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Degaussing RPTVs?

Discussion in 'Televisions' started by blue_harvester, Mar 7, 2005.

  1. blue_harvester

    blue_harvester
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    My 42PW33 RPTV has developed a red blur on the right had side of the screen, so I'm only after phoning Curry’s helpline to see what they said. The guy asked if my TV was near a radiator or HI-FI loudspeakers but I told him no. This is a little lie as my Eltax Liberty floor standers are sitting to the left and right of the TV. The reason I told him no was because I assumed that RPTVs aren't affected by speakers sitting beside them, am I right?

    Anyway, I have an engineer calling out on Wednesday, but in the meantime the guy on the phone said that I should disconnect my TV from all equipment and the mains for about 3 to 4 hours in an attempt to degauss the TV. Have any of you ever heard of this?
     
  2. Llanowar

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    Yes, that's the normal way to do it, i had red and green blurs too with my old speakers and did exactly the same and it removed them. Just get some magnetically shielded speakers or move them a bit away, cause it can cause serious damage over time. I think it affects every tv because of the magnetic fiels interfering, but i'm not 100% sure of that.
     
  3. Astaroth

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    RPTV (depending on type) will be affected by magnetic fields.

    A lot of modern TVs degause each time they are switched on from 'cold' (no need to disconnect or unplug). When it is turned on it will then automatically degause - on CRT TVs (non RP) you hear a 'clunk' sound as it happens (dont know about RPs).

    It may not fix the problem on a single attempted so do it several times and it should clear up the problem.
     
  4. blue_harvester

    blue_harvester
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    How far away should I move the speakers?

    At the moment they are about 2 inches away from the TV.
     
  5. LV426

    LV426
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    An RPTV may well be "affected" by magnetism, but not in the same way as a direct view CRT.

    Any magnetic distortion (e.g. from nearby speakers and radiators) on the CRTs inside will affect CONVERGENCE only - not colour balance.

    Manual degaussing near the screen will be of no benefit; the actual CRTs (which are the only thing that can be magnetically disturbed) are deep inside the set, at the bottom.

    If the colour balance is off in some part of the screen, then there is another cause - possibly dirt on one of the lenses, or ageing of one of the CRT tubes....
     
  6. blue_harvester

    blue_harvester
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    This is exaclty what I thought LV426. So hopefully I can keep the speakers where they are. Although I think I'll take the speakers away for the engineer coming out as that'll probably be the first thing he balmes it on!!
     
  7. scooby do

    scooby do
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    LV is correct convergence can be disturbed by nearby magnets.
     
  8. Zacabeb

    Zacabeb
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    There are no degaussing coils inside an RPTV and not even anything to degauss, since there is a triplet of CRT's, each monochromatic and lacking shadow masks. A competent engineer would not blame the speakers for the impurity.

    The color impurity may be caused by fungal growth in the liquid coolant. The coolant occupies the space between the faceplate of the CRT's and a plastic dome, forming a liquid lens that focuses the light into the lens assembly, and also dispersing heat away from the CRT faceplate. The coolant is usually composed of some form of glycol mixed with distilled water and possible other ingredients, the formulation being specific to the manufacturer and design of the CRT and lens assemblies. This is important for both the correct optical properties and the ability to cool the CRT faceplate.

    Fungal growth in the coolant can cause both halos and dark spots, depending on where in the coolant it sits and how dense it is.

    If the coolant has gotten infested in your set, you will need to have it (i.e. the coolant) replaced by a competent service center.
     
  9. blue_harvester

    blue_harvester
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    So you're saying there's no need to take the speakers away? I think I might just, as I couldn't be bothered with the hassle if the engineer starts fobbing the problem off as magnetic interference, even though this isn't the problem.
     
  10. lynx

    lynx
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    It would be prudent to remove them thus eliminating a convenient excuse from the technician if he's unable to locate a fault.
     
  11. Laurel&Hardy

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    I'd go along with that - move the speakers away, but in such a way that they look like they've always lived where you put them. In essence PJ's are less affected by magnetism than normal direct views, and as stated in another post there's nothing to degauss because there is no shadow mask in a PJTV. The red blur is more likely to be dirty lenses or contaminated coolant than a magnetic effect. Any TV engineer that blames the speakers is merely excusing the fact he doesn't have a clue why your set is faulty.
     
  12. blue_harvester

    blue_harvester
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    There's no where else in the room where I can move the speakers so I think I'll just move them upstairs and if the engineer asks (he will see the other AV equipment) I'll just say that my floorstanders haven't arrived yet.
     
  13. red16v

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    I'm interested in these comments that an RPTV would not be affected by magnetic affects - surely like any CRT it will be. Of course in the case of an RPTV purity would not be affected by magnetism affecting one (or more) CRT but surely geometry and especially convergence must be ? The only 'saving grace' that I can see over an RPTV CRT arrangement is possibly the CRTs are so closely mounted together that what might affect one CRT would affect all 3 and therefore whilst convergence might not be affected geometry would still be ? I have much experience of direct view crt tellys but none on RPTV tellys so I am curious. Regards, yt.
     
