You might have an intermittent connection problem on the main board.
Have you tried reseating the KS ROM chip?
Which ROM version are you using? Anything else connected on the main board? Floppy disk drive connected still?
Are you using a HDD drive on the IDE header?

The Indivision works fine as long as you don't mess around with the configurations too much. The output is DVI.

Worth a look

https://www.amigalove.com/viewtopic.php?t=324

Hey there!
I am new to the Amiga Universe and about to purchase an A1200.
Since I am also doing youtube videos I am trying to get the best possible footage.

But after looking into the options for the A1200 this seems to be more complicated than I initially thought.

I am using a Retrotink4k and for PC I take the original signal and scale it pixel perfectly. For simplicity I will mention the 640x480 signal which I scale to 1280x960. It's important to me that it's not scaled to 1080p for example. For a resolution of 320x200 I rather scale it to 1280x1000 to come closer to aspect ratio correctness while keeping it pixel perfect.

So I am very much focusing on the best possible signal. Just having it "displayed somehow on a modern screen" is not what I am aiming for. In fact the original signal doesn't need to be displayable at all as long as it can be converted perfectly.

So I have been looking into options for the amiga 1200. Generally from what I can see, excluding the RF and Composit options, there are basically 3 options: getting the signal from the original video port, getting the signal from a turbo card, or getting the signal from an additional graphics "device" or mod.

Original Video Port:
Generally I'd need to either put it into the tink via VGA or the SCART Plug but I guess VGA would make more sense.
Amigastore offeres an "Amiga RGB to VGA Monitor Adapter" for just 17€
But when asking around someone mentioned to get the Adapter for 49€ from Axel81l (ebay) instead, as normal adapters would show a vertical line, even on the retotink4k.
But then again, I have read on the english amigaboard that people were not impressed and the line removal would come of the cost of sharpness. Others on amibay report that the bars are not completely removed.
But most of this is also aimed on display on an LCD which personally I don't care about as long as the signal can be used well in the retrotink 4k. But I have absolutely no idea on how to interprete that mixed bag of reactions.
Also I have seen that there a multiple versions by Axel81l of adapters, also without that line remover. Some buffered, some unbuffered. Does it actually make sense to have something buffered on the amiga 1200? Or should I go for an simple unbuffered vga converter?

Turbo Card:
Generally I'd like to keep the amiga rather "minimal" without much of an upgrade in terms of capabilities or adding a raspberry pi. The current plan is to just have an ACA1211 for faster RAM/ better WHDLoad functionality.
Afaik there are turbo cards which do offer HDMI options but I don't know if they have prescaling or similar. If you have strong opinions here you might share them, but this is mostly a solution I am not looking into as I'd like to keep using the "original hardware" as much as its feasable.

Additional Graphics Device/Mod:
What I mean with this is something like a RGB to HDMI mod which seems to not exist for the A1200. Or the Device from indivision, which apparently comes with problems depending on resolution, internal scaling and also 50 HZ not working perfectly. There is also the ScanPlus AGA. But doesnt seem available anymore and I also don't know if it would do much an external tool wouldn't also do.

So what is your suggestion here? Obviously besides of going emulation or fpga.
As mentioned I got a retrotink4k. But for the Retrotink4k to have a near perfect scaled output, it would need to get a near perfect unscaled input. Which can be 50Hz, and also be any odd resolution. But it got to be clean.

Thank you for your input!

To update, I have moved to porting E-UAE Wip4. Got the source to a compiling state. Flattened it all down to one makefile.

Started debugging, it booted to title and version number. Using PSPLink, makes life so much easier. Found it was crashing at joystick init. Fixed that, got further, it now loads kickstart, then dies when CPU kicks in, NULL at pointer. Will keep at it.

Aim is to have an untouched uae core and only mess with psp backend. Obviously, uae core will need to be altered in places, but want to get it booting as clean as possible.

PSPLink, is great, however it takes up part of the heap memory. So you can run it once, then every attempt after that, gives you exhausted memory issues. Spent 2 hours chasing RAM issues, until I realised some of the RAM is taken by PSPLink.

Its all learning, but fun.