New to MSX world (Casio MX-15)

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By dhau

Paragon (1570)

dhau's picture

18-04-2009, 23:27

Start with voltage checks on all ICs between Vcc and GND. You can find pinouts online. If voltage is ok (5V), try replacing electrolytic capacitors. They are usually rated for about 10 years of proper function. If voltage is mostly ok, but not on some chips, it could be bad pcb tracks. I had to find and fix a lot of fractured tracks on some very old and cheap pcbs from early 80s.

If all else fails, use the witch test. Set the thing on fire. If it burns, it's broken.

By Desperado

Rookie (22)

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18-04-2009, 23:58

OK, I uploaded it to imageshack:

http://img23.imageshack.us/img23/8767/casiomx15mainboard.png

Yeah, it's a little big I know.

The CPU is not visible by the way, as the smaller pcb is looted on top of the rest of the board and couldn't be removed from it. The pins are visible though.

By hap

Paragon (2039)

hap's picture

19-04-2009, 00:16

Ohh, another MSX with the evil Toshiba VDP Smile (bottom-left)
The partially visible chip is a GI AY-3-8910?

By Desperado

Rookie (22)

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19-04-2009, 00:26

GI AY-3-8910A

Need the bottom side of the board also?

By Desperado

Rookie (22)

Desperado's picture

21-05-2009, 21:48

Update:

I conducted a voltage check on the z80, the ram, anything on the top mounted PCB whrer the z80 is, T6950, the TV Out and the soundchips. The voltage ranged between 4.16 and 4.5 volt.

Still searching.

By Desperado

Rookie (22)

Desperado's picture

22-05-2009, 00:10

Another question:

There is something that looks like an adjustable capacitor on the bottom-left side on the pcb on my photo. That round white thing with the screw in it. The screen seems to change when I fiddle with it. What might it do?

By Manuel

Ascended (18396)

Manuel's picture

22-05-2009, 13:21

What do you see changing on the screen?

By Desperado

Rookie (22)

Desperado's picture

22-05-2009, 13:48

It seems that it's indeed an adjustable capacitor and it forms an oscillator in conjunction with a quartz. I accidently bypassed it yesterday which caused a bluescreen and some pixel garbarge.

Might it be possible, that someone tampered with clock frequency?

Another thing:
How can I identify the ROM where the Msx Bios ist stored in?

By Jipe

Paragon (1528)

Jipe's picture

22-05-2009, 13:49

the normal voltage is 5v to 5,20v
check your power supply before regulator

By Desperado

Rookie (22)

Desperado's picture

22-05-2009, 13:52

The power supply is labeled with an output of 4.5 V. Measuring directly at the connector confirms this value. The ICs get around 4.2-4.3 V.

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