Panasonic PT-47WX42 Convergence Issues

[tom66]

Re: Panasonic PT-47WX42 Convergence Issues

On 480i, around 15~16kHz for horizontal, 50~60Hz for vertical.
On 1080i, no idea...

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

I'll have to try that.

[f67bird]

Re: Panasonic PT-47WX42 Convergence Issues

edit: the schematic says that the +18v IS the supply for the chips... so those itty bitty voltages the SM lists must not be from ground. Now what?

Each convergence ic requires DC +18 volts on pins 5 and 10, and DC -18 volts on pins 4 and 17 measured to ground. The positive 18 volts will go thru one of the .27 ohm resistors, and the negative 18 volts will go thru the other - if they are still good. If one or more is no longer still good it will read voltage on one end and not the other.
Put your negative probe in a screw hole on the chassis and touch the positive probe to each end of each of the .27 ohm resistors that you replaced (assuming that your dmm is auto polarity) BOTH ends of one of the .27 ohm resistors will read around DC +18 volts, and BOTH ends of the other .27 ohm resistor will read around DC -18 volts when the set is powered on.

It appears the +18 and -18 are NOT supply rails at all!

Yes, they are each supply rails. They each need to have their rated DC voltage...please check again. If one or both are missing, that's a clue.
I hope that you double checked all of the resistors you changed again...you mentioned that you ran the set without the convergence wires connected, that could have taken out one or more of the resistors right away and one or both of the convergence ics right away.
Did you save both of the original convergence ics?
Oh yeah, did you solder in the convergence ics? And did you use heat sink compound? I have actually forgotten a time or two to solder them in especially if I was distracted while I was putting them in.

A few are ever so slightly browner than the others... not by a lot. They all measured up ok in circuit... should I have replaced them all anyway?

You didn't need to replace any resistors at all unless they read out of tolerance OUT of circuit.

Not being sarcastic here, but have you done any electronic repairs before?

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

First, I think you have my order of posts backwards... since the newst post quoted was the first one in your list.

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regarding the tiny voltage specs listed in the SM... I don't know what say other than that they match the Vpp's listed in the waveforms on the next page (16). Not an AC voltage, since meters read average or RMS, not Vpp. I have both voltages, the 18V had 17ish, the -18V had -19ish. The amps are rated for up to 38V. Not sure what kind of headroom they have (I'd have to check the datasheet) but those are probably close enough to not be the issue.

---

I've done many electronic repairs but none in this type of circuit.

I'm a second year EET student too.

Apart from basic amplifiers and some of the butterworth active filters, my op amp knowedge isn't that great (I can derive transfer functions and the like though).


---

I did check some things with the scope as per what I had SM charts for... and I made a video showing both what my TV does now and what I found with the scope. It's kinda crappy (the camcorder couldn't focus on the scope well, even after setting it manually) but I'll upload it to Youtube and post an unlisted link when I'ts ready.

[f67bird]

Re: Panasonic PT-47WX42 Convergence Issues

I am still not getting an answer to whether or not you saved the original convergence ics... and did you double check to verify you soldered both ics...and did you double check again that all resistors you replaced are now still good? ALL of the 2 watt resistors in the convergence circuit should be double checked now even if you replaced them.
Did you have a problem with any of the pads lifting off of the circuit board when you desoldered the convergence ics or resistors?
The fact that both convergence ics are cold is a big clue!
In my experience, from the symptoms you had when you started...you should not need a oscilloscope to fix this...just a dmm, some parts and your eyes.
Maybe it would be a help if you took a few good well lit, in focus photos of both the bottom of the board first, and then the top of the board with everything reconnected...and posted them here.

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

I am still not getting an answer to whether or not you saved the original convergence ics... and did you double check to verify you soldered both ics...and did you double check again that all resistors you replaced are now still good? ALL of the 2 watt resistors in the convergence circuit should be double checked now even if you replaced them.
Did you have a problem with any of the pads lifting off of the circuit board when you desoldered the convergence ics or resistors?
The fact that both convergence ics are cold is a big clue!
In my experience, from the symptoms you had when you started...you should not need a oscilloscope to fix this...just a dmm, some parts and your eyes.
Maybe it would be a help if you took a few good well lit, in focus photos of both the bottom of the board first, and then the top of the board with everything reconnected...and posted them here.

