ROM from Odea clone "Professional"

Hello Retrograde Ret> By the way, what could happen to the spec? I haven't measured the voltage yet. Maybe him Ret> and and is missing? /RESET is always at zero?

Hello icebear ice> /RESET is always at zero? It doesn’t look like, judging by the picture, a test has begun to check the amount of RAM, that is, the processor works. More like a bad contact of the ROM pins in the crib, a RAM malfunction, and a lot more :) But first you need to check the supply voltage, it is advisable to have from 4.9 to 5.2 V.

Hello Retrograde Ret> Yes, also: The voltage between the VCC and GND legs of the microcircuits is only Ret> 4.8 volts. Is it sagging? Ret> Ret> I just realized that the IR1s are heating up. I'll replace it tomorrow. Don’t rush to resolder the microcircuits; the logic rarely fails. First, check if any of the tracks on the board are shorted. Closure outputs of microcircuits may cause them to heat up. As I understand it, on IR1 shift registers have been made in the video controller, so if the screen is drawn is normal (and judging by the picture, it is normal), then IR1 is working. From the picture you can see that the computer freezes without completing the RAM test. Therefore, problems should be looked for primarily in the RAM chips, RAM address multiplexers and its buffer latches. 4.8 V is not enough for power supply, Some RU5 copies may be unstable. It's better if the food is not less than 4.9 and no more than 5.1. With 5.2, sometimes there are also failures in the RAM.