C= A3000T no video from db15

[Tahoe]

If possible try and test a CRT VGA monitor. I have seen LOTS of LCD monitors which will not sync down to 31Khz properly. Does the monitor jump on but tell you the signal is out of sync? Then the likely cause will be it does not sync down low enough for the scandoubler to work. Only fix would be is buying an Indivision ECS or trying to source a TFT that will. Although that is becoming harder by the day!!

[Tahoe]

Strange. I've never seen this. I thought every monitor was rated to 31KHz?

In theory, Yes. I have found the problem to be related to most modern LCD's not syncing down to 31.4 Khz, usually they need a fraction higher. The 50/60hz for NTSC/PAL usually isn't a problem.
I have a bucket load of TFT's that won't run under the A3000 native scandoubler, nor older external ones. The Indivision ECS/AGA and Picasso IV work, although the Picasso out-of-the-box won't work unless you up the frequency using PicassoModeTNG.

I have found so far:
HP L1940 won't work
HP L1955 won't work
HP L1520 (oldie) works
Samsung T200 won't work
Hercules Prophet 920 works

?? All LCD's are TFT aren't they?

I meant finding one that sync down to 31.4...

[Tahoe]

Interesting...

For me it has always been the other frequency... the vertical. Most LCD panels are rated to 56Hz vertical and so don't sync to PAL refresh rates.

Interesting indeed, I think I need to look further into this, maybe I am mistaken and it is indeed the horizontal... I'll set the jumpers on my 3000T to NTSC and retry...