Sony KS-34XS955; discharging a CRT

[Freezer]

I recently picked up a free Sony KD-34XS955 TV. I already own the XBR equivalent of this model so I know it's a really nice TV. Even though it's a CRT TV which many feel is "old technology," it has nice features such as full 1080 resolution, digital turner, widescreen, and HDMI input.

Anyway, the problem with this TV is sometimes when you turn it on nothing happens except a blinking LED on the front. I know from searches on www.agoraquest.com that the problem is most likely the two MCZ3001D ICs on the "D" board. I've already ordered two chips and sockets. I have plenty of soldering experience so I know once the board is out I can desolder the old and solder in the new.

My question is discharging the CRT. I know these CRTs can hold a lot of charge on them and need to be discharged before you can safely work on them. From what I can tell the recommend method is as follows:

1. Attach a thick wire to an insulated flat blade screwdriver.
2. Use an alligator clip to attach the other end of the wire to a ground point.
3. Slowly work the screwdriver under the anode cup and make contact with the metal to discharge.
4. Repeat step 3 several times.

That's all well and good, but I can't find details on where to attach the alligator clip. Some people talk about a metal spring and/or wire surrounding the CRT. Also, do I need to connect the TV to ground to earth ground when performing this?

FWIW, this TV has been off and unplugged for over a week, and from what I can tell Sony Trinitron tubes self discharge in about 30 seconds. But I am not about to make any assumptions, I want to be darn sure it's safe to work on this TV.

Below are pictures of the back of the set as well as the two ICs I'm going to replace.

[PlainBill]

Don't do it that way - there is an excellent chance of damaging the CRT.

Instead, rig it up so there is a 1 megohm resistor between the screwdriver tip and the anode. This will discharge the CRT slowly. As far as a point for the grounding clip, clip it to one of the spring loaded cables across the back of the CRT.

Normally there is a very high resistance between the 2nd anode and ground, so discharging the CRT is unnecessary. Still, it IS better to be safe than sorry.

Some of the guys who work on CRT sets prefer to work without disconnecting the CRT.

Yes, a CRT is old tech, but you won't have t worry about anyone walking of with your 34" HDTV!

PlainBill

[Freezer]

Originally Posted by PlainBill

Don't do it that way - there is an excellent chance of damaging the CRT.

Instead, rig it up so there is a 1 megohm resistor between the screwdriver tip and the anode. This will discharge the CRT slowly. As far as a point for the grounding clip, clip it to one of the spring loaded cables across the back of the CRT.

Just to be clear, you're saying to clip to the area circled in the image below? As for the resistor, my thought is to solder a 1 MOhm power resistor inline in the wire between the screwdriver and the grounding point. This provides the necessary resistance but without having to rig a resistor on the end of the screwdriver.

Thanks for your help thus far. I'll report back on this project later.

[PlainBill]

Originally Posted by Freezer

Just to be clear, you're saying to clip to the area circled in the image below? As for the resistor, my thought is to solder a 1 MOhm power resistor inline in the wire between the screwdriver and the grounding point. This provides the necessary resistance but without having to rig a resistor on the end of the screwdriver.

Thanks for your help thus far. I'll report back on this project later.

I'd hook the clip to either eyelet, not to the spring. A resistor in the ground lead is ok, just make sure you have a well insulated screwdriver. There won't be enough current to kill you, but it will wake you up!!

PlainBill

[weirdlookinguy]

I have a 34XBR960 that had the exact same problem, I wrote the whole thing up here:

http://www.badcaps.net/forum/showpos...6&postcount=49

Only thing is, don't use the sockets like I did. They are no bueno in something with crazy thermal cycles like a TV. I didn't know this until Wizard pointed it out - after I did the repair.



As for discharging the tube, I think it's unnecessary and just adds risk of screwing something up to the whole operation. I didn't have to go near the anode wire or the top of the tube when I repaired mine.

[Freezer]

Originally Posted by weirdlookinguy

I have a 34XBR960 that had the exact same problem.

Only thing is, don't use the sockets like I did. They are no bueno in something with crazy thermal cycles like a TV. I didn't know this until Wizard pointed it out - after I did the repair.

As for discharging the tube, I think it's unnecessary and just adds risk of screwing something up to the whole operation. I didn't have to go near the anode wire or the top of the tube when I repaired mine.

Nice to see someone else has done the exact same repair. So the sockets are a bad idea because of the thermal changes the TV undergoes? Maybe I'll just solder the new chips in without the sockets.

You say you didn't go near the anode wire or the top of the tube. How did you get the board out without removing the anode cap? I'm all for leaving it alone, I just don't see how to remove the board without removing the anode cap. Lastly, I see you replaced more than just the sockets. Was this preventative maintenance or were those bad as well? I plan on checking ESRs once the board is removed, but as of now I wasn't expecting to replace anything except the sockets.

[Village Electronics]

Originally Posted by Freezer

I recently picked up a free Sony KD-34XS955 TV. I already own the XBR equivalent of this model so I know it's a really nice TV. Even though it's a CRT TV which many feel is "old technology," it has nice features such as full 1080 resolution, digital turner, widescreen, and HDMI input.

Anyway, the problem with this TV is sometimes when you turn it on nothing happens except a blinking LED on the front. I know from searches on www.agoraquest.com that the problem is most likely the two MCZ3001D ICs on the "D" board. I've already ordered two chips and sockets. I have plenty of soldering experience so I know once the board is out I can desolder the old and solder in the new.

