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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Kernel on May 27, 2011, 04:17:01 PM

Title: A3000 Pixel Jitter
Post by: Kernel on May 27, 2011, 04:17:01 PM

I have sparkles all over my desktop.  YAY!

I know I can adjust this with the fine tuner and a small phillips screwdriver (I don't have the actual tool that came with the A3000) but I've done this in the past and it just comes back eventually.  I figure this will be gone once I land that elusive Picasso IV card, but until then, I'm wondering if anyone has ever had to adjust the "coarse" setting that is mentioned in the manual as not user adjustable?  I'm assuming that this would be the other small phillips based pentomiter on the motherboard near the Amber chip area.

Anyone have thoughts on this?

Title: Re: A3000 Pixel Jitter
Post by: Zac67 on May 27, 2011, 04:56:06 PM

I don't think you'll ever need to use the coarse adjust. It'll probably make you lose some of the overscan capabilities of Amber which it normally shines with.

Title: Re: A3000 Pixel Jitter
Post by: hardlink on May 27, 2011, 10:09:04 PM

Quote from: Kernel;640602

I have sparkles all over my desktop.  YAY!
Anyone have thoughts on this?

Then there is always the old U202 and U203 PAL problems, which my A3000 has:

http://www.zimmers.net/cbmpics/cbm/amiga/a3000guide.txt

Title: Re: A3000 Pixel Jitter
Post by: Kernel on May 30, 2011, 07:53:07 PM

Quote from: hardlink;640753

Then there is always the old U202 and U203 PAL problems, which my A3000 has:

http://www.zimmers.net/cbmpics/cbm/amiga/a3000guide.txt

Well, I fixed the sparkles/jitter with a few twists of the fine tune but I'm sure it will return eventually.

I'm not sure if my issue is what you identified here but does anyone know if this sparkle/jitter issue can be cleaned up by replacing the above chips, Amber, or other chips?

Title: Re: A3000 Pixel Jitter
Post by: mechy on May 30, 2011, 10:26:50 PM

Quote from: Kernel;641425

Well, I fixed the sparkles/jitter with a few twists of the fine tune but I'm sure it will return eventually.

I'm not sure if my issue is what you identified here but does anyone know if this sparkle/jitter issue can be cleaned up by replacing the above chips, Amber, or other chips?

I doubt you have a chip problem,because adjusting it brings it back. its more than likely that the variable resistor and the wiper is old/worn/corroded inside. Replacing that potentiometer may solve it. Other things that could cause it are chips that need reseating,tarnished sockets,power supply and the pal's as mentioned above. you can glue some small heatsinks on the pals and see if it helps,they run very hot(or replace with GALS) and if its a issue of PAL chip heating this may fix it..

mech

Title: Re: A3000 Pixel Jitter
Post by: Ral-Clan on June 01, 2011, 09:30:43 PM

I agree that the potentiometer (the thing you adjust) is probably just dirty.  If there is any way to spray contact cleaner (TV tuner contact cleaner) inside it (inside the actual potentiometer) and give it a few twists to clean the dirt, that might remedy the problem.

Title: Re: A3000 Pixel Jitter
Post by: Kernel on June 01, 2011, 11:40:16 PM

Ah - yeah, I'll try a bit of that!

Title: Re: A3000 Pixel Jitter
Post by: Plaz on June 01, 2011, 11:58:18 PM

Electrolitic caps have a limited lifespan. Any originals on your board are now ~20 years old and could be part of your problem. Same goes for the power supply. Weak caps or drifting power supply could be at the root of the problem.

Plaz

Title: Re: A3000 Pixel Jitter
Post by: magnetic on June 01, 2011, 11:59:21 PM

kernel

Let us know how any repairs/cleaning go.. I've had a lot of a3000 in for repair or resale that have had this problem.

Title: Re: A3000 Pixel Jitter
Post by: Plaz on June 02, 2011, 03:51:23 AM

Quote from: magnetic

Let us know how any repairs/cleaning go.. I've had a lot of a3000 in for repair or resale that have had this problem.

I've cured several over the years based on the info above, including 2 of my own. Pretty common video problem in many arcade cabinets I've done also.

Plaz