Is it worth while buying a ring tester for testing high frequency transformers?

What I mean is. Will I get a good-bad reading from an unknown transformer?

Is there another way?

I have a power supply that overheats the Mosfet and transformer. Outputs about half voltage and shuts down.

I've eliminated loads one at a time with no change.

New board is coming, but I never pass up a chance to learn something new.

 

Like this one.......................

 

How about ringing with a shunt capacitor and a dc pulse?

Or watching on a scope while fed with square wave?

Wouldn't need a tester then.

But will it show a shorted turn?

 

I guess I'll answer myself.
And save some money.

Feeding a 100khz square wave to a donor transformer makes a beautiful ring pattern on scope.

Tomorrow I'll look for one with a loose enough winding, to wind a single shorted turn to see how much it damps.

Then on to the suspect.

 

This is a very simple shorted turns tester I built about 30yrs ago & still use it for SMPS transformers.

 

Explain how it works in practice.
Do you need a reference to tell you whats good or bad?

 

Like this one.......................

I have a Blue Ring Tester and it works great. I bought mine as a kit when I started learning electronix last year so I could also practice soldering.

 

OOps, This is the circuit that's used in the previous tester. It runs at about 25Khz when tested with a freq meter. RV1 is adjusted to give just over full scale deflection on the meter. Tr2 is the meter amp. When testing a SMPS transformer, connect leads to the primary windings. If there is a shorted turn in the T/F the meter will drop back to a very low reading, due to excess loading on the oscillator circuit.

 

I think this will work best for me.
Shorting one turn with xacto knife flat-lines.

 

I built this one some years ago, Instead of discrete LED's for the bar graph, I used the DIP sized bank to make it compact.
http://wenku.baidu.com/view/ea87f920af45b307e87197f4.html
Max.

 

Tested the real transformer today. Found it ringless.

That means my 3 weeks work on this set is for naught.

Even the new PS supply order was canceled.

Any TV guys on here with junk boxes?

LG 47LB5D

 

Finaly found the original article. Have recently wrecked an LG LCD TV that had a picture problem. But I only saved the switching MOSFets & diodes & binned the rest. Pretty rare for the transformers to be faulty.

 

Finaly found the original article. Have recently wrecked an LG LCD TV that had a picture problem. But I only saved the switching MOSFets & diodes & binned the rest. Pretty rare for the transformers to be faulty.

First for me.

Rare for 10 other parts to fail too.

Tried to get a new board twice. Out of stock.

Found a schematic and parts list. Not helpful. ZD100 not listed nor transformers.