Sony HB-F1 no keyboard input at all

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By Dr.Wily

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21-02-2018, 12:36

Ah yes interesting result, only 28 Kb free on a total of 64 kb.

By gdx

Prophet (2056)

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21-02-2018, 12:46

This is normal. Find a way to test RAM.
It is possible that it is the ROM which is defective. Do you have the material to write an eeprom?

By Dr.Wily

Supporter (16)

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21-02-2018, 14:20

Yes I can write eeprom and I will receive a RAM cart in few days for further tests.

About writing a new firmware, I need a compatible eeprom but I can't find datasheet for a LH531083 maskrom.

On the mobo I suppose this chip is the firmware.

By NYYRIKKI

Enlighted (4936)

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21-02-2018, 14:29

Dr.Wily wrote:

Ah yes interesting result, only 28 Kb free on a total of 64 kb.

Yes, this seems very ok... I think this should not look ok if the RAM would be dead... and still the computer is completely unresponsive? or can you write something on BASIC? I'm starting to think again it might be bit rot on the ROM.

By Dr.Wily

Supporter (16)

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21-02-2018, 14:36

Keyboard is responsive at boot since I have credit screen with Y&P keys and BASIC with DEL key. After that there is no way the get a valid input. No response of any key. I think the MSX is totally frozen.

By NYYRIKKI

Enlighted (4936)

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21-02-2018, 14:53

Dr.Wily wrote:

On the mobo I suppose this chip is the firmware.

Yes, that's it... I think you might find this post very interesting.

By gdx

Prophet (2056)

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22-02-2018, 09:25

About Rom I think pinout is same as LH531000 series.
http://pdf.datasheetcatalog.com/datasheet/Sharp/mXvttvr.pdf

You can use a eeprom 27C512 if you remove the firmware, pinout is compatible.
https://www.jaapsch.net/psion/pdffiles/Eprom064k_datasheet_2...

It's probably same method as Panasonic FS-A1. Just write Main-ROM + Sub-ROM + 16kB of FFh (in same order). That's what I did for my FS-A1.

By Dr.Wily

Supporter (16)

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22-02-2018, 13:07

OK, got a 8kb RAM cart... but nothing change with this cartridge inserted in slot 1 or 2. Maybe I must make others tests ?

Quote:

It's probably same method as Panasonic FS-A1. Just write Main-ROM + Sub-ROM + 16kB of FFh (in same order). That's what I did for my FS-A1.

I have this set of ROM but I don't understand how to burn it, because it's divided in multiples parts. I never worked on MSX before, I'm not familiar with this hardware.

By gdx

Prophet (2056)

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22-02-2018, 14:46

MSX2+ can't work with the 8kB RAM cartridge. It is specific for Casio's MSX.

Use a Hexa editor to assemble the parts. Main-ROM + Sub-ROM + 16kB of FFh = 64kB.
You can also use CONCAT.

By Dr.Wily

Supporter (16)

Dr.Wily's picture

23-02-2018, 14:47

Ok I have advanced on this repair. I was able to use the keyboard and it's not a rot in maskrom. This is a bad contact somewhere on the mobo.

To make it works I checked all ceramic capacitors to avoid a short circuit with strapping wires or bad contact and... the MSX back to life. I have an animated sony/hibit logo on menu screen and full keyboard control.

But when I reassembled, the issue back again. I searched, but can't find incorrect contact / component.

Here his the behavior of the MSX when it works :
- MSX logo come up, even when the speed slider is unpluged from CN7 connector. (when it's unpluged, MSX logo is animated more slowly)
- On menu there is an animated sony/hi-bit logo
- keyboard works

When it's does not works :
- MSX logo come up only if the slider (or a jumper) is plugged on CN7 connector. otherwise it's a black screen.
- On menu, animated sony/hi-bit logo remains stuck on "Sony"
- no keyboard input.

Z80 and V9938 are supply with a solid 5v. Any tips ?

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