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GAK! Projector's fine, but the direct-view CRT set is on the fritz! (with pictures)

869 Views 26 Replies 8 Participants Last post by kal, Apr 16, 2003

kal

Discussion Starter · Oct 14, 2001

Wouldn't you know it: the 23K hour circa 1990 BarcoGraphics 800 is running fine, but my 32" Hitachi Ultravision 32UX8B is having jealous fits as we spend most of our time now watching the 110" screen in the basement...

Over the last few weeks, whenever the 32" direct-view set is turned on all we see is green lines - what looks like the raster (fine horiz lines, and brighter sweeping lines slightly tiltled). Sound is fine, and if you look closely, you can see the regular TV channel image behind the green lines. I've taken a few screen shots below.

The solution has been to turn the thing off, wait 10 seconds, then turn it back on and all is (usually) ok. It never fixes itself automatically - always needs a power cycle. Lately, it requires more and more cycles before everything comes back normally. Seems as if something needs to warm up properly before it comes on ok.

Any techs see this sort of thing before? Any idea what I should pin-point? Thanks guys!

Kal

http://www3.sympatico.ca/kwallner/IM001060.JPG

http://www3.sympatico.ca/kwallner/IM001067.JPG

(the black band is not visible - it's because of the 60Hz refesh & camera shutter speed).

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1 - 20 of 27 Posts

Jay Wilson

· #2 · Oct 14, 2001

That looks like 1 of 2 things. Eihter good or bad. Those appear to be kine bias lines, si it could be in this circuit. The bad news (and more likely) is that it is an internal short in the neck of the picture tube. Some shops will try to "burn" the short out. What we do is apply much higher than normal voltages to the tube. Either the short will be gone you can get a little more life out of the tube, or you ruin it completely. If we do this in our shop, there is no guarantee and they may not even have the ability to cylce on and off as you currently do.

What I would say, is weigh the differences...if you're ok with cycling it on/off...then don't do anything. If you hate doing this, and can live with the possibility that the set may get permanently damaged, have a reputable shop try the above. Of course I'm saying this assuming the worst, they may get it in and find the circuit is bad rather than the tube. In any case, good luck and keep watching the 110" screen!

kal

Discussion Starter · #3 · Oct 14, 2001

Thanks for the info Jay!

I'm confused about a few things that you wrote:

Those appear to be kine bias lines, si it could be in this circuit.

What's kine? Did you mean line? Is this the equivalent of G2 (tube bias) found in FPTV's?

I wish that cycling the power on/off was a solution, but it seems that it's getting worse: Used to be that one cycle was enough, but today it took 10-15 mins of cycling (and waiting in between). I figured whatever was causing the problems finally got pushed over the edge.

I don't have a service manual for this thing (but do have most of the tools needed), nor the expertise of most techs so I doubt this is something I could fix myself. I was just curious if this problem is immediately obvious to any of the techs.

Thanks again,

Kal

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Jay Wilson

· #4 · Oct 14, 2001

No, it is kine (pronounced kinney) bias lines. Yes they are similar to the G2 fo FPTV. Normally you can get the lines by adjusting to the max the IHVT (flyback xformer). However, when it goes out suddenly, and the cycling power sometimes cures it...that's what makes me think it is more serious. What's the model number and I'll look for a schematic at the office next week. Would be glad to loan it as long as you promise to send it back. Let me know and I'll see what I can do.

kal

Discussion Starter · #5 · Oct 14, 2001

Jay,

Thanks for the generous offer - though I don't want you to go to any hassles - I'm not sure how much I could do with a schematic (as it would probably not give reference voltages/waveforms to measure right?).

Anyway, here's the info:

Brand: Hitachi

Model: Ultravision 32UX8B

Serial Number: V6F004797

Manufacture date: June 1996

However, when it goes out suddenly, and the cycling power sometimes cures it...that's what makes me think it is more serious.

Actually, it never goes out suddenly when the unit's already on and working. I only get the problem at power-up, and only when the unit has been off for many hours.

I also noticed today that once the unit's on and working properly, during very dark scenes I can still [slighty] see the brighter sweeping lines (the kine bias lines?). As you mentioned, you can get the lines by adjusting to the max the IHVT (flyback xformer). Maybe things have drifted slightly and need re-adjustment, or possibly a part has gone flakey.

Kal

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Curt Palme

· #6 · Oct 14, 2001

Try tapping the neck of the green tube. Not too hard, and use something like the handle end of a screwdriver. If it's a short, you'll probably see the tube flickering.

Otherwise try swapping CRT sockets. Usually the video oputput stage is located right on the neck of the tube, and see if the problem switches to another tube.

CURT

kal

Discussion Starter · #7 · Oct 14, 2001

Curt,

This is a 32" direct-view set with one tube, so there's only one CRT socket! So while the video output stages are probably split into RGB, swapping one for another probably requires some re-wiring no?

Kal

Jay Wilson

· #8 · Oct 14, 2001

Actualy Kal, IF I have the manual, it should have all the voltages, scope diagrams, etc. We sold Hitachi until about '96 or '97, and I are still an authorized service center. I'll look into and see what I have.

