Flickering Screen On A1200...

[Franko]

Never came across this problem before...

On an old A1200 I bought from eBay (MB Rev 1D.4) any access made by the floppy or HD causes an annoying flicker all over the screen...

I've tested it in turn with  the HD, Floppy and extra ram board disconnected and 5 different power supplies but the result is the same each time, this annoying background flicker on the screen (whether in composite or RGB)...

Anyone came across this problem before or have any ideas about the cause of it...

Cheers

Franko

[tone007]

I have had that problem on a couple of units.  Supposedly there was some fix adding a capacitor somewhere on the board, but I never bothered.

edit: http://mysite.verizon.net/jartz/amiga/amiga.html, search for flickfix.

edit again: same one here, I think: http://aminet.net/package/docs/hard/flickfix

[Kesa]

Hmmm... a flicker from an amiga...

... and then its owner feels warm inside.

Maybe it's just flirting with you? *Franko blushes*

:roflmao:

[Franko]

I've got 4 other REV 1d.4 boards never seen this problem on them though, oh well another Amiga goes to heaven...

Hmmm... Kesa's typing something now... wonder what pearl of wisdom he'll offer...

(@ Kesa, kinda suspected something like that... )

[tone007]

Maybe it just needs new capacitors in general.

[Franko]

Maybe... I'll runs some tests on it tomorrow and check it against some of my other ones, no big loss really...

[RMK305]

Mine does this also. Maybe it's Scottish electricity?

[Franko]

Hopefully I've found the answer in a post on EAB, gonna give it a try tomorrow...

Flickering Screen On A1200

[ElPolloDiabl]

It might be the power connector socket on the A1200 is loose. It's not grounding properly.

[Franko]

It might be the power connector socket on the A1200 is loose. It's not grounding properly.

Gave all the connections and solder joints a thorough check with a large magnifying glass, everything looks ok. The boards actually in near mint condition the previous owner said it had been lying in his loft for the past 12 years, so hopefully it's just some caps that have dried out...thanks anyway...

[tone007]

Hopefully I've found the answer in a post on EAB, gonna give it a try tomorrow...

Flickering Screen On A1200

That's the same fix I posted above, though their picture is better!

[Franko]

Did you ever give it a try tone... did it work...

[tone007]

I don't think I actually tried it, I seem to recall using a different power supply with a large ferrite bead lessening the issue enough for me.  However, so far that's two people who've used it and had luck!

[TjLaZer]

I have one doing the same thing!  Hi-Res or interlace screens it flickers like crazy when there is disk or HD access!  Lo Res its fine!  Gotta try this hack.

[Merc]

I have one doing the same thing!  Hi-Res or interlace screens it flickers like crazy when there is disk or HD access!  Lo Res its fine!  Gotta try this hack.

My brother's old A1200 had this problem -- it was a bug in that particular board revision I think, mine didn't have the issue.  The fix?  Eliminate any colours in the screen's palette set to 255,255,255 (full white)!!  Bizarre, I know, but it did the trick for his machine -- he even wrote a little daemon to monitor the palette of the top screen and adjust to 254,254,254 any such offending colours!