$28 Gonbes GBS8200 Scandoubler for use with Commodore Amiga
While I probably would have preferred to order an Indivision ECS scan doubler, a really nice alternative is a Gonbes GBS8200 video converter off of ebay. I had bought version 2.0 sometime in 2010 or 2011, and could not make it work in any fashion. I think, at the time, the limitation was the ability to handle a combined horizontal and vertical (composite) sync signal at a low refresh rate ~15khz, like the Amiga puts out.
I decided to try a new version, version 4.0, from the first quarter of 2014. I bought this on ebay for $28.00 shipped which is an awesome deal. I received the board three days later in the mail, which is impressive for free shipping!
Here’s the ebay item number and description in the case where the number will change:
Genuine Gonbes GBS8200 CGA/EGA/YUV/RG
Luckily, I already had “stock” at my house of DB23F connectors, and I’m glad I bought some extra when I did. It seems there are still some sources around (in mid-2015) for some connectors, although prices seem to be going up. Worst case, you could hack an existing cable, or buy a replacement video cable off ebay, and use that.
For pinouts, you only have to connect (5) wires to get this working:
DB23 pin to VGA converter wire color
3 to RED
4 to GREEN
5 to BLUE
10 to GRAY (Composite Sync signal)
16 to BLACK (GND)
When the video converter powers up, press DOWN/AUTO button to get the unit to sync up. You may need to modify the horizontal position(I needed X position: 57) or adjust the zoom.
My unit powered up in Chinese. You need to select option 4 (bottom option) for language, and then choose English on the next menu.
I powered this with my Rigol DP832 power supply and measured the current draw at various voltages. Note that you should NOT power this thing off of the Amiga’s DB23 video port. It simply can’t support the current draw.
Current draw in idle mode(no video): +12v 133ma, +8.5v 180ma, +5v 300ma
Current Draw in active mode: +12v 200ma, +8.5v 276ma, +5v 468ma.
So if you use a +5v power supply, you need to be at least 500ma, and to be safe, I’d probably use a larger one, if available.
This blog here helped me, but remember, it’s not safe to power it off the video port!