Buzzing flyback


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Buzzing flyback

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steve_d
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Feb 21, 2008, 10:30 PM

Post #1 of 8 (1632 views)
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Buzzing flyback	Can't Post

Hi! First time here.

I have a 27" Mitsubishi circa 1991 that works great except the flyback has been buzzing for years. After searching here and googling, it seems the fix is to coat it with an acrylic, polyurethane or flexible adhesive. My problem is the flyback seems to be totally sealed and I don't see how I can get any substance into it. Any help would be greatly appreciated! Thanks!

techchris
Veteran

Feb 21, 2008, 11:03 PM

Post #2 of 8 (1627 views)
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Re: [steve_d] Buzzing flyback [In reply to]	Can't Post

you cant get in but sometimes taking it off the board and tightening the metal clip that goes round the bobbin will shut it up.make sure its not the linearity coil nearby that is making the noise, as it sounds similar.

steve_d
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Feb 22, 2008, 6:56 AM

Post #3 of 8 (1617 views)
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Re: [techchris] Buzzing flyback [In reply to]	Can't Post

I'm fairly sure it's the flyback because when I tapped it, it got louder. I was wondering if maybe I could make a small hole in the plastic with an exacto to get something inside?

techchris
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Feb 22, 2008, 10:55 AM

Post #4 of 8 (1614 views)
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Re: [steve_d] Buzzing flyback [In reply to]	Can't Post

no definitely don't do that.use a plastic insulated stick to prod around to make sure it is the flyback transformer.if it is you could try covering it in silicone but dont switch back on till it has dried .if that does not work then change the transformer.

rrobor
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Feb 23, 2008, 10:34 AM

Post #5 of 8 (1601 views)
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Re: [steve_d] Buzzing flyback [In reply to]	Can't Post

I have seen a piece of plastic used between the coil and the bar at the side, this is wedged in to maintain pressure. To find whats whistling use a screwdriver, hold the blade on a safe part of the object to be tested and stick the handle in your ear. You can use lacquers etc on open coils and yokes but not on this. Dig a hole in the transformer and you are into the overwind with 25KV there and after that all you will se is flames.

steve_d
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Feb 23, 2008, 5:04 PM

Post #6 of 8 (1596 views)
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Re: [rrobor] Buzzing flyback [In reply to]	Can't Post

I realize I don't want to be digging a hole in the xfmr windings, but I was looking at the flat area on the back above the focus and screen pots. It seems like there would be some open area inside there.

rrobor
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Feb 24, 2008, 9:35 AM

Post #7 of 8 (1585 views)
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Re: [steve_d] Buzzing flyback [In reply to]	Can't Post

Dig into that and fill that all you will do is glue the screen and focus pot, you will not fix your issue. A transformer like this is not the usual culprit, be very careful jumping to conclusions. Remember if you push the transformer you are bending the board and causing differences over quite a wide area. I once changed a flyback only to find it was a resistor whose legs went down a standoff pipe, Filled the pipe with solder and cleared the fault. so take care.

steve_d
New User

Feb 27, 2008, 6:07 PM

Post #8 of 8 (1567 views)
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Re: [rrobor] Buzzing flyback [In reply to]	Can't Post

In Reply To

A transformer like this is not the usual culprit, be very careful jumping to conclusions.

Good call! It wasn't the flyback. If you look at the first pic in my original post, there's a little coil with a white cover at the bottom center of the pic. Popped the cover off and it's quiet as a church mouse. There's a metal clip under the cover that was singing like a canary. Thanks for all the help. This is what I love about the internet!

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