Who makes their own OPT around here?

[BudP]

Nice work Wolfgang.... your hired!

Incidentally, here is a picture of what we have found to be the easiest, least expensive, most durable and least offensive style of rectangular/square winding form mounting arbor.

Materials are a carriage bolt in a convenient size, along with washer, wing nut set screw collar and two tapered metal pins or rolled pins. The form is made from pieces of oak glued together and sanded to size with a hole drilled through the center that fits the carriage bolt exactly.

The end plates are made from thin oak with the thick portion grain running across the grain of the slotted plate. The carriage bolt head is cut off and the assembly is mounted into the predrilled block of wood. A hole is drilled for the rolled or tapered pin through the block of wood and into the carriage bolt and a pin is driven in. Another pin hole is drilled through the outer end plate, into the block of wood and a second rolled pin is inserted into the block of wood.

These work better than metal arbors as the wood is softer to intruding fingers and the end plates don't flash as they revolve.

Bud

 

[ChrisA]

It can be done, naturally. But on the other hand, aside from price, there are good transformer firms out there and some will wind to your spec (and of those, some will make the specific transformer part of the catalog afterward, since the design work is just sitting there, and they have the equipment to wind anything on order).

Unless you are a serious garage-rat hobbyist, or really want to learn the art, the truth is you may as well work another 10 hours and throw the wages at the problem instead. Time isn't money, ...

Your argument also applies to building any audio amplifier. What is the point when you can buy an older classic amp off ebay?

I think there are two reasons to build rather than buy (1) you want something that is not available for sale or (2) you want to learn something.

For example, I have this idea that I combine a power supply filter choke and a single ended audio transformer on the SAME core. The large DC current in the choke would "buck" the DC current in the audio transformer and allow a MUCH smaller core with no gap. I foresee a few problems and the only way to know for sure is to try.

Another idea is "active shielding" I'm sure you all know how those Bose noise canceling headphones work. Can we sense an ambient magnetic field and servo it it zero? I'd like to try this to shield a sensitive microphone input transformer rather than making a triple wall mu-metal can.

I'm at a loss when it comes to finding materials like EI cores, insulating paper and end bells on retail size quantities.

 

[Yvesm]

. . .
For example, I have this idea that I combine a power supply filter choke and a single ended audio transformer on the SAME core. The large DC current in the choke would "buck" the DC current in the audio transformer and allow a MUCH smaller core with no gap. I foresee a few problems and the only way to know for sure is to try. . .

Hi,

This was common on many German made Radio consoles.
BTW, never tried myself.

Yves.

 

[TonyTecson]

sources in the states.....
http://www.thomas-skinner.com/pdf/laminations_general.pdf and Tempel

if i were in the states, this is what i will go for, nice c-cores and toroids, they sell in single quantities afaik...Silicon Steel C-Cores / Goss C-Cores for 60 Hz and 50/60 Hz Frequencies

Edcor sells Endbells....EDCOR - New Raw End Bells
hope they sell bobbins too....

this is another vendor....Bahrs Die & Stamping - Catalog

 

[BudP]

In addition you can contact Ram Sales here Transformer Components

A little wonky and pokey slow at times, but they have everything you might want and will sell and ship small quantities. Just go get a business license so they don't have to worry about taxation.

Bud

 

[TonyTecson]

Hey BudP, i wish i could go to the states to meet you......you have been very helpful to me....do you think RamSales will ship a pair of bobbins to Manila? i am looking for a pair of bobbins for 2inch centre leg with stack height of about 3 1/2 inches if such were available...

 

[BudP]

Maybe, but you would probably have to provide either a UPS or Fed Ex shipping PDF that Ram could use, on your account. You need to contact Dan at Ram Sales to inquire about their overseas shipping policies, if they even have any.

info@ramsales.net
Dan McGill

The parts would need to be shipped with a Harmonized Tariff's number. I use HS Tariff # 850431 as this is a catchall for transformers below 40 VA. Trying to find one for components or larger VA is a worthless enterprise. Parts should be claimed as manufacturer samples with a value of $10. This way they are not subject to VAT or other import duties and will sail through customs.

I did not see any 2" lamination materials in their catalog, but there is a wealth of 1 3/4" bobbins and mounting hardware. 1 3/4" lamination's may be easier to obtain too. I have attached a PDF of the relevant Ram Sales catalog page to drool over....

Bud

 

[BudP]

For example, I have this idea that I combine a power supply filter choke and a single ended audio transformer on the SAME core. The large DC current in the choke would "buck" the DC current in the audio transformer and allow a MUCH smaller core with no gap. I foresee a few problems and the only way to know for sure is to try.

Best to do this with a separate winding and some form of external splitter with variable control to allow exact DC current matching, or you must have a gap. Most E/I core can tolerate about 5 MA DC offset before beginning to oscillate into and out of saturation, beginning in the portion of the core that is carefully closed down, for minimum loss for AC flux. Small gaps really do not affect performance at low frequencies and for commercial core, have zero effect upon transformed AC signal above 400 Hz. So, if you had a 0.003" physical gap for drift (0.006" total gap in E/I core) and an adjustable DC offset current in a separate winding, I suspect you would be fine. You might also contemplate a distributed gap with opposing sectors of core.....

Bud