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Author Topic: A1200 Sudden video problem  (Read 948 times)

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Offline mykrowyreTopic starter

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A1200 Sudden video problem
« on: September 26, 2023, 03:34:12 PM »
I finally have another A1200 in my hands after 20 years, and it's been amazing. 

However, I started having random keyboard freezes only on a few keys, as if something was hammering an interrupt. I would lose only certain keys such as L and a few others on the right side of the keyboard. They would come and go in bursts.

I removed my accelerator and still had the problem so I figured it must be time to re-cap this amiga.

Then, the keyboard problem went away completely, and instead I am left with jail bars on the screen. Amiga runs fine but the video now has faint jail bars similar to the C64.  I suspect this was a capacitor shorting and I'm hoping it didn't just damage my video chip but hoping this is just ripple now left unfiltered.

I have a cap kit on the way, but was just curious if anyone else had seen this scenario unfold and identified the culprit?

Thanks

« Last Edit: September 26, 2023, 03:38:29 PM by mykrowyre »
 

Offline PlatformerZ

Re: A1200 Sudden video problem
« Reply #1 on: September 26, 2023, 10:33:40 PM »
If you are using a scandoubler or tft/lcd monitor, a buffered DB23 adapter on the RGB port can eliminate the jailbar effect. You might be getting better voltages with the new caps and this is bringing out further inconsistencies between the Amiga and display.
 

Offline mykrowyreTopic starter

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Re: A1200 Sudden video problem
« Reply #2 on: September 27, 2023, 03:15:24 AM »
Ok I figured out the video issue... it's only visible when I am in PAL screen mode (NTSC amiga).  When I switch back to NTSC Hires, it's gone.

The keyboard problem is back again, going thru everything now to see if it's something simple.
 

Offline scuzzb494

Re: A1200 Sudden video problem
« Reply #3 on: October 03, 2023, 03:43:47 AM »
Check that the ribbon is square in its slot and that the clip is seated tight. Never pull the ribbon out with the clip latched. Always retract the latch before extracting the ribbon. I have a similar problem with an Escom machine I have but its kinda my fault as I don't have the top case screwed down and the keyboard moves around a bit. But if the ribbon moves out of square I lose various keys and the space bar often. Just reseating it fixes the issue. Worth a shot. Also cleaning the connector may help but don't abrade or cut or scratch the surface. Also remember which way you took the clip off cus if fitted the wrong way will render the keyboard dumb.

Offline mykrowyreTopic starter

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Re: A1200 Sudden video problem
« Reply #4 on: October 10, 2023, 02:16:23 AM »
I fixed the keyboard problem lol

https://www.youtube.com/watch?v=zjF7ibCXMHU