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bubbo
April 18th, 2015, 06:45 AM
Hi to all
I hope somebody can point me in the right direction on this one.

Luckily I have 2 HX-10s One gives output to tv and the other does not .
Have eliminated the PAL conversion board by substitution.
I have already changed the CPU which is BAD
I have programmed a 27C256 and replaced the BAD Rom chip.
Now I have Data bit 4 ( Bit 5 of 8 ) stuck at High level on CPU ,Eprom and 4164 pin 2 .
Have taken all the socketed chips out still high.
I have cut ram pin and still high on board .( Now soldered it back ) will replace later.

SO I NEED A CIRCUIT DIAGRAM TO SEE WHAT ELSE SITS ON DATA BIT 4 .

My other I thought was 100% BUT the "D" key does not work .
De soldered and changed the key switch still no different . Checked with a meter and the switch works
so must be to do with scanning . But cannot find any other key that does not work.
So cct diagram a must if anyone can help.

Thanks

jltursan
April 22nd, 2015, 11:36 PM
Probably not very useful; but I have also find HX-10 machines with single non working keys and always has been the same: cold solder joints in the PCB. If the switch works, resolder it carefully and check the tracks continuity.

I've never seen the HX-10 schematics, the best resource in the net is http://msx.hansotten.com/index.php?page=msxmanuals. With a bit of luck, it'll be close to other MSX1 models, maybe you can trace back bit 4 signal.