Help fixing Vector-06c

[cyb2600]

I powered on the Vector and see the checkerboard and hear buzzing and "rus" light is on.

I pressed "VVOD" and "BLK" simultaneously. The screen goes black, the "rus" light turns off, the buzzing stops, and I hear the relay go click.

I play the "testtp.rom" and hear the tones on the Vector06-c speaker.

When it's done playing the LED doesn't flash and the screen stays black.

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[KTSerg]

I powered on the Vector and see the checkerboard and hear buzzing and "rus" light is on.

I pressed "VVOD" and "BLK" simultaneously. The screen goes black, the "rus" light turns off, the buzzing stops, and I hear the relay go click.

I play the "testtp.rom" and hear the tones on the Vector06-c speaker.

When it's done playing the LED doesn't flash and the screen stays black.

The checkerboard, when turned on, indicates that the image is formed correctly. This is typical of Vector, which does not autostart on power-up.
But until the download grid appears, yellow on a blue background, the program from the tape recorder will not load.
There is a suspicion that the bootloader checks the memory, then detects an error and loops on this test.

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I believe one should test memory.
Since the bootloader cannot be used, there are two options: either change the bootloader microcircuit to another, into which to write the memory test; or connect an external bootloader microcircuit to the long "ВУ" connector, which is much more difficult.

[x-code]

There is a suspicion that the bootloader checks the memory, then detects an error and loops on this test

Are you sure that the bootloader has a built-in RAM test? Never heard of this before...

Still, the bootloader uses the upper RAM for its stack and variables (0xe000-0xffff). Coincidentally, this is also the upper bank of the video frame buffer - the only one used by the bootloader in order to reserve all RAM below 0xe000 for loading programs (hence the pixel "garbage" in the upper right corner of the bootloader grid screen)

So if the corresponding memory chips are corrupted or do not receive proper signals, neither the grid will be visible nor the bootloader will be able to operate normally.

Also, it's strange that you can hear signal coming to the tape input from the speaker. I cannot recall this being the case, as the tape input should go directly to the comparator circuitry.

I would double-check if you are not mistakenly using tape out instead of tape in.

Could be a quirk of the early motherboard revision you have, though.

[KTSerg]

Are you sure that the bootloader has a built-in RAM test? Never heard of this before...

Это самое начало штатного заводского загрузчика.

Скрытый текст

...
        LXI     SP,0DCF0H
        LXI     D,55AAH
M000EH: PUSH    D
        POP     H
        MOV     A,L
        CMA
        CMP     H
        JNZ     M000EH
...

[свернуть]

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I cleaned all three areas up with rubbing alcohol until they were shiny, and I verified none of the traces were broken from corrosion. Unfortunately it didn't make any difference.

I didn't talk about corrosion. The conductors run next to the mounting holes. They are often crushed, and neighboring ones are connected to each other.