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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: hcoder on April 24, 2023, 07:32:22 PM

Title: Amiga 4000 no video using A520
Post by: hcoder on April 24, 2023, 07:32:22 PM: Hi,

I'm in the middle of a recap process and I changed a few caps. They all measure OK and everything seems fine.
I'm using an A4000, 030 and Chipmem. The rest is all unplugged. The motherboard is removed from the case and placed on my desk.

When I first booted the machine it all went to the kickstart screen (OS 3.1) and the floppy was inserted a few times.
Suddenly the screen turned funny and then to black.

When I turn the machine off and back on this is what I can see:

1: The TV receives a signal, it shows a black screen
2: After about 30 seconds (the moment of the kickstart screen?) the screen changes to darker black with a moving white bar moving from bottom to up, repeats
3: That's it.

The A520 I'm using is 100% as my A1200 works perfectly with it.

Anyone has a clue what might be the problem?
Every reboot results in the above problem.
Title: Re: Amiga 4000 no video using A520
Post by: Pat the Cat on June 10, 2023, 05:14:59 PM: AFAIK the A520 does not work with "big box" Amigas due to them having an unbuffered video output on the 23 pin video connector.

A2000, A3000 and A4000 all have video slots which is maybe the root cause of them having unbuffered outputs? Not sure.

EDIT: The above is true for PAL systems, I don't know if it's true for NTSC. Because the A520 came in both flavours of video.
Title: Re: Amiga 4000 no video using A520
Post by: jaesonk on July 07, 2023, 11:10:14 PM: I don't recall if the A520 works with big box Amigas or not, as previously stated in another reply, but I'm pretty sure I used one with my A3000D. I don't have one to try with my A4000 now.

Check to make sure you're using NTSC with NTSC or PAL with PAL. The A520 will only work with those screenmodes and the appropriate TV or monitor.

Try cleaning the A4000 video socket and A520 connectors with deoxit or wd40 specialist (the one for electronics, not the penetrating lubricant).

Once in a while I come across a video cable with intermittent connection. Bend it one way and it works, bump it another way and it doesnt.
Title: Re: Amiga 4000 no video using A520
Post by: RobertB on July 08, 2023, 03:26:51 AM: Quote from: Pat the Cat on June 10, 2023, 05:14:59 PM
AFAIK the A520 does not work with "big box" Amigas due to them having an unbuffered video output on the 23 pin video connector.

A2000, A3000 and A4000 all have video slots which is maybe the root cause of them having unbuffered outputs? Not sure.
I used an A520 with an A2000, and it locked up all mouse movement! As soon as the A520 was removed, mouse control came back.

Truly,
Robert Bernardo
Fresno Commodore User Group - http://www.dickestel.com/fcug.htm
Southern California Commodore & Amiga Network - http://www.portcommodore.com/sccan
Title: Re: Amiga 4000 no video using A520
Post by: Examigan on July 09, 2023, 11:27:09 AM: I am nearly 100% sure I used one back in the early 90s with my A2000 and it worked OK.
Title: Re: Amiga 4000 no video using A520
Post by: Robbie on August 07, 2023, 01:46:23 PM: I remember attempting to use one on my A2000 and it not working. Perhaps it is a problem with PAL Amigas then?