Toshiba HX-10, not working.

Page 3/3
1 | 2 |

By llopis

Rookie (26)

llopis's picture

28-01-2019, 10:11

RetroTechie wrote:

DRAM control can be done in several ways (early write, hidden refresh.. it's complicated). But usually, /CAS signal(s) work like a chip select. So remaining high just means that DRAM isn't asked to write or output (read) anything. Which can happen if eg. a faulty ROM causes the machine to get stuck in a loop. Or some other issue makes the machine not get to the point where it searches for / uses the RAM.

But wouldn't a healthy Z80 always be fetching instruction data if it's getting a clock signal? Even if it's in a loop, it should be constantly fetching from memory, right?

By llopis

Rookie (26)

llopis's picture

12-09-2019, 11:29

Just to give this some closure: I ended up tracking down a working Toshiba HX-10 and started reverse-engineering the circuit diagram and checking things on both. Everything checked fine and I didn't see any obvious problems with the faulty one. I also swapped all socketed ICs just in case, but nothing.
So I decided to desolder and socket the TCX-1007 (which is the big custom IC) and... bingo. That was the problem :-(
Anybody knows where I can buy a TCX-1007 or am I out of luck with that machine?

By Alexey

Guardian (2285)

Alexey's picture

12-09-2019, 12:19

This chip seems to be the MSX engine of Toshiba. The only way to repair the machine is to get a broken motherboard with the working chip. I could buy the broken Toshiba from you if you decide to sell.

Page 3/3
1 | 2 |