My question is discharging the CRT. I know these CRTs can hold a lot of charge on them and need to be discharged before you can safely work on them. From what I can tell the recommend method is as follows:

1. Attach a thick wire to an insulated flat blade screwdriver.
2. Use an alligator clip to attach the other end of the wire to a ground point.
3. Slowly work the screwdriver under the anode cup and make contact with the metal to discharge.
4. Repeat step 3 several times.

That's all well and good, but I can't find details on where to attach the alligator clip. Some people talk about a metal spring and/or wire surrounding the CRT. Also, do I need to connect the TV to ground to earth ground when performing this?

FWIW, this TV has been off and unplugged for over a week, and from what I can tell Sony Trinitron tubes self discharge in about 30 seconds. But I am not about to make any assumptions, I want to be darn sure it's safe to work on this TV.

Below are pictures of the back of the set as well as the two ICs I'm going to replace.

Sony CRT TV does not store a charge.

[Freezer]

Success... mostly. I decided to follow the advice of "weirdlookinguy" and did not completely remove the board from the TV. I disconnected all the cables that had clips, removed the screws, and then pulled the board out as far as I could (leaving the FBT wires still connected). I propped the board up against the TV and desoldered the chips from there. Below is a picture of the board semi-outside the TV, and another close-up shot of the back of the D board.

Removing the two ICs was a piece of cake. In all the desoldering work I've done, these two ICs were the easiest to remove. I soldered in the new ICs, put the board back in, and reconnected all the wires.

Powered on the TV and it works great... for the most part. The one issue I'm seeing is the extreme upper left hand corner, the red, blue, and green images are not properly aligned. However, after the TV has been running for about 20 seconds the three color plains come into alignment and the image is perfect until the next time you turn it on. Below is an image of the issue I'm describing.

My question is, when I was working inside the TV did I bump some calibration knob/screw? If so, does anyone know what to adjust to correct this? Or is it better to just live with this problem since it corrects itself after a few seconds?

[PlainBill]

It's unlikely you caused this by bumping something.

I'd suspect a cap in the convergence circuit is a little dodgy, or POSSIBLY a bad solder joint. I'd download the service manual from Elektrotanya and look over the schematic of the dynamic convergence section.

PlainBill

[Freezer]

Originally Posted by PlainBill

It's unlikely you caused this by bumping something.

I'd suspect a cap in the convergence circuit is a little dodgy, or POSSIBLY a bad solder joint. I'd download the service manual from Elektrotanya and look over the schematic of the dynamic convergence section.

Thanks. I've downloaded the service manual and I'm looking it over now. One distinct possibility, in the service manual there is a section called "cable wire dressing" and it says if the wires are touching or near something they're not supposed to be it can cause distortion. This could easily be my problem. The service manual has diagrams, plus I have a full set of pictures inside the TV before I touched it. So I should be able to restore all the cables to their original locations.

If that doesn't work, I'll check the convergence circuit as you suggest.

[Th3_uN1Qu3]

If it only lasts 20 seconds it could simply be caused by the degauss coil... I'd leave it be.

[PlainBill]

Originally Posted by Th3_uN1Qu3

If it only lasts 20 seconds it could simply be caused by the degauss coil... I'd leave it be.

I'm slipping. I never thought of that.

PlainBill

[Th3_uN1Qu3]

If there is bad soldering or an intermittent capacitor the issue will pop up from time to time during normal viewing. If it only happens at power on and since it lasts that short... i wouldn't worry about it. If it ain't broken then don't fix it.

[PlainBill]

Originally Posted by Th3_uN1Qu3

If there is bad soldering or an intermittent capacitor the issue will pop up from time to time during normal viewing. If it only happens at power on and since it lasts that short... i wouldn't worry about it. If it ain't broken then don't fix it.

Not intermittent, but perhaps low esr, or any component changing as it warms up.

PlainBill

[Freezer]

I made sure all the wires are "dressed" properly according to the service manual. Unfortunately it didn't fix this issue. I've run this TV for hours since making the fix, the only time the problem occurs is the first 20 seconds when the TV is turned on. For now I'm going to leave it. If the problem gets worse in the future I'll worry about trying to find the problem then. For now, it's a beautiful image and a great TV.

Thanks to all for your help, and hopefully someone else will find this post useful in the future.

[weirdlookinguy]

Glad you got it fixed! I love my 34XBR960. The only place it dissapoints is that HDCP is broken on mine. If anyone knows of a cheap illegal device that would let me bypass HDCP, let me know...

I changed out the other components on mine because it is recommended that you swap all 6 components (they are sold as a kit at some places). I think that in reality you should be fine switching just the ICs.

[PlainBill]

Originally Posted by weirdlookinguy

Glad you got it fixed! I love my 34XBR960. The only place it dissapoints is that HDCP is broken on mine. If anyone knows of a cheap illegal device that would let me bypass HDCP, let me know...

I changed out the other components on mine because it is recommended that you swap all 6 components (they are sold as a kit at some places). I think that in reality you should be fine switching just the ICs.

Have you checked the service manual? HDCP seems to be a software or firmware function. I've seen instructions on loading the HDCP information on a number of TVs and monitors.

PlainBill

[tom66]

It could be that the HDCP "permit" has been revoked, or is that only for blu-ray?

[weirdlookinguy]

Originally Posted by PlainBill

Have you checked the service manual? HDCP seems to be a software or firmware function. I've seen instructions on loading the HDCP information on a number of TVs and monitors.

PlainBill

I did good sir, there is nary a mention of HDCP in there.

[PlainBill]

Originally Posted by weirdlookinguy

I did good sir, there is nary a mention of HDCP in there.

Which may mean the feature wasn't included. I just sold a plasma TV that did not support HDCP, but that had only a DVI input.

It sounds kind of kinky, but an HDCP Stripper would seem to be the solution.

PlainBill