Samsung 240T Sizzles

[srlarkin]

Hi,

I've got an old Samsung 240T monitor. It started making a buzzing/sizzling noise and emitting a burning smell. The display was fine.

I opened it up on the bench and noticed the buzzing was coming from some transformers. I replaced 3 330uF electrolytics but it had no effect. After the replacement I also noticed some transformer sparking as well.

Note that there is no noise or problem until I hit the power button on the monitor.

Any advice on salvaging this would be appreciated.

[PlainBill]

Re: Samsung 240T Sizzles

Hi,

I've got an old Samsung 240T monitor. It started making a buzzing/sizzling noise and emitting a burning smell. The display was fine.

I opened it up on the bench and noticed the buzzing was coming from some transformers. I replaced 3 330uF electrolytics but it had no effect. After the replacement I also noticed some transformer sparking as well.

Note that there is no noise or problem until I hit the power button on the monitor.

Any advice on salvaging this would be appreciated.

I see one problem - the replacement caps you used are almost certainly not low ESR, and wouldn't last long in this application.

Other than a couple of dark shadows on the back, I don't see signs of the arcing you mentioned. Could you indicate the spots?

When I hear about a hissing sound, or arcing, I think about the leads to the CCFLs.

PlainBill

[srlarkin]

Re: Samsung 240T Sizzles

PlainBill,

Thanks for replying so quickly.

The caps are temporary I know; they were the set I could get quickly.

The arcing comes in the top middle transformer on the right hand side. It is a fairly stead glow when the power is on and can be seen thru' the bottom of the pcb.

Thanks Again!

[alexanna]

Re: Samsung 240T Sizzles

There is a possibility one of the HOT wires has come loose from one of the CCFLs.
Try substituting a known good CCFL for that coil, or if you have room swap CCFL connectors.
If there is a problem with the CCFL wiring it will follow to a different coil.

Edit:This should done momentarily, and power off immediately.
Thinking about it some more, it would be best to rule out a shorted secondary winding in the coil/transformer first.

[srlarkin]

Re: Samsung 240T Sizzles

Alexanna,

Thanks for your ideas. I did in-circuit continuity tests on the coils and they seem symmetrical. I'm not sure I could get replacement transformers in any case (no luck with lcdparts.net).

I did not check the connections on the CCFL side because I am leery of damaging anything. I did make sure the connectors on the inverter boards were okay.

So now I've ordered a replacement inverter. Hopefully this will solve my problems. I'll know in about 20 business days...

... if not, I'll have to open the monitor further and go right to the CCFLs.

Thanks again,

Steve
p.s. swapped CCFL cable and still got sparking from transformer. Tried without anything plugged in and more sparking. I've also notice the varistor (small blue component in front of each xformer) is starting to crack.