ZX-128 broke down

Greetings, All! Help whoever can. One person burned Speck, instead of 5v he supplied 12v (wires confused). As a result, the following burned out: the processor, half of the VG (reads, but does not write), memory, AC remained intact, I don’t know about the ROM (there’s nowhere to check). I changed the processor, replaced all the memory, and took out a test ROM. I turn it on, the border on the screen is normal, and in the center on a white background there are 4 black ones parallel stripes, wide at the top, then 2 narrow, wide again at the bottom. When you remove the ROM and processor, nothing changes. Tell me where to dig next? Thanks in advance! All the best, All! Best wishes *** Sergey ***! >>

Hello Sergey! 19 Feb 03 09:22, Sergey Cherbynin -> All: SC> Help whoever can. One person burned Speck, instead of 5v he supplied 12v SC> (wires mixed up). As a result, it burned out: the processor, half of the VG SC> (reads, but does not write), memory, AU remained intact, I don’t know about the ROM SC> (nowhere to check). I changed the processor, replaced all the memory, got it out SC> test ROM. I turn it on, the border on the screen is normal, and in the center SC> white background 4 black parallel stripes, wide at the top, then 2 SC> narrow, bottom wide again. Nothing when pulling out the ROM and processor SC> does not change. Tell me where to dig next? Thanks in advance! Check the memory access node. Address multiplexers (KP11), read buffer (IR23), circuits for generating write/read signals (see for yourself ;) But first, pull out the percentage and check the levels of Sinhalese at all contacts. There must be a Z-state on the address bus, the same on all outputs of the processor, on the data bus - "1". The clock frequency must be supplied to the RESET, INT inputs and NMI the correct signals must be given. When you achieve all this by standing up a stone, but without ROM. The processor should immediately try to write bytes into memory.Ideally, a “mattress” of vertical white lines on a black background. But if there is such a “mattress” or something similar - then and insert the ROM. Alexand