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Bob Bob is offline
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Default Kenyon transformer S-510426

I have a Kenyon transformer that I believe is an audio transformer,
model S-510426. Can anyone verify the specs or usage for this
transformer?
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[email protected] arthrnyork@webtv.net is offline
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Default Kenyon transformer S-510426

On Oct 23, 7:42*am, Bob wrote:
I have a Kenyon transformer that I believe is an audio transformer,
model S-510426. Can anyone verify the specs or usage for this
transformer?


May be a power transformer,but not 100% sure. What color wires it does
it have ?
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Bret L Bret L is offline
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Default Kenyon transformer S-510426

Have you phased it out to find the windings and ratios? A little
common sense here can usually answer these question.

If it has a winding that when energized at 110-120 vac gives some
rational voltages on the secondaries such as a HT winding and 6.3 0r
2.5, 5 volts, you probably have a power transformer.

You see a lot of single voltage filament transformers, with or
without center taps on secondaries, that are Kenyons. Also modulation
transformers. Those have multiple taps on primary and secondary
usually, the primary being center tapped.

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Patrick Turner Patrick Turner is offline
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Default Kenyon transformer S-510426

On Oct 29, 12:30*am, Bret L wrote:
*Have you phased it out to find the windings and ratios? *A little
common sense here can usually answer these question.

*If it has a winding that when energized at 110-120 vac gives some
rational voltages on the secondaries such as a HT winding and 6.3 0r
2.5, 5 volts, you probably have a power transformer.

*You see a lot of single voltage filament transformers, with or
without center taps on secondaries, that are Kenyons. Also modulation
transformers. *Those have multiple taps on primary and secondary
usually, the primary being center tapped.


The very first thing we need to do to identify windings is to measure
the resistance of all windings and identify the leads or connections
into a winding diagram in out work book and in a sensible manner.

Always begin Vac testing using a LOW VOLTAGE, say from the 5V winding
of another mains transformer. There should be a series 4R7 resistance
be used in series between the low voltage initial test signal and any
coil beig tested. If there is a shorted turn in the transformer
because it has become faulty and unusable, then you want the 4R7 to
get hot rather than anything else. Even if you have 5Vac into some
identified winding and it is a low voltage type then there may be some
other winding meant for much higher voltage, say 300Vac, and that CAN
BE VERY DANGEROUS unless one realizes that ****ing around with
transformers can easily kill you.

But with only 5Vac across one of many windings, one can measure and
WRITE DOWN the the voltages on all other windings.
This allows you to calculate the voltage ratios fairly safely without
anything going to too high a voltage or likely to make smoke.

If one ever finds a transformer which has unknown voltages because
there is no information written on any cover or attatched plate, then
after identifying windings their resistances and taps, one could
suspect it is a mains type and establish the VA rating from the old
formula, VA = (A x 4.4) squared.

So say the core centre leg which goes through the windings is say 2" x
1.5" then A = 3 sq inches.
4.4 is a constant for all equations. So for such a tranny VA = ( 3 x
4.4 ) squared = 174 Watts.

This means that if it is a mains tranny, then one winding will have
input voltage x input current = 174W when all secondaries are loaded
by their design loads. If Mains = 115Vac, then Iac in = VA / V = 174 /
115 = 1.51 amps.

Also, one would say the load looking into a primary = V / I = 115 /
1.51 = 76 ohms.
If there is a 115V mains winding, one might assume the designer has
made its resistance equal to 1/20 of the input load, ie, about 76 / 20
= 3.8 ohms. If there is 1.5A current, power in heat liberated by such
a winding is 8.6W.

So once a winding with Rw = about 3.8 ohms has been found, it may be
connected to a 115V supply VIA A 100 RESISTANCE RATED AT 10W so that
in case the winding was not meant for 115V, one does not cook the
winding, but cooks a cheap resistance instead.
Once the 115V is supplied via a 100R and **without any sec loads**
then one can measure the voltage across the coil being examined and
the 100 ohms. Professionals would use a Variac and oscilloscope to do
all this so they can monitor distortion caused by the iron
saturation.

But the DIY person armed with no more than a DMM can still find out
lots about the tranny. With 115V and 100R the voltage across the 100R
should be fairly small compared to voltage across the coil which
indicates the inductance of the coil is much higher than the value of
the 100R.

