Author Topic: Amstrad 6128 problem  (Read 1238 times)

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Offline johnny

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Amstrad 6128 problem
« on: 18:59, 23 July 10 »
Hello,
I've just bought my first Amstrad 6128 on ebay. It almost works correct :)
After turn on computer type itself different symbols: letters (specially greek), numerals, dots, and  etc on the monitor. I can't type from keybord. Keyboard foil looks good - that is beside the point - without foil effect is the same. On the PCB one IC has been replaced. It's IC107 - now it's intel P8255A-5, A0615.
Sometimes after turn on computer work 100% properly, I can type, I can run game from drive 3' drive. After a few minuts of gaming - connection with joystick is reset, end of fun.
Sometimes if I press PCB (amstrad is on) strange side-effect stops, and computer is ok. I've adjusted all solders of IC107. No effect. Is that IC damaged? Maybe something other?
Can you help me?

Offline arnoldemu

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Re: Amstrad 6128 problem
« Reply #1 on: 19:16, 23 July 10 »
Hello,
I've just bought my first Amstrad 6128 on ebay. It almost works correct :)
After turn on computer type itself different symbols: letters (specially greek), numerals, dots, and  etc on the monitor. I can't type from keybord. Keyboard foil looks good - that is beside the point - without foil effect is the same. On the PCB one IC has been replaced. It's IC107 - now it's intel P8255A-5, A0615.
Sometimes after turn on computer work 100% properly, I can type, I can run game from drive 3' drive. After a few minuts of gaming - connection with joystick is reset, end of fun.
Sometimes if I press PCB (amstrad is on) strange side-effect stops, and computer is ok. I've adjusted all solders of IC107. No effect. Is that IC damaged? Maybe something other?
Can you help me?
Keyboard is read using 8255 and AY-3-8912.
And there is a 74LS IC (can't remember number).
Check the connections on the other two.

EDIT: 74LS145

EDIT2: You may even try checking solder on 6845 too. This provides vsync and hsync. If vsync is missing firmware may not even scan keyboard.
« Last Edit: 19:21, 23 July 10 by arnoldemu »
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Offline johnny

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Re: Amstrad 6128 problem
« Reply #2 on: 20:56, 23 July 10 »
Done. It looks good. Probably problem was with connection 37 pin of IC 107 witch 21 pin IC 102 (AY-3-9812). I hope it fixed ... :)
THANK YOU VERY MUCH !!!
regards
johnny