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Diagnostic ROM for Toshiba HX-10?

By grahamn

Supporter (2)

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25-09-2019, 16:44

Hi

I have been repairing vintage computers for many years now, but have fairly limited experience with MSX machines (something I am trying to remedy!). I've repaired a few with RAM and ROM issues, but I have one now that is currently beating me and I've been searching for diagnostic ROMs or service information. So far I've not found anything suitable - can anyone tell me if anything like this exists?

I have found a TESTROM program, but no information on it - I assume it can be burnt to an EPROM and will replace the exiting ROM, but I don't know for sure, and in any case the machine I'm currently working on (a Toshiba HX-10) is just giving a black screen. I have a spare video board and changing that makes no difference. I also found a 4116 RAM chip that looked bad so changed that without result.

I've swapped out the socketed chips, but can't see anything obviously wrong. I'm tempted to blanket replace the RAM, but don't really want to do that just on a whim.

Any help / advice would be most welcome.

Thanks

Graham

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By grahamn

Supporter (2)

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25-09-2019, 22:43

Just an update on this. I decided to bite the bullet and unsolder both the RAM and video RAM and fit sockets. I replaced the RAM with kown good chips and still just got a black screen.

As I've now tried swapping out all the RAM, ROM, CPU, Video and Sound chips as well as the seperate video board, I guess I'm just left with the Toshiba 64 pin chip (ULA?)

I should add that all voltages look fine (+5V, -5V, +12V)

i'm assuming the Toshiba chip is unavailable as a spare part unless anyone knows a source?

Thanks

Graham

By Wierzbowsky

Guardian (3649)

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26-09-2019, 10:37

Nope, you can get this chip only from a broken Toshiba's motherboard. If you would like to sell your broken computer, I would be willing to buy it.

By gdx

Enlighted (6438)

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27-09-2019, 09:49

I saw some people with this issue and it could increase over time. I hope someday someone will make a replacement chip. A Korean has already done it for the DW64MX1 so it's possible.

By l_oliveira

Hero (534)

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08-10-2019, 14:47

A thing you can manufacture to aid your repair process is a 64KB RAM cartridge. It's actually simple to craft such a device with a SRAM, for example. You can pick a 128KB chip such the HM628128 and use half of it for 64KB. You can use any MSX ROM cartridge with all gold fingers present, wire the SRAM straight to the slot and the MSX can detect and use it as mainram. That will allow you to boot any MSX computer (any but the MSX Turbo R which does not boot from RAM in the slots) with failed work ram.

By Gregory

Champion (295)

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14-07-2021, 22:04

l_oliveira wrote:

A thing you can manufacture to aid your repair process is a 64KB RAM cartridge. It's actually simple to craft such a device with a SRAM, for example. You can pick a 128KB chip such the HM628128 and use half of it for 64KB. You can use any MSX ROM cartridge with all gold fingers present, wire the SRAM straight to the slot and the MSX can detect and use it as mainram. That will allow you to boot any MSX computer (any but the MSX Turbo R which does not boot from RAM in the slots) with failed work ram.

Would you happen to have schematic for this? Or something that is commercially available?