[Boatanchors] LS-183

[D C _Mac_ Macdonald]

I have an old (1940s) Marx toy train transformer that I use to put 12VAC on the primary.

Yes, I've had it since I was about 8 years old!

Then I just multiply output voltages by 10 to get an unloaded output of a transformer in question.

It's unlikely that that output would be more than 200V which is "reasonably" safe for klutz folks.


* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *
* (Since 30 Nov 53) *
* Oklahoma City, OK *
* USAF, Ret'd 61-81 *
** FAA, Ret'd 94-10 *
* * * * * * * * * * *





________________________________
From: Boatanchors <boatanchors-bounces at mailman.qth.net> on behalf of Michael D. Harmon <mharmon at att.net>
Sent: Wednesday, November 30, 2016 22:16
To: Boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] LS-183

Hi Ernie,

I know it's sort of a pain, but when I am trying to map out an unknown
power transformer, I use the same essential technique as Alex
recommended, with the following addition:

I start from a reference, say the first lug, and measure the DC
resistance between that lug and every other lug on the transformer. Then
I move the common meter lead to the second lug and repeat the process
for all lugs on the transformer.  I keep doing this until I've measured
the DC resistance between every lug and every other lug.  Now I have a
list of resistances, and it's relatively easy to figure which lugs are
attached to each winding.  After that, you should be able to identify
the taps on each winding.  Just keep in mind that resistances of say,
less than 5 ohms are probably filament windings, 5-20 ohms are probably
primaries, and anything much higher than that is probably a plate (or
bias) winding.

Once you have a ball-park idea as to which windings are what, hook up a
dim-bulb tester in series with the suspected primary winding. Start from
zero on a Variac and slowly advance the voltage a few volts at a time,
watching the other windings with an AC voltmeter. You should be able to
get a relative idea as to the ratio of the input and output voltages.
If you accidentally apply power to a filament winding (or the winding
has a shorted turn), the dim-bulb tester should keep you from doing any
damage - the bulb will just glow brightly.

It's a little bit time consuming, but it has always worked well for me.

Mike, WB0LDJ
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