VNB-DB for Barco?

Back to the topic. The things seem better than I thought.

- the contrast signal should be good as it is
Driver: OK

- the brightness controll also seems easy, but I don't know what voltage range the controll signal varies in the 909.
Driver: R7-8-9 ->level shifted opamp (+invert?)

- the clamping pulse needs verification, but seems usable as it is.
Switcher: needs further verification, but promising.

- blanking seems ready to use
Driver: IC104 pin 8 -> needs only inverting (1 transistor)

- spot kill needs verification
Driver: needs only inverting (1 transistor)

- the OSD/source switch signal needs to be inverted in voltage
Switcher: IC7 pin 4,10,13 usable as it is.

- the OSD signal needs more attenuation as I saw.
Switcher: can be easily solved with the already populated HFA1100

- IBCL feedback:
Small adaptation on the VNB.

- the G2 controll circuit have to be substituted, this would be easier with abbandoning the ABL feature:
Separate board, current controlled shunt regulator: manual G2.

So the cost will be quite low, but I'd prefer a separate PCB for the G2 control. The adapter might be added to the driver board, or keep it separate in the chassis somewhere.

At this point I am leaning towards the Marquee VNB, as I think the „better for LUG tubes” thing is a bit over blown. I mean the fact that the LUGs have lower capacitance plates means no disadvantage at any rate for any design. The XG also have low capacitance guns just like the LUG, and I had no issue with installing the VNBs in it. I think this problem is more of a Marquee thing as it have a very problematic focus coil design to start with, and this may be worsened with improper G2-gain-brightness working point.
Bias in the end stage also set brightness just like the G2 voltage, but they do different for the spot size as G2 is referred also to the anode voltage. Generally the higher the G2 voltage is kept the tighter the beam will be, but high G2 voltage shuts down tube which in turn have to be compensated on the output stage biasing.

Of course the Barco end stage can also be tested, but still a lot of modifications would be needed to disable the ABL function as that is certainly not very well implemented and surely holding back some horse power. I saw that a 909 with well implemented mods on its stock board configuration can resolve 1080P 60Hz very well, I aim 1080P 72Hz or beyond.
As I said I am willing to test the 909 neckboard performance as I have the equipment to evaluate it quite faithfully, designing the measurement setup: getting all the supply voltages and support signals together on the bench which makes it painful.

These are the settings:

Normal Default Setting
Economic Lower drive current to the CRT’s, the lifetime of the CRT’s will enlarge but the light output will reduce.
Temporary Boost Higher drive current to the CRT’s, the lifetime of the CRT’s will shorten but the light output will be higher. This situation is temporary, when restarting the projector, the drive mode is automatically set to normal.
Permanent Boost Higher drive current to the CRT’s, the lifetime of the CRT’s will shorten but the light output will be higher. This setting will be saved in the EEPROM. When restarting the projector, it will start up in boost mode.

Using economy mode reduces contrast ratio because it limits maximum brightness.

The voltage is 34.5kV i think from memory, but that wont be directly affecting maximum output, the current limit setting is what affects that.

I add here some information just to see this topic is not abandoned. In fact I found solution to all problems (at least on paper) with adapting the VNB to the Barco. Also I got my hands on a considerable amount of Marquee VNBs for cheap so I could supply the whole modification myself, which would make the deal smoother and more transparent.

Also I post the manual G2 regulator circuit's schematic (one color):