CurtPalme.com Home Theater Forum

Elmar · Joined: 26 Jan 2008 Posts: 11 Location: Munich, Germany

Hello.

I have a problem with my BG1208. In 90% of all szenes the set up of the CRT is fine, colors are pretty balanced and natural.

But in very bright szenes filling the whole screen (i.e. major part of the picture is close to 100% white - e.g. white wall, cloudy sky...) I face a problem with the blue tube. It's light output is too low, the picture is yellow / brownish. If the white area is smaller and is not filling the whole picture the color is fine again. Defocussing blue did not really help.

For me it seems, that a current limiting circuit limits the maximum beam current for the blue tube in case of a screen-filling bright picture with a high blue portion.

Is such a "beam current limiting curcuit" existing - and if yes (how) can I adjust it myself?

Some words to the set itself - maybe it helps:

Originally it has been modified by SEOS, for curved screen, I think. This modification has been reversed before the previous owner bought the projector. Wenn he got the set, the tubes where broken (glass physically damaged). So he organized a set of P16LNQ tubes and installed them, before he sold the CRT to me. The tubes have a snowwhite surface and do not show any burn. However - I do not know where he got them and if they are original or have been refurbished ect.

**Curt Palme** · Posted: Sat Jan 26, 2008 5:44 pm Post subject:

Swap the neck boards over between the blue and green tubes. I've had a weak neck board cause exactly what you are seeing.

Elmar · Joined: 26 Jan 2008 Posts: 11 Location: Munich, Germany

Thanks for the extremly fast reply.

I am not experienced with the hardware. Are the neck boards in a box? To to be sure to swap the right thing I made a photo (attached).

n@t · Joined: 02 Apr 2006 Posts: 63

Elmar · Joined: 26 Jan 2008 Posts: 11 Location: Munich, Germany

Hi Bernd.

Nice to see you. I think I need some guidance for the swap. May I call you? Is +49 ..... 893 still valid or Skype?

Elmar · Joined: 26 Jan 2008 Posts: 11 Location: Munich, Germany

OK.

The good news is that I managed to swap the neck boards B <> G on my own - and the set is still working (I am very anxious about everything which is directly related to the tubes, high voltage, glass... - however, it was not a big thing swapping them).

I do not see any improvement yet, blue is weak also in the lower IREs now. In a black picture I can not see any raster glowing on the blue CRT. Phosphor is completely dark. So I guess I need to re-adjust some things, at least G2.

It is years ago since I have set up the projector and did not touch it since then - so I am not 100% sure anymore where to adjust G2 (my 1208 does not have G2 setting in the OSD menu).

Are the potentiometers in the picture the ones to control G2?

n@t · Joined: 02 Apr 2006 Posts: 63

Hi,

yes the Potentiometers ones to control G2!
You have PM.

Regards,
Bernd

Elmar · Joined: 26 Jan 2008 Posts: 11 Location: Munich, Germany

Thanks. In the meantime I re-adjusted G2 and the color balance quick&dirty, I am pretty satisfied with the result.

Just one thing confuses me: If the problem is the neck board, I expected a similair problem as stated in my first posting with green instead of blue after the swap -> I expected bright white szenes to have a magenta colour fault. This did not happen. Maybe the new G2 settings supress the effect.

However, my problem is solved now, thanks Curt, thanks Bernd.