What is the fifth tap on this transformer for?

I took apart a microwave, because it's not in my nature to throw anything broken away without disassembling it and seeing how it works first. Don't worry, I have absolutely no intention of powering it up. I'm going to use the copper coils for another project instead.

Here's the transformer specs.


On one side of the transformer is the primary and secondary coil, they both have continuity between each of the leads, both the red wires on the top, and the two spade connectors on the bottom.



However, the other side of the transformer has a single spade connector, that does not have continuity with the casing, or either the primary or secondary coil, and I can't find another tap anywhere near it, and it has no continuity with any part of the transformer that I can find. Connected to that wire was a 5 kV, 0.3a glass fuse in a holder, and I didn't pay attention to what it came off of originally.



Any help in identifying and what that fifth wire is would be greatly appreciated.

That's the high voltage output. The other end of the winding is connected to the frame (ground). The red wires are low voltage (step-down) for the Magnetron's filament.

sollap said:

That's the high voltage output. The other end of the winding is connected to the frame (ground). The red wires are low voltage (step-down) for the Magnetron's filament.

Click to expand...

I wasn't able to get any continuity between that wire and the frame, although it's entirely possible that that's why the microwave broke in the first place.

If that's the high voltage tap, what are the two tabs underneath of the red wires that are connected to an additional coil for? Is there a third coil in there that I'm just not seeing?

Thank you for the response.

The two tabs at the bottom are the primary. The red wires are not likely connected to a coil, the wire itself is just wrapped around the other windings a couple of times. I think the output is supposed to be around 3 volts.

Yeah, the tab on its own is the HV output, the loop is the supply for the magnetron heater.




$29 for a new one https://www.certified-parts.com/96120xb-1-galanz-microwave-high-voltage-transformer-gal-900u-2

I figured out the problem, the high voltage coil is shorted / broken somewhere, which is why I wasn't able to get continuity from that terminal to anywhere else. That also explains why the magnetron stopped working.

Thanks for the help guys.

Really, transformer failed not magnetron?
I've assumed magnetrons were what wore out.

I've disassembled a couple, used diodes and caps to rectify output of a Hypot, used for DC testing of MOV (small ones can be tested with AC, larger carry too much current due to capacitive reactance.)

I have a high voltage pulser (10kV capacitance and trigger mechanism, think) that I would also power up with DC source. Haven't tried yet.