CurtPalme.com Home Theater Forum

[BruceR]

I've just set up a brand new out of the box, zero hours 1292 to replace my G70 as I've finally run out of good B input boards. I left the factory settings for focus and color temps. as they were at first. After using it for about a week, I noticed a slight red cast to the background in dark areas. I muted the pic. and noticed the red tube was the only one not completely cut off, glowing moderately I'd say. I found it didn't respond to the bias or gain controls, but the values counted up and down on the screen, the other tubes did respond. I found a thread on another forum that talked about an 'AKB link', a small plug with a wire link on the CFB board. They talked about whether that link should be in or out. My new projector doesn't have the plug/link fitted, it's just not there, but my parts projector with about 8,000 hours on the clock does have the link, so it's been there for the whole 8,000 hours. One member mentioned that without the link, one of his tubes, (he couldn't remember which one), wouldn't adjust, like mine. With the link, it would adjust, but the pic. then had a lack of contrast, and looked washed out, which is exactly what I found. I removed the link again, selected one of the color temps. I'll never use, muted the pic. and set about matching the glow on the other two tubes to match the red, looking into the lenses and using the bias controls, then adjusted the gain for a white square. After playing with the bias settings some more, I've now got an excellent pic. BUT none of the tubes now cut off completely, which doesn't seem right. Anyone got any ideas? Thanks in advance.

[gjaky]

If you see some glow only by looking into the lens, I think that can be OK. Obviously you'd need a color calibrator for proper results. But off hand usually, if the tubes completely dark even if you look directly into the lens you most likely crushing the blacks.

[BruceR]

I've played around with the bias and gain controls some more, and I've settled on having all the tubes just above cut off with no signal, just slightly lit, with the AKB link fitted, pic. is excellent. I now know that AKB means Auto Cathode Bias, or Auto Kine Bias. With the link removed, which is supposed to be the default position, the red remains quite a bit brighter than this, and can't be changed. So I'm thinking this might be some kind of a reference setting, but what I don't get, is how having the link out can be the default position because of the preset minimum brightness of the red tube. On another note, even being a brand new projector, the rear remote sensor failed after about a week, and I had to grab the one from the parts unit. Anyway, thanks for your input. I did take a pic. of the screen after I had finished, if I knew how to post it I would.

[gjaky]

Keep in mind that the projector might have low running hours, still it is 30+ years old. These CRT projectors were pushing the boundaries what was possible electonically, also very complex construction, so it is not impossible that it got broke to some extent even just sitting around.

[BruceR]

Thanks, I took that into account before I took the leap of installing it on the ceiling in place of my G70. Considering I inherited it, a parts unit, and an as new G90 with a new Dallas chip, but unfortunately with that other faulty chip made from unobtanium, all for free, I decided to give it a try. Apart from that minor hiccup, it seems to be working quite nicely now. I'd say slightly sharper than the G70, not as bright, but adequate. Fan noise doesn't seem to be a problem, a bit noisier, but not drastically so, just turned the amp. up a notch.

[gjaky]

Great! Although I have never seen a 1292 in person, but based on what I've gathered over the years about the 1292 raised great appreciation towards them.