how to TEST a transformer to know if it’s good or bad

[ghytd]

That's a good starter idea to just check continuity on the coils sure.
But often when a coil starts to fail, the very thin clear coat insulation on the wires start to break down and effectively this changes the number of coils from X to a fraction of X. When this happens, the INDUCTANCE changes on the transformer which is kinda like the coils resistance. And this change in coil counts will change the output voltage on the secondary coil.
So checking the continuity is fine, but you should also check the actual inductance of the primary and secondary coils to see how degraded the transformer is. This is where it helps a little to use an analog multimeter instead of a digital. An analog will show the needle move as resistance is detected.
In your video, this secondary coil was open meaning it probably burned through. It probably was pretty degraded before it burned through though and you may have been getting improper voltage on the secondary coil.

[noanyobiseniss]

Now do a vid on how to find data sheets on these chinese transformers with number that dont search. :P

[kevinburrell]

I’m confused on how 160 ohms is a good electrical connection. Isn’t that extremely high ?

[jfmanaois]

how did you identified the coil diagram?

[vtradio]

Would this be the same test for an audio transformer?
73 Paul AA1SU

[ceecee-rr]

Hi, can you explain how do you know the lower coil doesn’t have a connection please .

[rahinravi]

If a short circuit how we rectify that

[Dee-kf]

Whats your meter setting? Ohm 200? 2k? 20k? 2M? 😅 Wouldnt that be some handy info to give?

[marcoantoniomejiamedina]

It’s great to have you cover the multimeter completely or forget to show us what setting you put it on. Wow

[jimle]

Sorry but everything was in shadow and I coi;dn't see any readings or anything. I will take your word for it.