A1200 invisible mouse with floppy and HDD boot drops out

[PlatformerZ]

After fitting a D.K. Video Crisper RGB video buffer, which I hear is 15khz only; to the RGB port of my A1200 OS 3.9, before a Scandex doubler, I have no video signal; HDD activity stops, about when WB is loaded in startup.

I am using an external Scandex doubler to TFT monitor for both CGA and VGA modes. I tried a second Scandex and no change.

The Early boot menu shows but invisible mouse pointer. Floppy boot is the same.

From this thread: https://forum.amiga.org/index.php?topic=73237.0 I followed Oldsmobile Mikes' suggestion of swapping the ROM's for new ones and Accelerator card and PSU. Also disconnected mouse and Joystick. No Change unfortunately. 

Suggestions Welcome. TIA.

[PlatformerZ]

Further. I tested the RGB port with a meter. +5v and +12v are present plus +3v on H-sync and +.9v on V-sync. According to AI this means the F1 and F2 resistors are ok.

I tested the D.K. Products Video Crisper RGB buffer for shorts and that's all ok too.

I've made use of the time out and imaged the CF card from the A1200 with Win32 Imager to use in WinUAE. Tested the image and the CF is still good.

As far as AI can suggest, a logic error in Lisa created by current mismatch can create the symptoms mentioned in OP.