Baxandall CCFL inverter transformer ?

[shakalnokturn]

I'm trying to repair a LeSiglent toy DSO that has cooked the BJT's and control MOS on its single CCFL inverter's primary side.

Replacing the transistors restored backlight but transistors are running much too hot.

Anyone know of a cheap source (disassembling a ready made module is an option) for these Baxandall (/Royer) inverter transformers?

[T3sl4co1l]

Do you know that the transformer actually has a fault?

Those circuits usually just run hot.  150°C isn't much of a problem for semiconductors, if not great for lifetime.  Even at merely 80°C it'll feel very hot (too hot to touch) while being quite reliable -- I don't know what metric you're using to evaluate the thing here.

To improve reliability, it might help to simply add some heat spreaders/heatsinks and thermal (gap) pads to reduce peak temperatures.

Tim

[shakalnokturn]

I'm not absolutely certain the Xfrmr is defective.
I know these Baxandall converters have low efficiency at the best but within a couple of minutes the TO-251 transistors are at 90°C (measured with thermal camera), current consumption is 2.2A (@6V).
Letting the inverter run 10 minutes led to one of the transistors shorting.

Any clues on where to find such transformers?

Thanks.

[T3sl4co1l]

Can you measure the transformer's small signal parameters, say with a signal generator and AC voltmeter or scope?

Tim