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I was working so SeanB beat me to it. It's a nice little 30VA 115/200V 3 phase 400Hz bench supply. Mains in 400Hz out.
Probably part of a test set for a small gyroscopic instrument. 30VA would not power much else.
Bit of a shame to break it up but I dont think you will have much use for it. You could use it to run an aircraft type cooling fan but it would be a screamer.
No not breaking it up just yet... now I have been told it might be sellable !
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/xevil.gif.pagespeed.ic.tdrs7Uj5gu.png)
I just powered it up !!! Still alive... but I DID fear for my life
![Scared :scared:](https://www.eevblog.com/forum/Smileys/default/scared.gif.pagespeed.ce.oZptHNcbsD.gif)
I probed the 3 pins of that weird pwoer connector at the back. One of the pins was clearly connected to the chassis, so I called that earth...
The other two pins, live and Neutral, I get 20+ Mohms between them, and between each one and earth.
So no short. So I powered it up... via my dim bulb tester.
Imeediatley it light up solid and brigght and the intrument emitted a loud and freaking scary "HV" like noise, " Tggzzz... zzz..... high pitched ". I panicked thinking the caps would blow on me, so I turned the DBT off immediately. Waited a bit, applied power agzain a few seconds... noise started to diminish, and the DBT got less and less bright hmmmm.... caps reforming eh ?!
After a few quick cycles, eventually the noise stopped. It was coming from the transformers, don't know which one(s), was unclear.
So then started playing with it.
Measured voltage and ripple on all 6 filter caps. Two read about 40V and the other about 20V. Ripple is not stellar but not catastrophic either. Like 200mV at first, then some dropper down to tens of mV after a few minutes.
Then I looked at the meter movement at the front. It's dead as a dodo. Device is not dead though : if I measure the voltage on the front jacks I do get something plausible : using the fine tune pot I cna vary the voltage between 185V and 230V. Nominal is supposed to be 200V, so that's good it looks like. so I set it to spot on 200V. That was with the rotary switch set to position ' 3 '. If I then switch to positions ' 1 ' or ' 2 ', I get 100V instead of 200V.
As I was fiddling with the fine tune pot, it would randomly make the transfomer make this scary noise again ! Scared the shit out of me. Again as soon as the noise would come up, in unison, 100% correlation, the DBT would lit up brightly. However after exercising the pot a few times from lock to lock, eventually the transformers would remain quiet at all times.
so I started to be a bit, just a bit, less scared that this instrument would blow ni my face.
So I then got adventurous and started to direct my attention at the rear of the instrument this time, and scopes the outputs.
2 pins for each pahse, and oen pin for ground. I made sure the ground pin was connected to earth/chassis, which it was. Gave me some confidence that I could probe all these outputs without blowing my scope.... So here it is below.
That's Phase 2 and 3. I don't know why there are two pins for each phase... maybe floating ? Or maybe simply connected together, simple as that... will need to figure that out. Anyway when I probe either pin of a given phase, respective to ground, I get exactly the same signal.
so as you can see they are 180° apart not 120°. Oh well....
Outputs are nice, clean sine wave, stable in both amplitude and frequency. Frequency spot on at 400Hz, so that part is working...
These two phases are not exactly the same amplitude. One is slightly over 150V peak, the other slightly under. Not the end of the world I guess...
What about Phase #1 you ask ? Good point.... this one definitely has a PROBLEM : amplitude is only 4.4V AVG on the DMM ! Also, amplitude is unstable, on the scope it "wobbles" between 6 and 7 Volts peak, or thereabouts. Looks like a capacitive effect to me. Maybe this particular phase runs off of its own filter caps and they are worse than the others. That might explain the wobble but won't explain the massive drop in amplitude.... so I guess..... oh no... I guess I have now officially a new TE to fix ?!!
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif.pagespeed.ce._hfWAz_QHO.gif)
No schematics no nothing and zero knowledge of how these things work at all
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
... wish me luck