I have the original ICs somewhere... Although I honestly doubt they're gonna fix it (last I checked Newark didn't sell fakes).

I tried taking pics but my camera battery went out... Not sure what they would tell.

I checked and checked and checked the soldering... that seems good.

I did check awile back, and the chip was getting power on at least oen pin... I honestly didn't check very well. it's a PITA to say the least with the CRT tubes nearby (I don't want to get electrocuted).

I'' recheck for power inputs.

Youtube video of the waveforms is being uploaded.

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

Video of the actual problem (symptoms) and some things getting scope probed:

http://youtu.be/ZGrDyz3pWyI

(as of this posting, it's not fully up yet).

[f67bird]

Re: Panasonic PT-47WX42 Convergence Issues

I have the original ICs somewhere... Although I honestly doubt they're gonna fix it (last I checked Newark didn't sell fakes).

You don't see the importance of what I am asking?
The tv acted one way when you started...you changed the ics and some resistors. Now the tv is acting a totally different way. If you have checked the resistors you changed and soldering and connectors...that leaves the ics...unless you damaged something accidentally along the way.

I tried taking pics but my camera battery went out... Not sure what they would tell.

I think you are missing something in this repair, clear in focus photos might show something that more experienced eyes could notice.
My thinking is that if you check everything else and it all checks good, then put both the original ics back in and see if it brings you back to where you started from.

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

I still doubt it's the ICs. It wasn't working before... it was different, but it wasn't working. I think something is causing my new chips to do nothing and the old ones to act odd.

The ld IC's are a bit mangled anyway... the desolder didn't go very well on one pin and it tood some work to get it out.

I'll get some pics... it isn't the prettiest job but AFAIK all is in correctly.

Q: is this main board more than 2 layer (i.e. more traces than just the top and bottom)?

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

Youtube link was a fail... I thought they did away with the 10min rule... f**kers.

In the mean time, I took a few pics. They're attached for now, I'll edit in any commentary I see necessary.

[tom66]

Re: Panasonic PT-47WX42 Convergence Issues

Minor critique: Your soldering here could do with improvement. You want it look like a small volcano not a bubble on your lead. This is just for long term reliability. Do not heat and melt the solder onto the iron then put it on the lead, it leads to cold joints like in the picture.

Flux cleaner would be a good idea, some of that stuff is conductive!

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

Minor critique: Your soldering here could do with improvement. You want it look like a small volcano not a bubble on your lead. This is just for long term reliability. Do not heat and melt the solder onto the iron then put it on the lead, it leads to cold joints like in the picture.

Flux cleaner would be a good idea, some of that stuff is conductive!

Buddy, Mysoldering DOES look like volanoes... I do know how to solder!

See this video I made awhile back... yeah, I was a little heavy on the solder, but look how old that video is... I've had mauch more practice since and I know my soldering is better than that.

I'll get a better shot later to show what I mean.

And that flux is no clean... Most is from the desoldering braid, some from my solder. This isn't a glamor contest so I don't care (plus it helps if I ever need to desolder again).

[tom66]

Re: Panasonic PT-47WX42 Convergence Issues

What about R7002? It has a clear bulb. R7004 looks a little iffy, but I can't tell.

I know you can solder...! Your soldering technique looks fine. I prefer to heat a little further along the lead if I've got a more powerful iron as it leads to very easy and reliable joints, but your method is fine. Most of the joints are fine, it's just you should clean them up in case it's the problem, or for reliability anyway.

No problem about the flux then.

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

What about R7002? It has a clear bulb. R7004 looks a little iffy, but I can't tell.

