In a way, yes: if you have a switched power supply, it could be (rather
small)
mains transformer that is vibrating at high frequencies. But with an
analog PSU,
it humms at 50-60 Hz, this is not "squealing", no....
OTOH, flybacks are often sealed in plastic and vibrate **inside** the
sealing.
I never managed to stop a monitor from beeping and squealing (nice word
8-),
except by replacing the flyback transformer or by treating it with a
very small
hammer (really!!), trying to "shake it into shape". Don't do this at
home!
ms
Iggy Drougge wrote:
>
> Tony Duell skrev:
>
> >> >The squeal from most monitors/TVs comes from the flyback transformer
> >> >(horizontal output transformer, line output transformer, call it what yo=
> >> u
> >> >will). THe core vibrates at the horizontal scan frequency.
> >>
> >> Is that the neck at the back of the tube? I see a key-like screw protrudi=
> >> ng at
> >> a 90=B0 angle from the neck, which seems to be coupled to a metal band wr=
> >> apped
> >> across the neck.
>
> >No, that's the deflection yoke. The flyback transformer is on the PCB
> >normally. The easy way to find it most of the time is to follow the EHT
> >cable from the flare of the CRT back to a plastic-encased lump on the
> >PCB. That's normally the flyback transformer (it could be a voltage
> >multiplier in some older colour monitors, but I don't think that's an
> >issue here).
>
> All right, I stole some sticks of hot glue from the scale modellers and poured
> it onto the thing which looks like this:
>
> ,-----------.
> | _ |
> | | |WARNING|
> | | | HIGH |
> | | |VOLTAGE|
> | | | |
> |_| |_______|
>
> It sits on the main board in the monitor section, connected to that dangerous
> red wire fit with a suction cup onto the CRT itself.
>
> But it doesn't really look like something which will vibrate or rattle in any
> way. I've done some reading up on flybacks, though, and apparently there are
> some advanced wirings inside that package.
>
> Then I let it dry and turned it on. Still the same horrible sound. I walked
> around the thing for a bit, and it seemed as though the noise emanated from
> the black cage containg what is probably the mains transformer.
>
> A recent posting in the ongoing "wobbly PET" thread suggests that some sheet
> steel contraption inside the PSU is dissolving and vibrating at mains
> frequency. Could this be the case here?
>
> --
> En ligne avec Thor 2.6a.
>
> The generation of random numbers is too important to be left to chance.
--
Michael Schneider email (home): ms_at_silke.rt.schwaben.de
Schleestr.8 http://www.vaxcluster.de
72766 Reutlingen Phone: +49 7121 492781
Germany FAX: +49 7121 479331
People disagree with me. I just ignore them.
(Linus Torvalds)
Received on Sun Oct 07 2001 - 04:53:58 BST