sources and I find it very useful. Search as I might, I can’t find out who the original author was. In any case, I have re-drawn it and you can download if from HERE. I have pretty much stuck to the original document, certainly with the information.

Feel free to download and distribute as you wish but I take no responsibility for the accuracy of the information presented. Although I believe it to be correct, I suggest you verify it all before use.

Spectrum 48K BIT Diagram

I was recently part of a conversation on FaceBook regarding a couple of 48K Rubber Key Sinclair Spectrums. Both were proved to have faulty Upper RAM problems by issuing the command ‘CLEAR 65535’. Both machines reported ‘M Ramtop no Good’.

Ian Gledhill, of Mutant Caterpiller fame, was helping Francesco Morandin diagnose the problems. Ian went on to request Francesco issue the commands POKE 50000,85 then PRINT PEEK 50000 and POKE 50000,170 then PRINT PEEK 50000. By comparing the bit patterns expected to those that were reported, the individual ICs at fault could be found.

In this instance, Francesco got 85 for the first test and 186 on the second test for the first machine, then 213 for the first test and 170 for the second test on the second machine. So, working through:

If we then break the values down into binary:

I have underlined the bits that aren’t reporting correctly. After a quick exchange with Ian, I drew up a diagram to show what bits correspond to what ICs in the 48K Spectrum.

By finding the IC responsible for the mis-reporting bit, you can assertain whch one requires replacement. So, for the first of Francesco’s machines, IC19 is indicated as being faulty, and the second is IC22.

I have made a PDF of the diagnosis table which can be freely downloaded from HERE.

Co-incedentally, I have a 48K Spectrum with the same problem so I had the chance to use this technique for myself. I did the POKE/PEEK test and recieved 85 for the first test and 171 for the second test. Looking at the binary pattern for 171 (10101011) showed that bit 1 was reporting incorrectly. This indicates that IC15 is the culprit in this case. I have plans for this faulty machine to become a test bed so I’m not repairing it straight away.

A big thanks goes to Ian Gledhill for his insights and Francesco for posting his results.

Sinclair ZX Spectrum 48K Edge Connector Diagram

I’ve been using a faded copy of the original 48K manual for ages and in it is the diagram of the rear edge connector. I decided to redraw it.

You can also freely download a press quality PDF file from HERE

Sinclair ZX Spectrum 128K and 128K Plus 2 Edge Connector Diagram

I have added the 128K(Toasty) and Plus 2 PDF diagram HERE

Sinclair ZX Spectrum Plus 2A/2B and Plus 3 Edge Connector Diagram

And to complete the set, here’s the Plus 2A/2B and +3 PDF diagram HERE

Timex Sinclair TS2068 Edge Connector Diagram

Luis Guilherme asked if I’d do the TS2068

You can download a PDF copy of the diagram HERE

Timex Computer TC2068 Edge Connector Diagram

It wasn’t a lot of work to do the TC2068 since it shares the body shape of the TS2068

You can download a PDF copy of the diagram HERE

Sinclair ZX80 and ZX81 Edge Connector Diagrams

Just to complete the Sinclair edge connectors, heres the ZX80 and ZX81 diagrams.

The PDF versions of the diagrams can be downloaded from HERE (ZX80) and HERE (ZX81)

Slightly out of chronological order, however, I needed to draw the 48K Plus and 128K Plus ‘Toast Rack’ outlines for another project. I decided to complete the set properly:

And the latest machine, the Sinclair Spectrum Next

The PDF versions of the diagrams can be downloaded from HERE (48K Plus) and HERE (128K Plus ‘Toast Rack’)