A4 laptop - no display

Arc/RPCs, peripherals, RISCOS operating system & ARM kit eg GP2x, BeagleBoard
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mattdy4
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A4 laptop - no display

Post by mattdy4 » Wed May 15, 2019 8:15 pm

Picked up an A4 laptop cheaply months ago but only just got around to taking a look at it as I had to purchase a PSU for it. Surprisingly it powered up but that was really about it. Ocassionally the keyboard LEDs would illuminate but they stay on unresponsively but the HD would occassionally kick in.

Opening up there was very little to no CMOS battery damage but removed the battery anyway as was only giving .6v, cleaned and replaced with a AAA holder on wires and soldered in a new 8583T for good measure. Reconnected and still nothing. Worth a shot though.

Some of the caps looked suspect, especially to the right hand side of the board, so I replaced all of them. Once removed the caps in the bottom right had all leaked and the whole board needed a good clean before a recap.

Reassembled the A4 with external keyboard, external monitor, LED screen and it now boots - or at least seems to! Resetting CMOS makes the ext keyboard flash twice and the floppy drive checks for a floppy (no codes given). All keys seem to respond. The external monitor recieves a VSYNC and stays that way but the image is grey. LCD shows nothing but could be dead I guess. Keyboard responds and can CTRL+BREAK with effect and can see the external monitor go dark grey/black/dark grey. Tried blind *configure monitortype 4 / 5 / 0 etc but nothing.

Pretty much out of ideas at this point

RobC
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Re: A4 laptop - no display

Post by RobC » Wed May 15, 2019 9:21 pm

What happens if you do F12 then press copy (or go into BASIC and do VDU 7)? Do you get the bell sound?

If that's working, I'd definitely concentrate on getting it working with an external monitor. Have you tried configuring the sync setting?

Good luck with this - A4s are a pain to work on and the FFC cables and connectors are easily damaged :(

mattdy4
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Joined: Mon Feb 26, 2018 11:18 am
Location: Wolverhampton
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Re: A4 laptop - no display

Post by mattdy4 » Wed May 22, 2019 11:20 am

No sound at all. Guessing its something around the VIDC chip rather than the chip itself but TRM not giving much away. Ideally I could do with a circuit level diagram which I haven't found for the A4 yet

I've already slightly damaged the floppy connector with hot air!

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