HD TV Help (Audio related)

[sonny]

I have an older Sanyo HD TV that my brother has graciously given my family. I love it but it will emit a high pitched squeal that will stop momentarily when I shove something under the tv, but it will eventually come back. I've been told that this is a simple fix and I have also been told I will die if I try to repair it myself. Has anyone experienced anything like this?

smith288 nee not answer

[WebScorpion]

I'm guessing you are talking about a CRT type television, not LCD or Plasma. Anyway, you probably already know it, but just in case, there can be a massive charge of electricity in the tube even when it's unplugged, so be careful. There's a nice electronic hobbyist web site called the Sci.electronics.repair FAQ which might be of some help. Here's what I found on the subject there:

If you are desperate and want to check the inside of the set:


Using appropriate safety precautions, you can try prodding the various suspect parts (flyback, deflection yoke, other transformers), even lowly ferrite beads, with an insulated tool such as a dry wooden stick. Listen through a cardboard tube to try to localizing the source. If the sounds changes, you know what part to go after.

Once you have located the guilty party, some careful repositioning, a strategically wedged wooden toothpick, or a dab of RTV silicone or hot-melt glue may keep it quiet. Where the yoke is the guilty party, see the section: Reducing/eliminating yoke noise.

It is possible to coat the flyback transformer, but this is used mostly when there a loose core or windings and you are getting not only the 15,735 Hz horizontal (NTSC) but also various subharmonics of this. This is probably acceptable but may increase the temperature of the flyback.

A replacement flyback (or whatever part) may cure the problem unless it is a design flaw or manufacturing quality problem. However, the replacement part could be noisier. You really do not want to replace the yoke (aside from the cost) as convergence and other service adjustments would need to be performed. Other transformers can be replaced.
Note that the deflection frequency - just over 15 kHz for NTSC and PAL - is on the border of audible for adults but will likely be loud to younger people possibly to the point of being terribly annoying - or worse. If you are over 40 (men more so than women), you may not be able to hear the fundamental at all (at least you can look forward to silence in the future!). So, even sending the TV back for repair may be hopeless if the technician cannot hear what you are complaining about!

BTW, if you have a really old tube type TV, the power tubes (damper and horizontal output) can also whine but these sets are few and far between these days :-).

[sonny]

thanks! I'll probably have to get someone who doesn't mind getting shocked to do this.