Notes on power transformers for sale.

In 2008, obtained the hundreds of power and output
transformers, and filter chokes
from a fellow who needed to move house to an apartment where there was little
storage room. I have spare room here so he and I agreed I could store them and
advertize them for sale, and share the proceeds. Total weight of stocks were about
1 tonne, and perhaps I have sold about 50Kg total.

It is a fact that although I have hundreds of power and output transformers and chokes
in my stocks, most are widely different to each other, and the chance that something
I have might suit a given project some DIY person says he wants is remote. And after
supplying about 25 items from my stocks of hundreds during the 4 years to about 6
customers, only 1 has completed work on an audio amp project.

So I will NOT spend a pile of time sorting out what you want unless you can convince
me you are serious about building something.


You need to tell me about your project, and give all details of schematic of the amp
and PSU.
Please try to send me a schematic which is well drawn and less than 200kB in file
size, .pdf or .gif, .jpg,
Or send me a link to a URL.
Please email a link to a website which has a schematic and description
of your project.

I can recommend the choice of schematics i have elsewhere at
this website.

Perhaps you'd like to study my informative web pages at

powersupplies.htm

powertranschokes.htm


I would always like to think that after you have successfully built a
preamp to get
some practice at building tube operated electronics,
perhaps you may become
experienced enough to design and
build power amp.

For those unable to fully design any amp, I would be able to select a
compatible
set of parts including a power transformer, output transformer
and filter choke
and probably be able to supply a schematic suitable
for almost any output
tubes you can think of between a tiny 6AQ5
up to an 833.

Should someone wish to have me draw up a schematic and design s
omething
special and offer information support as construction
progresses, there may
be a moderate cost involved. If a DIYer
purchases a complete set of iron
components for a power amp I
usually can offer a free suitable schematic
to best suit their purchase.  


At times some DIYers have obtained the parts they need from myself
or another
supplier, and then decide they don't have available time to
construct anything,
so they ask me to do it for them. I'm usually
booked solid for many months
with orders so they would have to wait.
DIYers MUST REALIZE considerable
time must be spent on hobbies
if a good result or any result is to be had,
so don't ask me to care about
your DIYer project if you are so bone lazy
you can't get busy after
working hours instead of playing computer games,
watching TV and
doing 101 other trivial pursuits. Support I maybe asked to
give can be
expensive depending on what sort of workmanship a hobbyist
has achieved before he hands his work to me to inspect, repair, adjust, modify.
I suggest all DIY hobbyists complete all work and get their amplifier projects
basically operational before bringing it to me for any final
adjustments which
might include critical damping network adjustment
where NFB is applied,
because some years of experience are needed
to get this right.

Where I have had someone keen who has purchased a set of iron-wound
parts, I have been very helpful with schematics and advice.
 
I do not supply full kits of parts for amplifiers. DIYers must be able to work out
fine details, and source all minor parts such as tubes, diodes,
resistors,
capacitors, solder, hookup wire, terminals, switches, chassis,
LEDs, SCRs,
BJTs, nuts, bolts, screws, tag strips or anything else.
There are plenty of good
suppliers online for tubes and for small parts and
I suggest
http://www.wescomponents.com.au and http://www.evatco.com.au

Usually DIYers realize that if I were to supply minor parts, they would have to
pay much more for them for me to spend time dealing with an
order, working
out the order, and supplying in small quantities.


About the transformers for sale......

Most transformers have GOSS double C-cores, formerly made by
AEM in Sth
Australia. These low loss cores run with a low rise in
operational temperature.
After inspecting each transformer type and measuring wire gauges where
possible I have given current ratings for each secondary winding based
on 3Amps per square millimetre of copper section area, eg, for 1.0mm copper
dia wire the rating is 2.36 Amps.


Most transformers have carefully layer wound wire with at least
0.15mm thick
Nomex or polyester insulation between every layer
of wire. There is a bobbin
with 3mm base wall thickness with ends of wire
layers all kept back 3mm
from the edge of the insulation to maximize
creepage distance.

