john12ax7

Testing Transformers - Test Jig?
« on: May 16, 2020, 10:31:20 PM »
Have a bunch of pcb mount transformers to evaluate and wondering how others approach this.  Thinking of making a type of universal pcb with sockets that they could be plugged into. 


abbey road d enfer

Re: Testing Transformers - Test Jig?
« Reply #1 on: May 17, 2020, 04:16:32 AM »
Have a bunch of pcb mount transformers to evaluate and wondering how others approach this.  Thinking of making a type of universal pcb with sockets that they could be plugged into.
Considering there are so many different footprints, and the usual test requires accessing only one primary and one secondary at a time, I would suggest you use croc clips suited for the task
https://www.mouser.fr/ProductDetail/Pomona-Electronics/5788-0?qs=BG8onI7C4yr33%2F4NCbVZxA%3D%3D
Usual MiniGrabbers are too small and not retentive enough in most cases.
I would also suggest you get a piece of 12 gauge steel of about 16"x12", connected to ground, that will protect from electrostatic and magnetic interference. You'll want to cover it with some insulating material.
What type of tests are you intending to do?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

john12ax7

Re: Testing Transformers - Test Jig?
« Reply #2 on: May 17, 2020, 04:44:43 AM »
Looking to do objective tests, (frequency sweeps, distortion, cmrr, etc) and subjective listening tests (imo they all tend to sound a bit different). I have BNC and XLR to clip leads that I normally use, but the main concern is that this will be introducing different parasitics than what will be in actual use. PCB mount vs flying leads is not necessarily the same thing.

The dimensions are sometimes different, but the corresponding connections are generally in the same quadrants, so would seem at least partially doable.

abbey road d enfer

Re: Testing Transformers - Test Jig?
« Reply #3 on: May 17, 2020, 05:43:56 AM »
Looking to do objective tests, (frequency sweeps, distortion, cmrr, etc) and subjective listening tests (imo they all tend to sound a bit different). I have BNC and XLR to clip leads that I normally use, but the main concern is that this will be introducing different parasitics than what will be in actual use. PCB mount vs flying leads is not necessarily the same thing.
Actually, if your concern is with parasitic capacitance, you should concentrate on the connection to your test equipment and said equipment own input impedance. Capacitance of a PCB trace is only a few pF, not too dissimilar to flying leads, but 1 meter of BNC cable adds about 30pF.
If you want to assess a typical 1:10 mic input xfmr, you must use an active probe ($$$), or make one ($0.50).
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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