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Re: [Amps] transformer identification

Subject: Re: [Amps] transformer identification
From: Jim W7RY <>
Date: Tue, 15 Nov 2022 19:13:27 -0600
List-post: <>
Send me a copy direct ( so I can post on

73, Jim W7RY

On 11/15/2022 6:13 PM, Steve Bookout wrote:
Thanks for your input, Rob.

FYI, the picture was not taken with an audience in mind.  I just took it so I could remember the part number.

I think the AC input terminals were all mounted on a fiberglass terminal strip.

It is at a different location than where I'm currently.  I plan on being where the transformers location tomorrow.  I'll take some more pics, with some reference for scale.  I'll send them to anyone that would like to see them.  The pic I took yesterday, just about choked the reflector, so I won't post them here.

Steve, NR4M

On 11/15/2022 2:49 PM, Rob Atkinson wrote:
You have a transformer that appears to be on the small side but it's
hard to tell with nothing in the photo like a ruler to scale against.
The primary appears to be 1-4 which are not lugs but simply leads
coming out from the coil.   What I think is the secondary has two
solder posts, no CT so it is intended to be used with a FWB rectifier.
There's no lug insulation for h.v. so I suspect this is a low voltage
(< 1 KV) transformer.  It's odd to me that there's no center tap on
the secondary, but that could be a 115 v. primary.  However the lower
number leads are usually the primary windings.  This may be confusing
but I can't do more from a distance.  I'd use a VOM to measure the
coil resistance between the leads and see if a pair of the four
(probably 2 and 3) have no resistance between them.  Those two will be
the primary center tap.  Now you know the others are 1 and 4 and you
can put 20 or 30 v. AC across them and measure your v. on 5 and 6.
Start out with a meter like a VTVM set on 1.5 KV and come down as
necessary.  put everything on an insulated surface and keep all clip
leads and probe wires safely apart from each other and metal. set
everything up first before energizing the circuit so you can apply AC
and take a meter reading without touching anything.  Shut off AC and
change the meter scale and repeat until you get enough meter
deflection to take a measurement.    Remember that most DMMs max out
at 600 v. AC so using one can be risky to the meter.


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Thanks and 73, Jim W7RY
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