Electrohome 8500 - Sepia Brown Focus? - AVS Forum
CRT Projectors > Electrohome 8500 - Sepia Brown Focus?
UncleWill's Avatar UncleWill 11:57 AM 04-10-2012
Sort of noticed this months ago but didn't really think about until I watched "RAGING BULL" in black and white. The picture was in focus, but there was a brownish, almost sepia tint. When adjusting the focus with the remote control, the brownish tint moves across the screen. I'm guessing tired parts but not sure where to start or what to adjust. Any ideas, guys?

Tim in Phoenix's Avatar Tim in Phoenix 01:25 PM 04-10-2012
Hello

The blue tube will do that; put up white field, hit "Color, 3" and vary your focus. The brown tint suggests you want to check that you are using Color Temp 6500, check that in PIC, 3. If it is set to 6500 then the gray scale may need adjusting.

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UncleWill's Avatar UncleWill 12:22 AM 04-11-2012
Thanks for the tip. No, the color was not set to 6500. Looks like I had it on some custom setup. Tried out some adjusting the RGB Focus in the Service Menu and this helped the whole picture out overall too. Will do a new GrayScale setup and rework the lenses tomorrow.
Curt Palme's Avatar Curt Palme 06:54 AM 04-11-2012
Also check your filament voltage. You might have an old LVPS that had the drifting voltage issue. Sounds like the gains of your tubes are changing, and if the filament is too high, your tubes will nuke in a few hundred hours.

Under the blue tube at the back is a two pin connector. MEasure across that connector. You should get between 6.2 and 6.5 volts. Anything higher than 6.5, and that supply needs to be repaired. I can do that, so can Tim.
UncleWill's Avatar UncleWill 09:59 AM 04-11-2012
Quote:


Also check your filament voltage. You might have an old LVPS that had the drifting voltage issue. Sounds like the gains of your tubes are changing, and if the filament is too high, your tubes will nuke in a few hundred hours.

Under the blue tube at the back is a two pin connector. MEasure across that connector. You should get between 6.2 and 6.5 volts. Anything higher than 6.5, and that supply needs to be repaired. I can do that, so can Tim.

Do you know when this issue was prevelant with the LVPS? Mine is a 2000 build. Attached is a picture of the model number. I do not have a voltage meeter with me but I'll ask one of the maintenence guys if they can help give me a reading.
LL
draganm's Avatar draganm 10:04 AM 04-11-2012
Quote:
Originally Posted by UncleWill View Post

Do you know when this issue was prevelant with the LVPS? Mine is a 2000 build. Attached is a picture of the model number. I do not have a voltage meeter with me but I'll ask one of the maintenence guys if they can help give me a reading.

ALA someone didn't put in an old LVPS you will not have the tube voltage issue.
What you do have is a P43 Phosphor issue. Your gray scale will not be perfect at certain output levels.
UncleWill's Avatar UncleWill 04:00 PM 04-11-2012
Ugh, think I heard about this. If I am correct, the P43 was specifically for the 3D simulators but has shortcomings with long term use. How come changing the focus affects the colors though? If it is a brightness issue concerning the phosphor, wouldn't the wear remain fixed in one place?
Tim in Phoenix's Avatar Tim in Phoenix 06:02 PM 04-11-2012
Quote:
Originally Posted by UncleWill View Post

Ugh, think I heard about this. If I am correct, the P43 was specifically for the 3D simulators but has shortcomings with long term use. How come changing the focus affects the colors though? If it is a brightness issue concerning the phosphor, wouldn't the wear remain fixed in one place?

Hello

It isn't wear. Blue is darkest where the focus is best; something to do with spot size. This is obvious on blue and may have a small effect on green-red.

.
UncleWill's Avatar UncleWill 12:29 AM 04-12-2012
Any recommendations on countering the effects?
Tim in Phoenix's Avatar Tim in Phoenix 07:42 AM 04-12-2012
Hello

Defocus blue a little in the service menu, UTIL, 9, 0901 and Focus


.
UncleWill's Avatar UncleWill 01:09 PM 05-19-2012
Hey, I managed to take care of the brown focus problem and was searching the forums about P43 Phosphor discussions. Found what I could about them, but have a few questions. Perhaps Curt or Tim might be able to answer:

1.) Why exactly are these not as preferred as other phosphor laden CRT projectors?
2.) What is the preferred phosphor type for home theater applications?
3.) Is it true that they give a more green picture than most other Phosphor laden CRT tubes?
4.) Is P43 more ghost prone?
draganm's Avatar draganm 12:31 PM 05-20-2012
Quote:
Originally Posted by UncleWill View Post

Hey, I managed to take care of the brown focus problem and was searching the forums about P43 Phosphor discussions. Found what I could about them, but have a few questions. Perhaps Curt or Tim might be able to answer:

1.) Why exactly are these not as preferred as other phosphor laden CRT projectors?

thay suck, light output falls if the tube stays lit, it's designed for fast on/off
Quote:
Originally Posted by UncleWill View Post

2.) What is the preferred phosphor type for home theater applications?

the perfered type is not-P43
Quote:
Originally Posted by UncleWill View Post

3.) Is it true that they give a more green picture than most other Phosphor laden CRT tubes?

more yellow actually AFAIK
Quote:
Originally Posted by UncleWill View Post

4.) Is P43 more ghost prone?

no, that's a lens, cable, or possibly ele3ctrnoics issue depending on what you mean by Ghost
draganm's Avatar draganm 12:33 PM 05-20-2012
what condition is your green in anyway, any wear? If it's not perfect then just replace with another good used tube.

I have a normal green here condition 8 with very large even wear pattern in 4:3 shape.
UncleWill's Avatar UncleWill 06:09 PM 05-20-2012
Quote:


thay suck, light output falls if the tube stays lit, it's designed for fast on/off

Haha, they suck? I'd probably have to see a comparison but I'll take your word for it seeing as you go through so many.

The second part confuses me a tad. As far as the light output falling, does this mean a very bright projected image would grow dimmer over a longer period of time?

Quote:


no, that's a lens, cable, or possibly ele3ctrnoics issue depending on what you mean by Ghost

Ghosting as in trailing of the image. Its not a problem here, just curious. THe image on my CRT direct view at home just seems quicker when responding to a 30fps video game image. Perhaps its the video processing?

Quote:


what condition is your green in anyway, any wear? If it's not perfect then just replace with another good used tube.

I have a normal green here condition 8 with very large even wear pattern in 4:3 shape.

I think we had a conversation about this before, didn't we? The wear is okay, not too bad. Needed to put the raster between the two wear lines so it would not show up. First noticed it when watching the beginning of Empire Strikes Back and then reconfigured the system to accomodate. Attached is a crude an MS-Paint picture to illustrate.

Current brightness at 20ish, contrast at 40 I think...? I'm upstate right now so I can't check it. Will be going back down to pick it up in June and learn from the DC area's CRT gurus.
LL
draganm's Avatar draganm 09:54 AM 05-22-2012
Ghosting is the image repeating itself, usually once but sometimes more times, in a shadow form. It's caused by reflections in the cabling, usually cheap cabling with high impedance.
Trailing of the image is streaking, if you have streaking then your machine needs to be serviced/re-built electronically

neonsky's Avatar neonsky 07:57 PM 05-22-2012
Good thing thats a service you provide.
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