Assume the non professional has no ideas about measuring field
strength. He might assume the designer made the transformer to follow
design rules which end up giving the primary coil an inductance which
has a reactance in ohms at 60Hz of about 10 x input load value. In
this example, perhaps that might be 10 x 76 ohms = 760 ohms.
This means that the primary inductance = 760 / ( 2 x pye x 60Hz ) =
2Henrys.
LR theory suggests than where inductive reactance XL R by a factor
of more than about 5 then current in R + L = approx V / XL = 115 / 760
= 0.15 amps ac.

We should understand from the outset what sort of voltages we might
expect after considering the core size and winding resistances.

The expected voltage across the 100R might be about I x R = 0.15 x 100
= 15Vac.
This tells us magnetizing VA = 115 x 0.15 = 17.2, except that the
figure is not actually in Watts because power is never liberated in a
pure inductance, but nevertheless some will be in the core.

So if we did observe 15Vac across the 100R in this example then
probably we do have a mains primary winding.

If voltages on other windings give say 6Vac, 5Vac, 300Vac, or 600Vac
with a CT, then it looks like a mains transformer is present.
But suppose there seems to be just two windings, with one having Rw
1 ohm, and the other is a CT winding with Rw = 300ohms, and this has a
CT, and the voltage ratio is say 20 : 1, or 115Vac : 5.75Vac then it
is likely one has a PP OPT meant for matching a pair of tubes in PP
with primary RL = 6,000 ohms and secondary meant for 15 ohms.
This because the Rw of a primary of many OPTs is made to be 5% of the
primary load.
The voltage ratio in this example might be 20:1, so impedance ratio =
400:1, so if Rw primary = 300 ohms, then its load is 6,000 ohms and
the other winding = 6,000 / 400 = 15 ohms.
If there are terminals or leads for taps along the low voltage winding
so that one reads 4Vac and 2.87Vac from one end of the winding then
these taps are likely to be for 8 and 4 ohms.

When using a DMM to measure winding resistances it will be found that
many OPT primary windings have so much inductance it prevents the
winding resistance to be measured. The meter just flashes aimlessly at
you. Usually this means the tranny is not a mains type.
So strap a wire across some other winding, and then the inductance
effects become shunted and Rw can be measured well with DMM.

That is enough to digest right now. There are other things one might
find out, like frequency response. But they can wait.

Patrick Turner.

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Big Bad Bob Big Bad Bob is offline
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Default Kenyon transformer S-510426

Patrick Turner wrote:
CAN BE VERY DANGEROUS unless one realizes that ****ing around
with transformers can easily kill you.


testing continuity with a battery and a flashlight bulb, using fingers to
hold wires on the battery, can be similarly 'energizing'. Anyone say
'signal generator and/or o-scope' ? A lot of scopes (or older ones, anyway)
have a calibrated voltage output (like 1V p-p) with built-in overload
protection that you could theoretically apply to ANY winding, then use the
scope to (carefully) measure the signal at the various points, with the
assumption that the scope input has proper overload protection as well,
which it should. 1V p-p on a primary for an OT might give you 10s of
millivolts on the secondary but that's ok for a decent scope. You'll get
really accurate measurements, too.




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[email protected] arthrnyork@webtv.net is offline
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Default Kenyon transformer S-510426

On Nov 3, 5:01*am, Big Bad Bob BigBadBob-at-mrp3-
wrote:
Patrick Turner wrote:
CAN BE VERY DANGEROUS unless one realizes that ****ing around
with transformers can easily kill you.


testing continuity with a battery and a flashlight bulb, using fingers to
hold wires on the battery, can be similarly 'energizing'. *Anyone say
'signal generator and/or o-scope' ? *A lot of scopes (or older ones, anyway)
have a calibrated voltage output (like 1V p-p) with built-in overload
protection that you could theoretically apply to ANY winding, then use the
scope to (carefully) measure the signal at the various points, with the
assumption that the scope input has proper overload protection as well,
which it should. *1V p-p on a primary for an OT might give you 10s of
millivolts on the secondary but that's ok for a decent scope. *You'll get
really accurate measurements, too.


The 1v p-p calibration is usually a square-wave . Not every
transformer may pass it properly and may lead to erroneous results. A
simple 12 to 24 VAC adapter (not critical) are safe enough to do
nearly any all testing as far as transformers go.
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