Squealing CRTs

From: Iggy Drougge <optimus_at_canit.se>
Date: Mon Oct 8 21:55:40 2001

Tony Duell skrev:

>> >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:

>The place to put it is between the ferrite core and the block containing
>the windings (with all the connecting pins on the bottom)

IOW, between the big block and the little handle? That was hard to reach.

>> ,-----------.
>> | _ |
>> | | |WARNING|
>> | | | HIGH |
>> | | |VOLTAGE|
>> | | | |
>> |_| |_______|

>That looks just like a flyback transformer :-)

It looks like a kettle to me. =)

>> 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.

>Sounds like a switch mode PSU. Any transformer can vibrate, such as the
>one in the SMPSU circuit. Now, it should oscillate at an ultrasonic
>frequency so you won't hear it, but dried up capacitors in the SMPSU
>circuit can make the thing drop in frequency, sometimes with no other

The old dried up capacaitors problem...

>If you can get an ESR meter (and IMHO if you repair monitors or SMPSUs
>you _need_ some way of measuring the effective series resistance of
>capacitors) then you could test all the electrolytics in the power supply

I don't intend to take up high-voltage repairs as another hobby of mine. I'm
too intent on keeping on living with all my bodily functions intact.

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Received on Mon Oct 08 2001 - 21:55:40 BST

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