Are sinusoidal distortions of rectangular pulses related to overload or insufficient power supply 10 - 20 V ?

Oh those were because of my crap oscilloscope and I can't edit older posts . I passed to devide by 10 on probe and no distortion. Signal look decent square wave on primary coil to ground.
At 20v on input coil to ground I get a Vpp of around 15V (square wave) . If I measure directly on the coil signal looks like sin wave and has around 500mVpp at 20v input. If at 20v it is 500mv at 400 will be 10v maybe?

Maybe.

I forgot to mention that the rectifying bridge has one diode the a like 20-30 points lower value than the other 3. I used a 12Vac source and I injected on input of psu and with oscilloscope I measured on big capacitor for any distortions. I found nothing . Can this cause problems at 400v?

Bridge is in the circuit or desoldering ?

In circuit. I put 12Vac instead of 220V in psu. I got no distortion at 12v.

I want to build this to test smps transformers
https://www.google.ro/url?sa=t&source=w ... KrxUuzZNsm

You should change this bridge by a new one for your safety )

Mosfet gate transformer has 1.356mH @ 1kHz 1 - primary and 2 separate secondary coils.
Primary coil of the main transformer - 752uH, 180nF capacitor, 62uH - aux L.

Measured in Zalman 750EBT psu. Also it has 2 PWM mosfets dead - 5r190CE, one IRFB7437 in sec. side, bridge GBU1506, FUSE/ Maybe something else )

Wew then my transformer maybe it has a short. I tried to measure inductance on primary coil directly in circuit and I was unable (I have a cheap fcl meter}. I measured a bigger coil and add it in series and the difference was 1-2uH for primary hmmm. It can have such low inductance? From a paper I read they say yes but I don't know. I tried to build that blue coil ringer from the link in last post but I don't have the cd4015 so I put oscilloscope directly instead of the ic to see the impulses. On some coils I can see 5 6 impulse but on primary of the transformer maybe 1 pulse. Any other way to measure that transformer is OK? Maybe I will desolder it. If it is dead any chance to find other or repair it? Thanks

What is your advice (read last post) thank you

Primary coil of the main transformer in no LLC PSU - 1.5mH, so if you have <750uH - it's strange.

Measure it without circuit.

It an no llc psu? It is llc

Must be around 700-1500 uH. If < - transformer possibly dead.

It is 1-2uH :( anything I can I do? It can drop from 700+uH to 1?

take a photo of the transformer please.

must be about 750uH

Thank you. I can't get it out from circuit witn 60w iron :(. Hot air will distroy pcb I think. Any chance if transformer is in short to do something? Replace it or repair it?

No need to get it out from circuit. Remove only MOSFETs as I did and measure the coil. As you can see your and mine PSU have the same platform. Dead main transformer - very rare situation.

Replace it or repair.

Ok thank you. Where I can buy this? Aliexpress? The code is strange on it what to search?

Also how to remove it?

only from psu on the same platform and power. There is no other options.

Repair transformer any chance? I desolder it and same readings 1uH. Aux coil has 50+uH and caps 180nF
I have seen on YouTube that they boil them to open magnetic core. But after you need special glue or something? And I can use same wires and same protection tape or is destroyed?

Depends on topology, some transformers have an unmagnetic gap in the central, some not.

Yes. Be careful.

Need to replace a shorted wires by a new one. Very important to turn it wire by wire. Also in right direction.

Mylar is used as an isolator. Also you can use Captone.

I was unable to open it without breaking it :( they put melted plastic over the ferite and I was unable to remove it without breaking the core. Sad. The primary was in short after I open it I detected that easy. Any chance to find another transformer somewhere similar to this? It will not work if glued like this no? :)

it is an epoxy compound. You must boil transformer before try to remove it. You can buy core or try to open another one. It is STD-39 (39mm width)

It is important to set up right nonmagnetic gap.

I boiled it the core separate in both but the melted thing did not let it free. I use a screwdriver and by mistake i break it. The center is not round so hard to find replacement ferrite. It is oval.

Take a photo of your transformer now.

I glue it I will try to assemble and see if I get 750 uH but I doubt it will work again.



Posted after 2 hours 15 minutes 17 seconds:
I reassembled it as I could and I have like this:
No core inserted primary coil 13uH
With core as close as I can press with hands has 330uH hmmm :( . Maybe is different from that with 750uH?

primary coil consist of 2 coils. did you assebly as it was? number of turns, winding rotation, and so on? Your core looks like normal.
It also may help someone someday if you write here N of turns

For example:
I - 50 turns d=0.5мм
II - 10 turns 3x0.6mm

Primary is only 1 coil made of many very small wires in paralel so diameter is hard to tell because you can't make circle (it is around 1.5mm) 28 turns . And secondary is made from copper foil put on some isolator and has 15mm wide with 4 turns with median connector. Second coil for - 12V it has 2turns of 0.5mm. Yes used same direction. Only at the - 12v coil I'm not sure of direction of those 2 turns.