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Author Topic: VERY Dim video output from Amiga 4000  (Read 4472 times)

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Offline Boing-ball

Re: VERY Dim video output from Amiga 4000
« on: April 28, 2024, 06:03:52 PM »
Before making this video, please watch (this section) as you'll get an idea of the issue....

Amiga 4000: Is the Fastlane Z3 the best home for a BlueSCSIv2 Upgrade?

When I filmed that, I had to post process it A LOT to increase its brightness to acceptable levels for this video. I had assumed that the issue was to do with the RGB to SCART cable (unlikely) or that my trusty SAMSUNG LED with SCART was on its way out (more likely).

However, today, I tested this by plugging in my A500, and the video looks bright and clear, as I remember it. So, A4000 has a problem  ::).

Calling on the ancient wisdom of the Amiga collective. Would anyone know what this is a symptom of?

My guess, if I were someone else, would be that capacitors were going down the swaney, and providing too low voltage. However, I had this machine re-capped just last year. So its very unlikely this is the issue. However, the recap was because of some leakage in the video area, however, I was lucky in that it seemed to be early days. I have cleaned that area, so Im surprised if its on-going corrosion.

Anyway, over to you guys. Wondering if Christ Edwards lurks here, as I would assume he might recognise the issue...

Could be the Video DAC.

Worth a look here:

https://www.amigawiki.org/doku.php?id=en:parts:video_dac

It maybe a corroded trace from the Caps leakage.
 

Offline Boing-ball

Re: VERY Dim video output from Amiga 4000
« Reply #1 on: April 29, 2024, 01:51:25 AM »
If you read my post, it says, if I were someone else. i.e. I was anticipating others telling me that it is a capacitor issue.

But in my case, I know its nothing to do with capacitors, as they are all new. Now, could it be failing resistors? Im not sure, as I am not an electronics student.

As you say, its certainly got something to do with the DAC you might assume.

Ill take a look at it, and see if anything sticks out. I do hope its NOT the chip itself, as it will be a tricky replacement,  but lets see.

If it is the Chip and you don’t want to attempt the replacement. Then give Ian a shout at mutant-caterpillar based in Anglesey North Wales.