Emerson 609 projection TV

[Phil Nelson]

Ding-ding-ding! old_coot88 was on the mark, as usual. Broken lead between C6 and junction of M3/M4 in the Sams schematic, so no juice coming down that line.

Simple to diagnose (once you know where to look), and a big fat pain to fix. It will take 1/2 hour of horsing around to get all the heavy chassis out of the cabinet and back into the workbench, and about 1/2 minute to repair the break!

While it's on the bench, I'll be able to view the CRT face and judge the focus there.

Later,

Phil Nelson

[Electronic M]

If face focus is good, look into optical focus. There may be mechanical adjustments for it.

[Phil Nelson]

Yes, there are several mechanical adjustments, as the Rider manual shows in detail.

I temporarily reconnected the broken wire with a clip lead, which brought back the power supply and full deflection. Now I'm back where I was before, with lousy focus. This is the best I can get using the two electronic focus controls:



The focus on the CRT face looks good to my eye, so I'm guessing that one or both of the reinstalled mirrors is cockeyed. I didn't mess with any of the mechanical adjusters before, such as the tilt adjusters on the base of the box. It's possible that some adjuster was seriously screwed up long ago, but the image that I got before resilvering the mirror was much closer to focus (and correct screen geometry) than this. Maybe I'll spot something obvious after I open the optical box back up.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[old_coot88]

This is a dumb question, but does the resilvered mirror have a protective film that needs to be peeled off?

The reason for asking is, I got skunked that way once with a new camera that was blurry til I figgered out what was causing it.

[jr_tech]

Is the mirror adjusted to be exactly 45 degrees to the optical axis?

jr

[Zenith6S321]

Originally Posted by Electronic M

If face focus is good, look into optical focus. There may be mechanical adjustments for it.

I agree, that with good focus on the CRT, the poor focus on the screen must be due to a miss-alignment in the optical path.

I have not worked on your projection TV model, but I have adjusted Barco projectors that have a Scheimpflug lens mount that allows you to adjust left-right and top-bottom optical focus. If you can tilt either the CRT face, the projection screen, or possibly the lens plane you may be able to correct the problem. See if you can find any mechanical adjustments that will let you tilt one optical element with respect to the others. I suggest you try to get good focus at the center of the image and then tilt the CRT, lens, or projection screen to adjust left-right and then top-bottom focus.

Dave

[Phil Nelson]

There wasn't any protective film on the resilvered mirror.

I didn't measure the angle of the plane mirror, so that's worth checking. There is very little range of movement for that mirror, once you have adjusted it so that the CRT is centered and clears the hole. There's a bit of elbow room, however. There are no adjusters for the spherical mirror, which is bolted perpendicularly inside the front wall of the box.

The manuals say nothing about installing or adjusting these mirrors, which was outside the scope of ordinary service, I guess. They must have used special jigs in the factory for this task. Due to X-rays, you can't loosen the mirrors and fiddle with them to watch the effect while the TV is playing, so the process might be tedious:

-- Make a little adjustment.
-- Close up box.
-- Turn on TV and view the screen.
-- Turn off TV and open the box.
-- Repeat as needed.

The manual does describe a bunch of adjusters for the optical system, including one on the corrector lens, but I don't want to mess with those until I confirm that the internal mirrors are installed as well as I can manage.

Phil Nelson

[old_tv_nut]

I think the optics should work in the reverse direction, so it would be possible to put a printed test pattern in place of the screen, illuminate it brightly, and observe the image on the tube. But probably not worth going there if there is little adjustment available.

I think I would continue to verify the internal mirrors are installed correctly and then move on to the described adjusters, as you say.

[jr_tech]

Or, perhaps shine a laser pointer on the center of the screen and see if it is visible in the center of the 3np4.

jr

[Phil Nelson]

I pulled the chassis and opened the optical box. I thought that the spherical mirror could only be mounted in one way, bolting onto the rear wall of the box. While it doesn't have adjusters as such, now I see that the holes in the box are bigger than its mounting screws, providing some wiggle room:



Large washers go on both sides of the hole, so clearly some sliding back & forth was contemplated.

With all three screws loosened, you can slide the mirror a bit in any direction. Not foreseeing that alignment would be an issue, I have no record of exactly how it was mounted before I removed the mirrors. Nor do I know exactly where it was mounted when it produced the most recent picture, since I didn't know the screws had any leeway until I had loosened them all today.

I don't have a factory jig for aligning all this stuff, so unless someone has a better idea, I'll mark the box with tape tags showing the center of each mounting hole, and try to remount the mirror dead center in all three holes.

Also on my to-do list is checking the angle of the plane mirror to make sure it's exactly 45 degrees, and to ensure that each of the three side clamps is holding it the same distance from the struts (i.e., even if it's lying back exactly 45 degrees, it's not tilting sideways, either).

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[jr_tech]

You need one of these!

http://www.earlytelevision.org/philips_test.html

Perhaps something similar could be fabricated.

jr

[Phil Nelson]

Wow, that Philips gizmo is clever. It sure would simplify the optical adjustment process, although fabricating one goes far beyond my pay grade.

Meanwhile, I reopened the optical box today. After much fussing & cussing, I readjusted the spherical and 45-degree plane mirrors. Now, the picture is similar to what it was before I pulled those mirrors for resilvering:



I haven't yet done ANY of the multiple mechanical adjustments, so the picture is blurry and the screen geometry isn't perfect. Presumably things can be improved somewhat that way.

It also looks a little bloomy on high-contrast content, as you can see in the animated .GIF. Poor HV regulation? There's no quick/easy way to measure the HV output, as you would in a conventional TV, so this is only a guess.

Speaking of mirrors, I stuck my head up inside the pop-up canopy to inspect the big (final) mirror. Guess what -- it looks bad, similar to the degraded surface on the 45-degree plane mirror. That would explain some of the image weirdness seen in the last photo, which is more than just being out of focus.

Tomorrow . . . .

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[old_tv_nut]

Hard to believe the optics could do all that. Maybe some combo of scan and optics, but I really think scan is most likely the cause of it all.

With all that distortion at 6 o'clock and 9 o'clock, you'd think the range of 7-8 o'clock would be worse yet if it were optics.

[Electronic M]

I t should be fine.... If you're still worried and have one of those TV magnifier accessories for 10/12" sets place it in front of the CRT and stand back a few feet...X Ray's are exponentially attenuated by air. Even if the CRT were a strong emitter once you get about 4 ft away the dose should be well within safe limits.

Another worry wart option would be to grab the leadded safety glass off of a color set and place it between the CRT and you.

[old_tv_nut]

25kv is starting to produce X-rays, and unlike color CRTs, that one most likely does not contain enough lead or thickness to reduce them. As said above, standing back several feet should be good enough protection. Also, X-ray effects are cumulative, so if you just have a quick look to see the shape of the circle, no problem. As an additional measure, you can turn down the brightness and run at much lower beam current for direct viewing.