Re: Ping Patrick (was Re: FA: Pair New Heyboer 40W SE Output Transformers

In article <C381AE63.A294D%jono_1@xxxxxxxxxxxxx>,
Jon Yaeger <jono_1@xxxxxxxxxxxxx> wrote:

I am in the planning stages of another funky amplifier project, these
transformers look like they might just be weird enough to be at home in
the project. Would it be possible for you to make some simple
measurements on the transformer? I am curious what the end to end DC
resistance of the secondary is, as well as what the DC resistance of the
primary is. Also the primary to the entire secondary turns ratio, which
can be measured by applying 6.3 VAC @ 60 Hz across the entire secondary
winding and measuring the voltage that appears on the primary, along
with the exact voltage applied to the secondary.

John,

My digital VOM is notoriously unreliable in the very low ohms range, and so
I used an ESR meter to measure the resistance of the secondary, end-to-end,
from the common lead to the 16 ohm lead.

I measured the resistance of the primary with the digital VOM, because it
was too high a resistance for the ESR meter . . . . ;-)

Both the ESR and VOM were spot-on measuring a precision 10 ohm resistor, so
I feel pretty good about the overall and relative accuracy.

I measured the input (secondary) voltage under load, and the resultant
primary voltage with no load.

Here are the results:

Primary resistance: 47.2 ohms

Secondary resistance: 10.0 ohms
(end-to-end)

Input (secondary voltage) 6.32 VAC

Output (primary voltage) 72.60 VAC

Voltage / turns ratio: 11.5


I'm curious what your interpretation of this data might be.

I've got the jig still set up if you have other questions.

Hi Jon,

Thanks for making the measurements for me. If your measurements are
accurate, then my interpretation of this data is that the best thing to
do with this transformer is to "bin" it. The turns ratio, ignoring the
effects of winding resistance, implies an end to end secondary impedance
of approximately 18.95 Ohms. A secondary DC resistance 10.0 Ohms is
totally unreasonable, nearly an order of magnitude greater than what you
would like to see. Given the turns ratio and the DC resistances, it
appears that the secondary is wound from finer wire than the primary,
which is sort of backwards, although the "spec." *** implied that the
secondary was wound of fine wire. One has to really wonder what this
transformer was originally designed for, certainly not driving a
loudspeaker. The only additional test I would make would be to verify
that the secondary winding does not use much heavier wire at one end
than the other which might change my interpretation of the data. I
would do this by again applying 6.3 volts across the full secondary and
measuring the voltage at each tap to find the tap closest to the center
which would have approximately 3.15 volts on it. I would then measure
the DC resistance between this tap and each end of the secondary
winding. If one of these resistances was say 0.5 Ohms or less, then the
transformer could have some use other than a trip to the "bin".


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/
.

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