Toshiba HX-10 Black Screen: What To Check?

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By PingPong

Prophet (3793)

PingPong's picture

28-07-2012, 18:52

jltursan wrote:

With a bad ROM, the HX-10 most probably would'nt boot to BASIC prompt.
Seems that there's a BAD VRAM ICs (4416), some characters have its bit 1 stuck to 0, there's also some others with bit 6 to 0. I don't know how they're mapped to their ICs; so it's a good measure to replace both VRAM ICs.

It's an easy replacement, you can use 4464 aswell, they're easier to find.

Yes, they have bit 0 and 6 not working correctly.
But why this problem does not affect even the charater pattern definitions?
Only bytes from name table are affected? This sound strange to me...

By jltursan

Prophet (2561)

jltursan's picture

28-07-2012, 19:00

True, maybe some of the glue logic around VRAM access is broken... Question

By bagpuss22

Supporter (6)

bagpuss22's picture

10-06-2013, 11:05

Well, I had exactly the same problem and a replacement LVA510 sorted it.

Does anyone know why so many of these IC's fail? I have bought extra just
in case I need to replace it again in the future.


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