Recently I have ordered custom-build R-core transformers (160VA and 500VA) from China factory along with chokes. It was too expensive after all because of high cost of shipment by air to Europe (only 500VA weighted over 5 kg), but I have nowhere to order them from Europe. I think its possible to order cores, bobbins and mounting kits separately, but does it makes any sense, taking into account shipping cost ???
Additionally, there is one more caveat. R-core transformers needs to be vacuum varnished after final assembly, and unless you order industrial-grade bunch, no one is likely to do so.
Additionally, there is one more caveat. R-core transformers needs to be vacuum varnished after final assembly, and unless you order industrial-grade bunch, no one is likely to do so.
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ok I see, maybe that is the reason they have not noticed my e-mail as I am using g-mail.
thanks for the link, I tried to visit but it couldn't open up for the moment, hopefully it will work soon.
Cheers Michael
Hi LinuksGuru,
so is the assumption your transformers are not vacuum varnished?
May you perhaps tell from which factory/shop you ordered your custom built R-core transformers, and how much did it cost?
Cheers Michael
You may not be able to strip windings safely if tranformer is vacuum varnished.
Hi LinuksGuru,
you have a point in that it might be quite difficult to strip of the windings from a ready made transformer, thanks for highlighting the issue.
Now, would you mind answer the other questions you already skimped on earlier and help in the spirit of diyAudio?
I'm sure many others are following this thread with interest and would like to learn from you, there is no reason to act counter-productive and pick on negative things in the first place when one can see it from the positive side as well so please be kind and provide something of benefit for all of us if you want so but if not please spare your time, thanks for your consensus!
Cheers Michael
Thanks for the links on Japanese transformer steel JBS🙂
Unwinding a vacuum impregnated tranny is not fun. Although impregnating one yourself should be relatively easy. There are some varnishes about that are available in reasonable quantities (not 50 gal).
An old fridge compressor and a pressure cooker is all thats needed. Make up some fittings so you can attach the suction side of the compressor to your "vacuum chamber". Some of the older compressors can get a real good vacuum. Just pretend you didnt let the CFCs out😀
A three way ball valve is ideal in the line because you can cycle it a few times between vac. and atmosphere, this helps drive out the bubbles of air in the windings.
The hard part is baking it. A box lined with rockwool and a couple of 100W bulbs does the trick over a day or two. Make sure you do it outside, its nasty.
Theres not much chance of doing it here at the moment its -18 🙂
Unwinding a vacuum impregnated tranny is not fun. Although impregnating one yourself should be relatively easy. There are some varnishes about that are available in reasonable quantities (not 50 gal).
An old fridge compressor and a pressure cooker is all thats needed. Make up some fittings so you can attach the suction side of the compressor to your "vacuum chamber". Some of the older compressors can get a real good vacuum. Just pretend you didnt let the CFCs out😀
A three way ball valve is ideal in the line because you can cycle it a few times between vac. and atmosphere, this helps drive out the bubbles of air in the windings.
The hard part is baking it. A box lined with rockwool and a couple of 100W bulbs does the trick over a day or two. Make sure you do it outside, its nasty.
Theres not much chance of doing it here at the moment its -18 🙂
Hi Matt,
you are a resourceful man! 🙂
Actually I have a fridge compressor (which was disposed on CFC in correct way), it was meant to use as vacuum pump for making parts from carbon fibre fabric but that project went down but I saved the compressor as it's in good condition and I thought so it would come to good use some day! 😀
I think the transformer have to be dipped along the bobbin axis and let the varnish cover up to about 98% so one end is free for the air to come out as I thought the air bubbles trapped inside the windings would otherwise have difficult to come out if the transformer is fully drained into the varnish.
A bulb is very good for a temporary heat chamber, for one company I worked for in the past the guys used a typical Styrofoam cool-box for food they covered inside with aluminium foil and a bulb as heat chamber, but it utilised a thermo relay which had 10 degrees hysteresis so I rebuilt it and made one of a string of diodes and a comparator IC and got 0.2 degrees hysteresis, so nothing is impossible.
EDIT: Forgot to tell, but I finally got a reply from Kitamura Kiden in Japan, unfortunately they don't sell to private persons and can not help with contact information. The retail company they refer to on their homepage, http://www.pnxcorp.co.jp/ doesn't sell outside Japan, quite funny because the information is written In English...
Cheers Michael
you are a resourceful man! 🙂
Actually I have a fridge compressor (which was disposed on CFC in correct way), it was meant to use as vacuum pump for making parts from carbon fibre fabric but that project went down but I saved the compressor as it's in good condition and I thought so it would come to good use some day! 😀
I think the transformer have to be dipped along the bobbin axis and let the varnish cover up to about 98% so one end is free for the air to come out as I thought the air bubbles trapped inside the windings would otherwise have difficult to come out if the transformer is fully drained into the varnish.
A bulb is very good for a temporary heat chamber, for one company I worked for in the past the guys used a typical Styrofoam cool-box for food they covered inside with aluminium foil and a bulb as heat chamber, but it utilised a thermo relay which had 10 degrees hysteresis so I rebuilt it and made one of a string of diodes and a comparator IC and got 0.2 degrees hysteresis, so nothing is impossible.
EDIT: Forgot to tell, but I finally got a reply from Kitamura Kiden in Japan, unfortunately they don't sell to private persons and can not help with contact information. The retail company they refer to on their homepage, http://www.pnxcorp.co.jp/ doesn't sell outside Japan, quite funny because the information is written In English...
Cheers Michael
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