Canon V-20

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Por MKuosma

Supporter (8)

Imagen del MKuosma

09-11-2008, 21:11

Hello all,

I have a problem with my Canon V-20. It shows only black picture when it's on. There is also no sound and it seems to be totally dead. Caps Lock led doesn't lid.

I've tried to figure out what's broken, but haven't find anything yet. Video seems to be ok when measuring it with the oscilloscope. Processor Z80 reads something from and seems to receive something from circuit which is made by Microsoft. After that the processor tries to read something but doesn't receive anything.

If anyone has any ideas what could be wrong or broken please let me know.

Thank you in advance for the help..

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Por Jipe

Paragon (1594)

Imagen del Jipe

09-11-2008, 22:09

check your ram in the V20 is often broken
you can desold memory chip and put a memory cartridge in slot for rapid check

Por MKuosma

Supporter (8)

Imagen del MKuosma

10-11-2008, 08:21

Ok. Thank you very much. I'll try that..

Por MKuosma

Supporter (8)

Imagen del MKuosma

10-11-2008, 19:44

One additional question. Just to make sure as i don't have Canon V-20 schematics (just SVI-328 schematics which seems to be quite same). Is it so that 4164C-15 are ram?

Por MKuosma

Supporter (8)

Imagen del MKuosma

26-11-2008, 15:49

Hello all,

I changed all ram (4164) chips, but it didn't help. I can still see only black picture. If anyone has any ideas what could be causing the problem could you please let me know? Also it would be great to have the schematics for V20.

Thank you in advance for the help..

Por Jipe

Paragon (1594)

Imagen del Jipe

26-11-2008, 17:34

have you checked power supply +5v +12v -12v
you can find it on the cartridge connector

41 43 GND
45 47 +5v
48 +12v
50 -12v

Por MKuosma

Supporter (8)

Imagen del MKuosma

26-11-2008, 18:25

Hi,

Thanks for your reply! Just checked with your instructions. Power supply seems to be ok. Any other ideas?

Por Jipe

Paragon (1594)

Imagen del Jipe

26-11-2008, 19:14

when the rom is broken the CPU live
you can see pulse on adress signal with the scope
can you replace the ROM ?
you can found the canon v20 rom for the OpenMSX emulator and burn in eprom

Por MKuosma

Supporter (8)

Imagen del MKuosma

26-11-2008, 19:24

CPU is replaced and it should be ok. Eprom would be harder to change for me as i don't have equipment to burn it. With the scope i cannot see the address signal, bit cpu's read signal is active.

Por MKuosma

Supporter (8)

Imagen del MKuosma

26-11-2008, 19:33

In case i can find someone to burn the eprom for me, could you send me the type of rom circuit i could use? I assume the rom chips is the one made by Microsoft. Please correct me if i'm wrong. I tried to find some information (datasheet) about it, but could not find anything.

Por Jipe

Paragon (1594)

Imagen del Jipe

26-11-2008, 20:07

clip on Jipe at the left of this box
you can see my e-mail
send me a e-mail and in send you the file for burning eprom

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