Possibly broken RAM

[spicy]

Hi,


After many years, I have tried to start my old CPC464 (Schneider version), but it didn't work. Especially the monitor behaved funny (weird high pitch sound coming out of it). Also no sound action on certain keyboard presses (so not only a problem with the screen).


I tried to start the CPC with an external 5V power supply and a GBS-8200 board, but I only get to the white/gray screen with black border. This seems to be consistent with an IC failure (mostly RAM if I look at this discussion board).


After opening it, I did found the RAM chips on IC117 and IC120 to be quite hot after 1 minute (+60°C), while other chips stay cool.
Is there any other way to test the other IC's?


Now my question: I see that my CPC uses MT4264-15 memory ICs, while most post mentions the (x)4164 part. Is there a a difference between these two chips? Both seems to be 64Kbits, but I don't find anything about cross compatibility. Can 4164 and 4264 be used together, should all be 4264 or 4164. Can a CPC which has the 4264 chips be fitted with 4164 IC's without further modification?


It seems both the 4264 and 4164 is available dirt cheap through aliexpress (I'm not sure what crap they will send)