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Old 21 June 2019, 06:06   #1
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Amiga 2000 - RGB to VGA issue

I recently got my hands on an Amiga 500 and a 2000. I also got myself an RGB to VGA adapter from Vintage Systems in Poland.

The 500 works well with most screens I have tried.

The 2000 however does not. If an attached lcd is turned on, she powers up but does not boot (no floppy activity). Sometimes the caps lock does a single blink per second which I think means rom check failed. If caps lock doesn't flash, it is toggle-able. The power light doesn't flash at all, it is always solid green.

If I turn the lcd off or use a mechanical kvm to switch the screen away, it does boot, but this is a pain.

I saw the 2000 running with an original Commodore monitor and it booted successfully a few times.

Mono out and audio work fine.

The 2000 has a gotek installed. For a few attempts, I was able to boot from real floppy but not the gotek. Now I can't get to kickstart at all while the screen is on. I have also tested with the gotek completely disconnected, to no avail. But the gotek does work as long as I boot with the screen off.

I have removed the only card, an A2091 to no avail.

I found some info on J200:
This jumper determines the time base used for the 50/60Hz CIA timer chip. In the normal posistion, the 50/60 TICK clock, based on AC line frequency, is used as a time base. In the alternate position, the verticle sync pulse from the video section is used. The system will not operate properly without one of these clocks.

However changing the position of J200 does not seem to effect anything. Is it possible that the screens are handing out a vsync that the 2000 doesn't like?

Could it be some kind of PSU issue?

Maybe the RGB monitor has an acceptable vsync signal, but modern screens freak it out somehow so it can't fall back to the PSU method. Just guessing... would like to hear some more educated/experienced thoughts.

Then again, am I just lucky that the 500 works at all?
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Old 21 June 2019, 06:29   #2
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Sounds like your RGB to VGA adapter is not buffered (it's straight through) meaning the A2000 thinks a genlock is configured.

Easiest fix is to get a buffered VGA adapter.
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Old 21 June 2019, 06:33   #3
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Awesome, thanks!

Will report back when I get one.
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Old 21 June 2019, 09:15   #4
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Welcome to EAB.

We offer buffered Amiga RGB to VGA adaptersi as an option:

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Old 21 June 2019, 09:59   #5
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Thanks, I found you guys. This place must be a gold mine due to the huge amiga fan base
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