  14. scooby do

    scooby do
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    Convergence is disturbed by magnetic fields on RPTV. I have confirmed this on my Sony KP44 PS2. The onboard speakers are not magnetically shielded and if removed from the TV the convergence goes all over the place. I found this out whilst trying a sneaky method of mechanical focus on my set. Thought I would attack the set from the front and try to gain access to the CRTs through the speakers rather than dismantle the screen. Switched the TV on and the bottom of the screen was severly disturbed.
     
  15. LV426

    LV426
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    Quite right. And I did say exactly that.
     
  16. Laurel&Hardy

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    I did say PJ's were less affected, but they are still affected by magnetism. What I meant to add was that removal of the magnetic influence will remedy any convergence or geometry issues if they are present and caused by, for example, a pair of non-magnetically shielded speakers. Or conversely, in the case of Scooby Doo, actually introduce them because the fitted speakers are not magnetically shielded!! Bizarre design I must say!

    The difference is that with a DVTV removal of any magnetic influence does not remove the problems it has caused because of course the shadow mask is distorted, thus the need for a degaussing coil or, in extreme cases, an external ring with a higher degaussing pulse.
     
  17. scooby do

    scooby do
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    I think the Sony set just uses one of their range of car speakers for the KP44 PS2 thus not magnetically shielded as it dosen't matter in a car! Not tried removing the speakers from my 57WH36 to see if the same applies but guess not as I'm sure someone else would have noted the effect.
     
  18. red16v

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    An external magnetic field will affect the electron beam 'trajectory' towards the shadowmask and through to the phosphors on the front of the screen. If you place something with a strong magnetic field near the crt you can induce a magnetic field in the shadowmask/rim band and even the aquadag etc which as I say affects the beam trajectory. The shadowmask is not distorted by this magnetic influence - it is 'pockets' of residual magnetism which can remain (on the shadowmask and indeed any metalic item) which causes the unwanted beam trajectory interference after the original source of magnetism has been removed. The purpose of degaussing the crt is to remove this residual magnetism - not to 'un-distort' the shadowmask. A shadowmask is of course a thin sheet of metal perforated with millions of holes and lies just behind the phosphor coating on the inside of the crt, it is clipped into place. Despite its somewhat 'flimsy' sounding construction it is in fact quite robust and it would be difficult to distort it. The only ways in which I have seen a problem which could be blamed on a distorted shadowmask was when/if the telly is subjected to a severe mechanical shock or if an overenthusiastic 'engineer' waved a particularly powerful external degaussing magnet near the cente of the crt -the actual strength of the external field can permanently distort the shadowmask ! I hope this info may prove useful. Regards, yt.
     
  19. Zacabeb

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    Trinitron aperture grilles however can supposedly get distorted, and rough handling (especially with the screen faceplate facing down) of CRT sets can (again, supposedly) shift the entire shadow mask on its mountings enough to cause distortion. I haven't witnessed either thing happen in person though. :)

    I love RPTVs and miss the one I had. If it hadn't been 4:3 and the convergence board lacking compensation for 60Hz, I would have paid to get all the CRTs replaced in it instead of buying a new, direct-view TV. With properly set up convergence and focus, the picture on that TV was awesome. It's a pity they require such high maintenance.
     
  20. red16v

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    Hi Zacabeb, CRT tv's should never be stored face down - the reason being that any possible debris (left over from manufacturer of the electron gun assembly) can fall down from the gun assembly and end up on the rear of the shadowmask causing a 'spot' failure. Sometimes this can be cured by 'smacking' the front of the crt but I have never witnessed a successful 'cure'. Having said that when I recently bought my Toshiba telly the 'unboxing' instructions specifically told you to upend the tv set onto its face to remove the box - very very naughty. Regards, yt.
     
  21. Laurel&Hardy

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    If they are the same speakers that are in my 51WH then they are magnetically shielded.
     
  22. scooby do

    scooby do
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    Obviously toshiba put a bit more thought into the effect a magnet would have next to the CRTs. Not that it causes a problem on my Sony but just something I noted during experimentation
     
  23. blue_harvester

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    Got my TV replaced today and the new one seems fine. I've put the speakers back to where they were so if the problem comes back I'll def know that's it's something I'm doing!

    Thanks for all the advice guys.
     
  24. MQUIN SKYWALKER

    MQUIN SKYWALKER
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    My Pw33 Has Got That Exact Fault It Started Last Night After Only Four Days It Must Be Something At Fault With These Sets
     
  25. blue_harvester

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    Where'd you get the TV, Curry's? Have you reported it yet? They were actually really good about replacing my set, had everything sorted within a matter of days. Here's hoping my new set doesn't go the same way!

    BTW do you have speakers near you TV?
     
  26. blue_harvester

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    Damn TV has started showing the red blur again!!!!!

    Although this time it is a bit lower and not as big. Should I just keep it? I don't think it'll annoy me as much as the last red blur! Still, it's £650 I paid out!!
     
  27. pharris007

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    Sorry I will never buy a Toshiba RPTV again.

    mass problems with red streak, mass problems with a bright streak running down the centre of the screen, especially when the camera pans from side to side.

    Toshiba said this was "normal". yeh right :mad:
     

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