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**Krankshaft** · 04-09-2009, 03:05 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

What do you mean by weak picture do you mean color brightness?

Go into service mode and display the crosshatches for each color (that's what I can do on my Toshiba RPTV anyways you can turn off each color during convergence) check them one at a time is one color darker then the others?

Is the collector current on the color output transistors ok?

If this didn't happen suddenly I'd say cathode poisioning. But it sounds like a circuit problem since it happened suddenly.

**i4004** · 04-09-2009, 04:10 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

would 2 years of never being turned on damage the tubes? (of that happened)

checking the tube voltages should reveal if it's the tube...

if it looks faint and blurry, chances are it is...

**Toasty** · 04-09-2009, 04:30 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

@Krankshaft- picture is very difficult to see. You've got to bob your head around to see it. I can see the glow from the 3 tubes thru the screen. Kinda like looking at a TV in the sunlight. Maybe I'm too close to it.

@i4004 -Problem was there before it was moved. Dim picture and convergence problem appeared together. It then sat for 2 years, moved, now he wants to use it.

I don't think it truly had a convergence problem. It was likely hum not filtered by the blown cap that was causing the blurriness and colors separation.

**kc8adu** · 04-09-2009, 05:02 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

just had a zenith(hitachi) with a very dim picture that took a long time to show.
it was an open resistor to the heater supply.odd scheme with a sharp 6v regulator ic with internal switch.someone else replaced it and a bunch of stuff but skipped the resistor.supply to the reg was 2.5v.not going to get much pic from that.

**i4004** · 04-09-2009, 05:57 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

in that case, yeah, check heater voltage first, rgb voltages...then other accelerating voltages all the way up to HV etc.
(we don't have many projection tvs here so i don't know the details)

if everything checks out, and tv is still dim, it's the worn tube...
recent tubes probably can do a lot less time than old ones...

but yeah, tubes don't get worn overnight....it's a gradual process...

i wouldn't rule out the possibility customer doesn't remember that well: ie if he had dim and ok picture, and then next day he had dim and blurry picture, and said
"it was all fine untill one day"

no, it was not all fine...it was already bad, and then it become untolerable...
(just a possibility to have in mind...cutomers are not paying much attention to image properties, obviously...)

but again, now you know what to check...

**PlainBill** · 04-09-2009, 06:08 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Originally posted by Toasty

There is a whole series of steps to take in "Serviceman Mode", but I can not (will not) perform them in the customer's home. I need the set brought to the shop where I have the equipment and the ability to concentrate on it.

Do you think it is worth the effort, or should it be parked on the curb? Is there a list of "common" problems in these sets I should go searching for?

Opinions and recommendations greatly appreciated.

Toast

I'm biased. This TV is 12 years old. Even if it were possible to return it to original performance at a reasonable price it represents old technology which doesn't come close to what is presently available. If you can identify and replace another bad cap within an hour, he's got an OK set. If the tubes are bad, (worst case scenario?), how much would it cost to replace them?

I would invite the owner to take a walk through the TV section at Best Buy, Costco, or even Walmart and compare the picture (and the price tag) of a current set of comparable size. Let him make the decision.

PlainBill

**Toasty** · 04-09-2009, 07:18 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

1) He's unemployed at this time. Just lost his job. Crappy economy based termination.
2) His "other" set went tits up 2 weeks ago and he's now watching a 15" portable.
3) Tubes Are $175 each or more
4) Is not, at my counsel, going to spend a lot of money on the set.

I was hoping for a "I've seen that, go put $30 of parts in it and it will be fine" kind of answer I've seen here before.

Wishful thinking, perhaps.

**Wizard** · 04-09-2009, 07:40 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Are CRT heaters glowing nice orange? (Some of them glowed brighter).

CRT boards: Should have 200Vish for the cathodes, normally around 130V that varies with picture contents.
Measure the G2 (around 400-under 500 ish) and G1 should be held low or grounded), check all caps on the CRT boards with ESR meter. Then look at mainboard and make sure there are no solder fractures.

Before the failure, was picture excellent and nice? Sudden dim?

This tv usually have flyback pulses direct to the heaters via resistor and back through ground in the chassis. This one you cannot measure, need scope to confirm good pulses.

Cheers, Wizard

**Toasty** · 04-09-2009, 11:01 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Wizard >>Before the failure, was picture excellent and nice? Sudden dim?<<

According to him, yes.

From the feedback so far, I'm thinking this might be worth it to have him bring it to the shop. At least here I can look at it more carefully.

God that's a big sucker.

**Wizard** · 04-10-2009, 12:00 AM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Some can be pulled out of cabinet if the chassis is removeable as a unit. We call this light boxes.

