The Sinclair QL Forum

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 is data exchange between the ROM and the Processor, but on all the RAM chips there are no pulses at 2 and 14 pins (high level). Also on the conclusions of RAM there are pulses on the 3rd pin (WE) and the address pins, but the signals (RAS) are absent (low level) and the signals (CAS) in the first bank are 0 volts on the second 5 volts. It seems to indicate the incorrect operation of the newly replaced chip and IC21. IC21 I replace, but the malfunction did not go away. Could the CLA 2310 be defective again, but already on the RAM control line or the fault further in the circuit? Version of computer ISS.6.

A white screen is usually a ram issue

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.

Sadly that is the limit of my knowledge, but I'm sure someone else will know

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.

Welcome to the forum btw

All RAM is working properly.

I've split this into it's own topic, so hopefully more people will see

A white screen can also indicate that one of the pins in the expansion slot is bent and touching another (a common fault especially when Trump Cards were being removed and inserted!)

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 show impulses, but the RAS signal, although it appears but the range is only 2 volts, seems to be very noisy.