Transformer Quality
Technology advances, but why do we perceive that performance
or quality over price ratio has dropped drastically? We could buy really good
quality stuff in the past with just little money but nowadays quality comes
with a super high premium.
In this article, we are going to talk about transformer
quality. Transformer quality is deteriorating everyday as we speak. For the
sake of earning more return, higher ROI, high volume manufacturing, quality is
compromised by some of the manufacturers. It may look OK on the outside, but
it’s just crap in the inside. Or worse is such horrors are hidden behind a
nicely portrayed designer chassis. Do not consider potted transformer to be
premium!
Many has suffered, many has been conned by such nicely
decorated exteriors. We do not know what’s well hidden inside (transformer
potting) until something goes wrong! We’ve suffered before from a few famous
local winders / distributors in our country, not just from overseas – you know
where. What was sold to us are just plain junk that is LOW-FI, not HIFI. Now we
take no chances. We only get from reliable sources. We constantly look for new
vendors with quality and reasonable price offerings.
In addition, potted transformers are bad in dissipating heat
and therefore cause the reliability and longevity to be shortened extensively. Transformers
love to radiate heat as much as possible to cool the wires and core down to
prevent premature breakdown or disintegration of the material over time. We would
not recommend potted transformers.
We’ve seen puny little transformer hidden inside a huge
metal can. When you knock at the can, you can hear echo coming out. Now that’s
really bad news for those that bought such transformers. Some cases that do not
sound hollow, they might be filled with (heavy) filler too, don’t be so happy
first! For some that already has crappy outlook, please expect the internal
(where you cannot see) to be much worse since they already do not care
externally, why would they care internally?
Quality repair is getting rare too. Repair services are
scarce nowadays, especially good repair technicians. Repairing potted
transformers will be expensive too since removing them from the cases / pots
will be very difficult, not to mention cleaning up the potting compound will be
very messy / dirty / difficult. On top of that, repaired transformer needs to
fit the original pot! Proper transformer with the right specifications for the
job might not fit the original enclosure as they’re usually bigger in size! Therefore,
repairing such transformers needs skills and experience, and such repair cost
will be high due to all the work involved. Making a brand new transformer will
be easier and cheaper! Some will just ask you to buy the original transformer
from the OEM that costs a bomb!
The returns will be huge for those heartless crooked manufacturers
since they pay lesser for the cores, wires, time due to poor workmanship, and
etc. You save on buying cheaper transformers but you lose big time on quality,
reliability and outcome. Trust me; there are really such conmen out there!
Now, do you want to end up in such situation with inferior
transformer quality? We definitely don’t. We’ve paid too much ‘tuition fees’
and we’ve promised ourselves to suffer no more.
Others usually use H-core that is ~0.5mm thick, which is not
as good as the Z11 core. So what you should do? Go learn on how to
differentiate the difference between the core materials. Usually Z11 core is
thinner and greyish matte (non-shiny) in finishing. If it is potted, good luck
and only buy from reputable dealers. Do
be careful even if does not look shiny. It might just be a smart and good paint
“con” job. If it feels too hot, it probably is inferior in quality.
Power transformers for tube amplifiers will be harder to
make due to the multiple taps for high voltages, low voltages, filament
voltages, bias voltages and etc. High voltages require more windings too for
voltage step-up. For such transformers with many windings, insulation job must
be treated with care, to isolate the high and low voltage windings, and also
the tap outs need proper care to avoid short circuits. These are all hard work!
Such complicated transformers will be prone to mechanical
vibration or hum if it is not designed properly. Some manufacturers used a lot
of potting compound or glue to hide such design issues or defects as a cover
up. These transformers will not last very long. Vibrating transformers will
cause the wire insulation to weaken faster and cause shorts. Only properly
designed high transformer quality will not have such problems and will last
much longer than the rest.
Real scenario: potted transformer is sent for repair but the
original core is replaced with another on-the-shelf transformer instead of
being repaired. So, when you send for repair, do look for signs that your
transformer is being repaired or replaced.
- Weight difference – too light?
- Duration of repair – too fast?
- Price – too cheap?
The value is all gone when the original core is lost. You
will not get back what you had before the repair.
There’s another case that the power transformer we received
for repair has not gone through varnish soaking at all! Such kinds of
transformers are unsafe. Do not use them! You can observe it easily. Just see
if there is any varnish residue on the exterior or at the windings. If it looks
like there is no varnish at all, don’t buy them! Varnish will fill up all the
air pockets and protect the power transformer from moist and also strengthen
the insulation.
Are toroid transformers always being better than EI core?
Not necessary. Some toroid transformer winders will just wind the transformers
from start till the end with a single wire, and without having insulation
layers, coupled with potting material, will cause the transformer to overheat
or short circuited in a short time. Use with precaution!
Important tip: if your transformer core looks bright and
shiny, don’t be happy. Usually these are the low grade cores. Although they
look nice, they waste a lot of energy.
- Poor method of tapping out from the windings – wrong use of insulation methods will just short out the taps very fast. Proper calculation is needed to determine the insulation + thermal strength needed for each and every case. Some just apply the same standard for all the transformers they make, for high or low voltages, which is just darn wrong.
- Misaligned core, shiny core could mean low quality core that has very high loss = burns electricity even if there is no load, beware!
- If it looks funny, then trust your instinct, it probably is, do not use or buy! Such transformers probably do not contain good workmanship and therefore the quality or outcome will not be good. Reliability will be questionable too.
Nowadays we found that some transformers are using unknown paper
insulated with insulation tape to replace imported Kraft paper dedicated for
transformer use. Such insulation strength will not be sufficient, especially
for high voltage tube amplifier applications. We will not do so. Such build
will malfunction in a very short period of time.
Some winders cut corner buy using a smaller core, lesser
core lamination, lower quality / grade than needed. Perhaps the core prices
has gone so much expensive that for them to make “MORE” money, they’ve to go to
such extent. Such method will make the transformer very hot and will age
faster. Or they might mix core materials together to appear as high quality
cores. One can only know if they dismantle the cores – which one rarely does
until it is sent for repair. Who loses? You, the consumer! Ethical
manufacturers are getting lesser and lesser as we speak.
Using plastic film as inter-winding insulation – no! It saves
a lot of cost and is very easy to make. We do not use plastic films. We use the
correct insulation paper material for inter-winding insulation for utmost safety.
Some customers may complain that why our transformers are
more expensive than the generic transformers in the marketing. We wish to
explain here that out transformers are all made with the highest standards and
the quality is reflected in the price. We’re still very competitively priced
compared to the famous European or American brands. You are paying for the
value – reliability, longevity and sound quality.
If you have suffered the same fate of poor transformer quality, please feedback and let us know where it comes from and what happened. We need to educate our fellow audiophiles and DIYphiles on such vendors.
Some sharing if pictures below:
Poor fixing for output taps - no insulation too! |
Badly wound high voltage winding. |
Badly wound low voltage high current winding. |
Burn insulation layer - insulation uses normal tape! |
Burnt Kraft paper. |
Burnt transformer. |
Burnt low voltage high current winding |
Burnt transformer winding |
Poor core stacking |
Misaligned core stacking |
Poor core stacking - misaligned too! |
Misaligned core stacking |
Misaligned core stacking |
Badly done output taps. |
Output taps without proper fixing - short circuit and arcing risk! |
Poor output tap |
No insulation for output tap, short circuit risk! |
Toast for your peace of mind!
J&K Audio Design
17/12/2013
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