Keep us updated and we'll give our feedback.

Cheers, Wizard

**Toasty** · 04-10-2009, 02:08 AM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Yup. I looked at the service manual and it seems that it can be pulled. How will I be able to view this once I get it here?

Also, I'm wondering if some screen assembly is missing? The SM says there is a Fresnel and then a lenticular....

OMG! I think it's missing a screen! When I was there I noticed the screen was a Fresnel type of screen (grooved) that was exposed to the room. I noticed because there were some "marks" on it and he said something about the kid had bumped it. Not a big mark, but I touched it lightly in the corner with a fingernail and I left a mark too. I thought to myself "that's kinda dumb, anybody bumping into it is gonna screw it up".

WTF!

He also commented that it seemed there was a gap in front of the screen as it sat in the frame. Like 1/8 inch gap between frame and screen.

ARRRGGGHHH! Is this what is wrong, it's missing the lenticular?

Toast

**Krankshaft** · 04-10-2009, 02:53 AM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Well better check out Tritronics or another major parts depot and see if it's even still available.

I bet the kid broke it didn't tell anyone and hid it

.

Whoops they are Encompass parts now ugh I liked Tritronics it seems like they joined with Vance Baldwin.

I never liked VB their prices were always higher compared to TT.

The lenticular is Panasonic part #TXFKG0597SER. Prices seem to be in the 200 range.

**Toasty** · 04-10-2009, 04:05 AM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Is that a clear or clouded or other type of plastic?

Yeah $208 and $230 depending.

Is that what is causing this?

Here comes the curb!!

**Wizard** · 04-10-2009, 12:27 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Lenticular screen is grooved and runs up and down vertically. Fensel screen is circular (on back), lenticular is on front.

Some have guard screen installed in front usually clear and set bit distrance from the lenticular screen. Guard screen is clear and not that expensive to replace. A glass store can sell you sheet of it cut to size by your measurement.

Some don't use lenticular screen, used a matte screen instead. But this does not make convergence issue.

Keep looking, you do have problem in the chassis. If pic is not bright the light output from CRT will be also dim and not so blindly bright. Working right is seriously bright.

Cheers, Wizard

**Toasty** · 04-10-2009, 01:05 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Thanks Wizard!

Specifically per the service manual, this is missing the lenticular screen. This model does not call for guard screen or matte screen.

Another question - Are the lenses supposed to be groove side out, towards viewer, or inwards towards chassis?

I am picking up the chassis tomorrow.

From my advice, that it will be over $300 by time we get done with shipping, installation, and labor just for the lens. Not even fixing the brightness issue. He's going to toss the rest of the unit and go spend his money on something newer.

The point is moot, but I'd like to find out what happened to the lens.

I do not think the convergence is an issue since that cap was replaced. I really don't think it was truly convergence as it was ripple. But, I agree there is a brightness/intensity issue. You don't need

to look at tubes. They're bright, but not as bright as I remember when looking at others. Those really hurt to look at

.

It is something I can mess with here in the shop as a learning tool.

I'll post back when I get to digging around in it. I'm sure there will be more questions...

Thanks to everyone who responded! (so far)

Toast

**Wizard** · 04-10-2009, 01:22 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

fensel and lenticular screens are taped together. With guard screen in front bit apart.

Cheers, Wizard

**Toasty** · 04-11-2009, 05:14 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

Picked up the chassis today. Double checked lens and confirmed only the Fresnel was there.

Krankshaft >>I bet the kid broke it didn't tell anyone and hid it

.<<
Spot on! He found a small piece of plastic a while ago between the screen and frame. It looked like a part of the screen, but he never gave it a second thought. He believed the problem of poor picture and fuzziness was another electronics problem. Here the set was in the kids room for a while and really wasn't in use. It's when he got it out to get ready to move that he noticed the plastic and the crappy pic.

Used tubes anyone?

Toast

**Wizard** · 04-11-2009, 05:21 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

see if yiou can fix chassis first.
Then measure the removed bezel that holds the guard window and thickness of the broken piece. Get it from glass store or something for 40-60 dollars.

You need to check 2 things that can cause convergence to come apart:

Pincushion circuit
convergence ampifier (STK ICs) and resolder chassis.

Cheers, Wiard

**Toasty** · 04-11-2009, 09:05 PM

Re: Panasonic PT-51G41V PTV Poor Convergence Weak Picture

The lenticular is missing. Apparently, that was the little broken piece he found in the frame.

It did not have the clear protective screen, ever. This model did not come from factory with it. He said he was offered that when he bought unit, but did not purchase it.

I will get around to messing with the chassis as time permits. It will be a teaching tool for Toast.

Toast

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