The Sinclair QL Forum

The fault was in the ULA 8301. After the next replace this chip computer to start up.

The noise is initially present at 8301 of the order of 50-80 milivolts, it turned out that the RAS pin was bent. Unfortunately, in the variant of connecting any data bus to minus I checked only with the connected RAS pin. It will be necessary to look.

I checked all the slots in the first place. I am confused by the absence of the RAS signal and the lack of data flow after the IC21, although the IC21 itself is in good condition and there are impulses at all of its control outputs. By the way, when you put any of the data lines on, the other lines ...

All RAM is working properly.

Just according to the service manual, the RAS signal must be present both during the reading and during the data recording. In the same ZX, jon is approximately equal to the processor frequency, but it is inverted relative to it.

And such levels of signals on the pins of RAM are normal? Menerva ROM I do not have, so I'll have to solder the RAM chips. The first 5 for verification were in good order.

Do not tell what could be the problem. At the first turn on, the power LED was on, but the computer did not show any signs of life. The voltages on the board were all present but data exchange between the ROM-CPU-RAM was absent. I replaced the CLA2310 chip (ZX8301) and a white screen appeared. There...