StephenTetorka@cs.com wrote:
> Hi guys:
>
> I have a vintage filament xmfr.
>
> Voltages are a little high without load...and making allowance for 120 in
> place of 110 ...and there is evidence of repair and sign of past leaking
> resin.
>
> What the 'recommended' way to work up a full load - 10 Amps - to see if this
> bugger can handle it?
>
> Tnx,
> Steve
> WA2TAK
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>
Can I make a simple suggestion - you pick a more appropriate title. Why
not "testing filament transformer" or something like that? Then people
will not have to read things they know nothing about. Archives can be
searched in a sensible manner etc.
Personally, given its condition I would try to get another and throw it.
(At this point you really don't like me!!)
Now to answer your question.
The best test is going to be to find what the *maximum* heater current
will be. That will not be the normal one, but worst case - i.e. look at
the data sheet. Then get a resistor and load it up.
R = Volts/current.
Power = voltage * current.
Given the power, which is likely to be 50-100W, it will need cooling. A
100W resistor will need a heat sink. But I'm pretty sure a bucket of
water would do fine. I have not tested it I must admit, but unless it
boils around the resistor, which is most unlikely at that power, I think
that would be fine. The resistor would not get too hot.
If you have a decent heat sink to screw it to, then all the better. But
for test purposes only, water will do. At that resistance, which will
only be an Ohm or so, you need to be careful about lead resistance, so
take that into account. Short the DVM leads and subtract whatever you
get from the resistance you measure.
Water is a bit conductive, but it will have negligable effect on a 1 Ohm
ore so resistor. If it was 100k or more, then perhaps so.
If you have a decent 4-wire meter, then it will be much more accurate,
but I doubt you have that.
But personally I would throw the transformer. If it shows sign of repair
and leaking resin, I suspect it has been overloaded at some point. You
have no idea how much damage it has done. It might work today, but next
month it might be another story. If heater current gets removed from a
tube, it is unlikely to do it a lot of good if running at full output.
--
David Kirkby,
G8WRB
Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/
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