[Boatanchors] Question for the group

[J. Forster]

Same as my last post, except the display was set up to display a voltage on one
axis and a current on the other. It's essentially a phase diagram, whereas I
described a time domain display. Whatever display you prefer. Again, it's hard
to make measurements, but is useful for comparisons.
-John

eldim at att.net wrote:

>
>
> Hello Gary, John, and all interested parties,
>
> Back in Joplin, Missouri in the mid sixties I knew a brilliant retired
> engineer from Bell Tel who demonstrated ringing flybacks, coils, transformer
> windings, and toroids using a Oscope and a pulse generator.  He had a military
> AN/USM-24 Test Set, AN/USM-50 is also a good equivalent, which he used to ring
> these devices. By the way, these were very nice RADAR Test Sets which had the
> Scope, Pulse Generator, and some other bells and whistles built into one
> compact unit. Our RADAR section at our SAC RBS site had both of these test
> sets still in use during that period.   I'm not an expert on this test set-up,
> but if memory serves me correctly he fed the pulse in series with the DUT to
> the Vertical Input and also to the horizontal input.  The exact electrical
> hook-up is unclear to me since I never did the test myself.  I was just a
> young AIR FORCE Radio Maintenance Repairman  fascinated by this gentleman's
> vast kno! wledge of  TESTING devices, etc. The I do know that he had to
> experiment with the pulse width and frequency to prodruce a clean ring that
> was suitable for viewing on the O-scope. The cleanest ring is that of a Toroid
> inductor because of the manner in which it is uniformly wound.  If you try to
> visualize a perfect christmas tree on its side, and then another identical
> sized tree in series, and so forth, then you would see visually what a good
> coil was.  A good coil would ring with many waves that would gradually reduce
> to nill until the next pulse started the ring again.  ONE SHORTED TURN would
> cause the coil to dampen rather adruptly, indicating a defect.  You need to
> disconnect any parallel resistance paths that would prevent making this test.
> i.e. on the TV yoke there are two resistors on the vertical windings that
> provide the proper aspect ratio. I'm sure that there are some far better folks
> out there who could shed more light on this intere! sting subject.  I know
> that I'd be the first to be interested to hear from your, especially the
> hook-up diagram.
>
>
>
> Best regards,
>
> 73,
>
> Glen Galati, KA7BOJ
>
> Tacoma, WA
>
> email: eldim at att.net or eldim at worldnet.att.net
>
>      -------------- Original message from "J. Forster" <jfor at quik.com>:
>      --------------
>
>
>      > It's a fairly old technique to estimate the Q of a coil and look
>      for shorted
>      > turns. Basically you set the coil up with a capacitor (either
>      stray or an
>      > external C) and apply a pulse and watch the damped sine wave
>      decay. Quantitative
>      > measurement is tricky, but it's useful to compare known good coils
>      with unknown
>      > ones. Even a single shorted turn can dramatically change the
>      display pattern. It
>      > will also show up cracked ferrite cores.
>      >
>      > -John
>      >
>      > GBrown wrote:
>      >
>      > > I have seen an O-scope used to "RING" a coil. I cant find to
>      much on the net
>      > > about this. Anyone ever do this with success and if
>      so.......how?
>      > > Regards,
>      > > Gary...WZ1M
>      > >
>      >
>      > !
>      >
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>