Precautions.....

Buyers should have slow blow fuses to all primary and secondary windings.
Fuse values should be no more than 2 twice the expected operational
maximum RMS current.
So if a primary has 1 Amp rms maximum of input current while charging
capacitors, the mains fuse should be a slow blow 2 Amp type, or just above the
value where there would be occasional nuisance fuse
blowings.
 
There are NO thermal fuses inside the windings of these transformers.


Because I have no control over how anyone might use the transformers
being
offered, I cannot offer a warranty included if you do not construct
your amplifier
to high standards of safety and protection against bias
failure or any other fault.
There are schematics elsewhere at this website for active protection against
bias failure and excessive cathode currents.
All tube amps should have such
protection fitted!!!


Some transformers with E&I laminations were made in the 1960s
by A&R or
Ferguson and have been in use in other equipment but
are still in excellent
condition.


Buyers should carefully design their amp schematics with regard
for anode
supply voltages and anode load values and allow the B+
winding to cope
with at least 33% more current delivery than
required at the idle condition.
They should allow for some flexibility for the anode supply voltage of say
+20% and -5% before finalizing their design.
It is easier to use a series resistance in the B+ circuit to the OPT input to
slightly reduce the B+ to enable the right Iadc for class A
working with the
load wanted.

It is impossible to increase the B+ voltage easily if the HT winding has a
voltage which was too low for the project.
The best outcome for the hobbyist
is to design the amplifier and
its PSU and power tranny around the output
transformers available,
rather than insist that the amplifier conform to yet
another
configuration for which it is impossible to find a perfectly suitable
output transformer which will always be harder to find
than a suitable power
transformer. Buyers should have the iron
wound parts in their possession
before proceeding to make a chassis
or to purchase one so as to optimally
arrange the parts for
spacious and well proportioned layout.

Mains Voltages....

All power transformers have nominal 240V primaries to suit
Australian buyers,
or where mains voltages are between 220V
and 250V.
The secondary voltages stated are nominal working voltages with 240V

applied to the primary.
The B+ anode supply voltages are calculated at 1.35 x Vac and for
working
Idc and for capacitor input filters. Bias windings can give
Vdc = 1.35 x Vac,
or 2.7 x Vac depending on rectifiers being single
silicon diode, silicon diode
bridge, or doubler configuration.

For those wanting to use tube rectifiers, the B+ Vdc at the reservoir
cap will
be between about 1.0 and 1.2 x Vrms of HT winding,
with the B+ being
highest factor used where Idc is small, as it
may be for a preamp.

For choke input filters,

the B+ Vdc at the cap after the choke will be approximately 0.8 x Vrms at the
working Idc, and only if the choke winding resistance is low.


The input VA rating is that of the input winding only,
and VA = Input Vrms x Irms.
This input VA rating will be equal to the sum of all VA ratings for all windings
plus 10% winding and core heat losses. A user may find
that he can extract
more current from a HT winding than the
VA rating indicates but this means
he must then extract less current
from other windings to keep the total VA
under the transformer
input VA rating.

Some HT windings for B+ have a higher VA rating than required
for idle
conditions because one must allow for temporary higher
anode currents
because of class AB working and and occasional
tube bias faults.
In general, the core VA rating for C-cores is higher than the copper winding VA.
The C-cores have a larger ratio between winding window area and the iron centre
leg area when compared to wasteless pattern E&I
laminations.

Thus winding losses in C-core transformers are lower than when using standard
wasteless pattern E&I laminations for the same VA.
The permeability of GOSS
C-cores is higher than for non oriented
Si Fe cores.
Heat losses for GOSS is often negligible because the iron permeability is very high,
usually above 7,000. GOSS Toroidal cores have the highest
permeability because
there are no joins in the sheet metal strip used to
wind the spiral core, so toroidal
cores run coolest of all, and this
is needed because the core is suspended within
the many insulated
layers of wire and core heat cannot escape easily.

The C-cored transformers will be supplied with mounting brackets
attached, and
all supplied with full information.


For sale power transformers


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