[ARC5] Slightly OT: Transformers

[J. Forster]

Hi,

I'm replying on-list because they are generalized queries.

A few hints:

Many transformers are purpose uilt, and only have 'house numbers'. Specs
may well be long lost, or never existed outside a comnpany's engineering
dept.

There is a standard EIA color code for transformer leads. Google should be
your friend. To be safe, you should Ohm it out to be sure it followed the
color code. If it does, move to the next step:

Hook the primary to the line (preferably through a Variac and isolation
transformer) with a standard 120V incandescent lamp in series. A 25-40W is
about right for small transformers, a 100W for larger ones.

Apply power. the lamp should glow dimly to not at all. Measure the
secondary voltages CAREFULLY.

Apply power and then touch the meter leads to the wires. If you switch the
AC off w/ the VOM connected, the inductive kick can blow the meter.

You can roughly estimate the power rating by weighing the thing. At 60 Hz,
for conventional EI transformers, it's about 40 W/pound.

Good luck,

-John

==========================


> Greetings all,
>
> I have some questions about transformers and this seems to be the only
> group I'm in now that deals with tube rigs.  I hope you don't mind
> elmering
> me a bit by answering a few questions.  I mention slightly off topic
> because one day (hopefully soon) I'll start building a power supply to use
> with my ARC 5 rigs, but for now, I just want to be able to power some
> basic
> homebrew tube transmitters.
>
> So, my questions go along the lines of...  I have several transformers
> that
> have followed me home from hamfests or someone has given me.  But most are
> not labeled in any fashion as to what they are rated for.  As stated
> above,
> I'd like to build a small power supply that can run some homebrew tube
> rigs.  I might actually use some of the thousands of tubes that followed
> me
> home from hamfests instead of leaving them piled in boxes with no use.
> I've tried googling any number or marking on the transformers trying to
> find a manufacturer or specifications and haven't had any luck.  How can I
> test these safely as to not hurt myself or the transformer so that I find
> out at least the voltages I should expect out of them?  Right now, I'm not
> too concerned about finding how many amps they will provide as much as now
> much voltage is on the end of the wire.  The number of amps question will
> come soon though.
>
> Currently I have a transformer on my bench that has the following markings
> 110v004h82
> 352052
>
> It appears to have 3 windings.  A black set (I presume is the primary), a
> red set with CT, and a green set with CT.
>
> I'm kind of skittish at just applying 110v to the black wires and seeing
> what the others have for voltages.  So, I figure why not ask some hams
> that
> might have a better clue than me.
>
> Please respond to me off the list as I don't want to waste too much of the
> list's bandwidth on something that might be determined as an elementary
> question that we all should know.  I'll be quick to say that I'm a very
> much at an elementary stage on using HV and know enough to ask questions
> before just trying things.
>
> Thank you for the bandwidth and Happy Thanksgiving to all
>
> 73,
> Eric
> k8ohz
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