Splice Byte XD-300

This chess computer is a clone of the Fidelity Chess Challenger 7. It was manufactured by Splice Industria Brasileira between 1979 and the early 1980s. As far as I have been able to find out, it is the only chess computer manufactured in Brasil, so even as a clone it has a special value as a collector's item.

This unit did not turn on or, if it did, the 2 LEDs were on, but with nothing on the Display.

Disassembly and testing:

The voltage regulator is OK, and the 5V power supply is correct, too. There is clock signal, and the CPU seems to work fine. I also check that the Display driver is OK. I think the fault may be in the ROM or RAM bank.

Comparison between Fidelity CC7 and Byte XD-300:

The contents of both ROMs are dumped and compared: this is how to check if they are uncorrupted and, by the way, if they are identical to each other.

Many modern EPROM programmers cannot read this type of MaskROM.

I use a handmade adapter designed to read 2364 chips. The idea is to do the dump and use only the first 4KB of data.

Repair:

The fault is detected in the 2 sRAM chips (2111) of 256x4 Bit.

Assembly: