[vtech]

.....like I mentioned at this point, I am not sure if you have a degauser problem or not? Without seeing it & knowing exactly what you have and what happened, it is only assumption.

Rather than investing in tools that may or may not solve the problem, suggest getting a TV tech or ask someone who has some experience.

To answer your questions... yes, magnetizing the tube can affect the entire screen.

It is very unlikely that the cable box's txformer can magnetize the tube. The idea was that if the box physically hit & moved the magnet rings on the back of the tube, the colors would go off.

[tvwatcher]

Last three questions before I go buy a degausser coil (I promise), in my case the colors are off over the entire screen, not just in one area. Is this typical for the colors to be off over the entire screen when the shadow mask becomes magnetized?

I mentioned earlier my Mom had the cable box sitting on top the TV which I'm sure contains some kind of step down tranformer. Is the magnetic field from a small transformer enough to magnetize the shadow mask entirely?

Also, remember the cable box slid off the TV when I pulled out the VCR and struck the outer case somewhere on the back of the TV before falling to the floor. The cable box could have been on or even if it wasn't there is still power to the circuit so you can power it on from the remote so which means there would still be power to the transformer. Could the cable box when it fell passing over the purity magnets separted only a small distance by the casing, somehow chaged their magnetic properties where now they need to be adjusted?

Thanks again for the help. As you can tell, I'm seaching for the root cause which I'm hopeful will lead to the correct diagnosis the first time. Plus, I would really like to know so I can prevent it from ever happening again.

[vtech]

[tvwatcher]

What about a static electric discharge to the front of the picture tube? Could that magnetize the CRT in such a way that the built in degaussing circuit can't clear it? I had at least 2 instances where I got static shocks to the front of the tube while I was hooking up the DVD player. I have a FRYS nearby and I'll go buy a degaussing coil if we can figure out how the CRT got magnetized. Thanks again for the help.

[vtech]

Relay/varistor combination provides the same results...no way you can go the "straight to AC route" without blowing something up.

Sounds like it is working then, can you see the effect on the tube too?
Sometimes internal circuit doesn't have what it takes to demagnetize but, usually is because someone has been playing with magnets around the TV or a lightning issue which is neither in your case?. You can make your own coil but a lot safer to get a hand-held one

At this point I'm not quite sure what you have?

[tvwatcher]

I do hear the thump sometimes when I turn the set on. Unfortunately I think my degausser circuit is somewhat different than you described. I believe they use this DSATR varistor from Panisonic along with a relay to control the on/off of the degauser and it times out after 3 seconds even if the coil is unplugged. I don't think I could be fast enough to plug the degausser coil connector on while hot to observe the screen for the pattern you attached. And basically it sounds like the degausser is working so now I'm back to ground zero.

If somehow the tube did get magnetized, are there times where you cannot demagnetize it with the built in degausser and need to use a hand held one?

What if I plugged the built in degausser coil directly into 120vac for say 5 or 10 seconds? Could I damage the coil? Should I put a series resistor inline to limit the current? Is it better to have the TV on or off during the degaussing process?

Thanks again for the help and sorry about all the new questions. I do have a BSEE degree and have been in the electronics field for over 25 years but I'll be the first to admit I know very little about TV's. However, I do know enough not to make the situation any worst than what it already is and keep myself from getting injured in the process!

[vtech]

As far as the cable box hitting the back on the set causing the problem? very much doubt it. you would have to physically move the magnets.
Do not have any schematic.

The degauser is very simple; All you have is a coil in series with a thermistor tied to the switched AC line. The purpose is to momentarily enrgize the coil to act like a big magnet around the picture tube for a short time to demagnetize the tube. (thermistors acts like momentary switch to reduce the AC)

Your meter readings sound correct. On some sets you can even hear a short "thump" sound coming from the coil. Better yet, start cold & try watching the picture thru a mirror as you plug the coil connector---you ought to see the effect on the picture. If you see it, it's doing it's job

similiar to this, may be not as strong for a very short time

[tvwatcher]

Well additional data on the problem, the degausser circuit works fine if I disconnect the coil - I get 120VAC for about 2 or 3 seconds at the connector terminals. However, when the coil is plugged it only makes it to about 3 VAC. The coil measures about 8 ohms so it does not appear shorted. Is 8 ohms a typical value for the degausser coil? Would you agree it appears the circuit that drives the coil is the problem? Would anyone have a schematic for the degausser circuit for Magnavox model HD2632 W103? Thanks for the help.

[Guest]

That reminds me that my Mom had the small Comcast cable box sitting on top the TV (it is a little bigger than a DSL modem). At some point while I was hooking up the cables, I moved the VCR a liitle to far and the cable box went crashing to the floor. When it slid off the top of the TV it probably hit the back of the TV's plastic case. So it didn't hit the magnetic ring assembly directly but it could have struck the outer case right in that general area. Do you think that a blow to the outer case could have nugged something out of alignment?

I looked at a bit at the degausser circuit. It looks like it uses a varistor marked DSATR and also is marked MMCC. Does anyone have the specs on this part?

Thanks for the help.

[vtech]

K, sounds like you know about the degauser. At least you can check it's operation

On the other hand, based on your description of the colors, there is no way that hooking up a DVD can do any of that? Thought perhaps the set was moved which can mess up the colors temporarily.

Other than the tube needing degaused, just about the only other thing is the magnet ring assembly which is fixed & mounted on the neck & never messed with ---hope you did not accidently knock agaisnt it? Can you post a pix?