I know you can solder...! Your soldering technique looks fine. I prefer to heat a little further along the lead if I've got a more powerful iron as it leads to very easy and reliable joints, but your method is fine. Most of the joints are fine, it's just you should clean them up in case it's the problem, or for reliability anyway.

No problem about the flux then.

That video was shot back when I only had 30W... I now have 60W.

I checked already, yeah, that joint is a bit bubbly, but I checked and it was well bonded to the pad.

[ben7]

Re: Panasonic PT-47WX42 Convergence Issues

There appears to be a current sensing circuit for STK each amp chip.

In the circuit on page 78, it shows that there is a +18 and -18 power input. The 0.27 ohm resistors are probably for the current sensing. Then, there is a 'CONV +18v' and a 'CONV -18v' bus. Those are current sensed. What are the CONV rail voltages at, compared to the main 18v rail input?

Sorry if you guys went over this already.

[tom66]

Re: Panasonic PT-47WX42 Convergence Issues

It is a good point; perhaps there are transistors to switch off the rails due to excessive current?

[f67bird]

Re: Panasonic PT-47WX42 Convergence Issues

The board and soldering look good to me.
If the stk ics have the +18 volts at pins 5 and 10 of each ic, and -18 volts at
pins 4 and 17 measured to ground... then I'm thinking along the lines of the convergence being muted or disabled. In some sets that can be done in the convergence setup.
The service manual shows on page 42 a convergence mute setting... please double check that. Also please take a look at the format aspect switching note at the bottom of page 42.
Also look at page 15 A-board check points. There is a row of 6 jumpers in a row near the 2 watt resistors where you can check the convergence ics output voltages. They are labeled BV, BH, GV, GH, RV, RH.
Please check the voltage of each jumper to ground. Not sure why the convergence -18 and +18 volt checkpoints are showing a less that one volt reading though...I think that's a mistake. what do yours measure?
Did you check both of the ORIGINAL .27 ohm resistors out of the circuit? Were either of them out of tolerance? There is an SOS circuit (transistors 7060 and 7061) associated with the .27 ohm resistors R7060 and R7066.
One more question...is the picture and sound working (other than the convergence being messed up)?

[ratdude747]

Re: Panasonic PT-47WX42 Convergence Issues

Picture and sound works great.

I'll have to wait on service mode until I have more AAA's to use a better universal remote... I was using the cable co's remote but for channel adjustments its useless (when you hit a number, it defaults back to cable box mode). Once I get some AAA's tonight I have a logitech harmony I can dig out and program to work with it. Until then, I can't go to any cable channel other then 4 (since 124 would require a manual entry).

(yeah, I was never given a remote to use with it)

Tonight I'll also try again with the video... in two parts.

btw, the .27 resistors were checked out of circuit, I'm not sure if they are good (I don't have 4 wire / two meter access at home and thus no <1 ohm precision to speak of). I at first thought they were bad and replaced them.. but I forgot to account for the resistance of my alligator leads. After subtracting the measurement of a short (clip to clip), I came up with a 0.2ish result... so I guess they are good? I re-installed them since they carry substantial current and my replacements looked to only be 50% of the required wattage (1W resistors my a**).

[Mr Bill]

Re: Panasonic PT-47WX42 Convergence Issues

Did you label the 2 connectors i put a square around? When i replaced the convergence chips on a 50" toshiba i forgot to label them. When i first turned on the tv it was bad blurry and you couldn't adjust it at all. I had the connectors that i put a square around in the wrong locations. It looks like the 2 connectors are about the same number of pins and within a reasonable distance they could get switched.

[f67bird]

Re: Panasonic PT-47WX42 Convergence Issues

Another possibility I thought of is to check the 4 white connectors that connect the deflection board and signal boards. Sometimes they develop bad solder joints
especially on the outside pins. I've seen that on lots of different brands of big screen tvs. You would need to check the connections on both boards.
The original .27 ohm resistors are most likely good if they each measure around .2 ohms with your meter. Even if your meter is slightly off, if one was bad they wouldn't both read identically.