As far as all of the sudden, I didn't mean that it went out while watching, I meant that it had gone out on its own (without any help if you know what I mean

) It seemed more of a part failure rather than a mis-adjustment. That's all I meant. I will let you know about the manual next week.

BTW, you may try Curt's suggestion also...tap lightly (don't break the end of the tube off...then you're screwed) but if you can make the lines come and go, then it is definately a tube short.

Good luck

Jay Wilson

· #9 · Oct 30, 2001

Kal, Boy has it been a bad 2 weeks. My technician turned in his 2-weeks notice for medical leave, so I had to back burner looking for the manual. I did look today, and unfortunately I don't have that one...at least it's not where its supposed to be. As I celan the back area to make ready for a new tech, I will keep my eyes open for Hitachi manuals and hopefully try & fix you up.

kal

Discussion Starter · #10 · Oct 30, 2001

No problem Jay! Thanks for looking.

Oddly enough it seems to have stabilized a bit - now it happens about 50% of the time when it's powered up but a couple of power cycles always seems to fix it.

The only new thing is that it has started to do it in red from time to time now (not only green).

Kal

kal

Discussion Starter · #11 · Jan 12, 2002

A new development: While the TV works more or less normally after you cycle the power a few times, you now see the bright green tilted lines (from the images above) more predominantly over the regular TV image. It's starting to get distracting!

Does the fact that the green slanted lines are brighter now and that it sometimes come up red bring any new information or possibilities to the equation?

Curt: Still have to take the back off and start tapping.... that's my next step.

Kal

MikeEby

· #12 · Jan 12, 2002

Kal,

I am sorry to say I thing I agree with Curt. In a past life I was at TV technician and it does look like a shorted gun in "THE" CRT. I think what Curt was referring to was to swap the output transistors on the board attached to the neck of the CRT and see of the problem changes to another color. It also just could be a cold solder joint on that board. Take the back off and lightly tap around that board to see of anything changes. It is a very crude trouble shooting method, but it seemed to work.

Good Luck

Mike

kal

Discussion Starter · #13 · Jan 12, 2002

Thanks Mike! I don't think it's a bad output transistor on the green as it happens about 70% on green and 30% on red.... so both output transistors have gone bad all of sudden? Unlikely.

I'll take the back off, and start tapping and check for cold solder joints (or simply resolder anyway just to be safe ... I did this for all the heavier items on my BG 800 cards when I first got it even though Curt always does this himself...

).

Kal

kal

Discussion Starter · #14 · Apr 14, 2003

Just to put some closure to this old thread:

Jay, Curt, Mike: You were all right on the money: There's definitely a short in the CRT neck of this 32" direct view TV.

A little tap to the neck is all that is needed to get the TV to switch between "normal", "all green", or "all red".

Problem is that it's needing this "tapping" more or more often. It was fine for almost 8 months, but now it's starting up again I'm starting to get sick of it! ... time to look for a new TV.

Kal

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Tinman

· #15 · Apr 14, 2003

I had this problem with a lot of JVC tubes.

Here's how I got it fixed: At this point the tube is shot anyway, so there is nothing to loose. I do own a sencore tube analyzer, but popping the tube did not help. The solution was to increase the filament voltage and let it cook a bit. I cycled the filament several times like this. Eventually the greater expansion and contraction caused the short to disappear. It was a real longshot... but this worked on 10 out of 12 sets I had with the same problem.

Marc

BarryFish

· #16 · Apr 14, 2003

Sometimes small flakes of oxide get between the cathode and the heater.

Being metallic oxide, the nature of their contact is inconsistant.

When they short the cathode is grounded, which turns the gun full on. With the gun full on, there is no retrace blanking, which is why you get the bright raster and super bright diagnoal lines.

Try putting the CRT on it's face then tapping, that way, you might be able to clear the fault out of the gun. (gravity assist) Power on (or on-off to take advantage of the thermal movement) when tapping might help too.

Seems funny though that you have the problem with two colors. That would tend to indicate that it is something in common - like a video output or decoder chip.

Did you try tapping anywhere else (like the neck board or decoder section of the MB) ?

Regards,

Barry

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kal

Discussion Starter · #17 · Apr 14, 2003

Hi Barry! Thanks for the additional advice!

I did try tapping around other places as well. Tapping the neckboard (board socketed to the CRT) didn't do anything unless tapped the edge hard enough to 'shock' the CRT neck itself. Tapping the CRT neck itself required considerably less force to make the problem appear/disappear.

I'll try the gravity assist idea... that's a good one - never thought of that.

Thanks!

Kal

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kal

Discussion Starter · #18 · Apr 14, 2003

Marc: Not sure I'd know how to increase the filament voltage on this thing... I don't have a service manual to see where the filament voltage could be adjusted. Didn't notice anything with an obvious label in the P/S either.

Kal

spearce

· #19 · Apr 14, 2003

Kal, you have a lot more patience than I do. I never would have let this go on for 2 years.

Ditch the 32" and stick with 110" FP.

kal

Discussion Starter · #20 · Apr 14, 2003

I don't really watch the thing much... it's in the family room. My wife's about the only one that spends any amount of time in front of it. Though it was fine for over a year and now has started to act up again...

Kal

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