Hello all,
I am currently building a very simple 6au6 preamplifier for a Wurlitzer electric piano using a toroidal transformer. The transformer comes with two primary windings of 115V. As I live in Europe, I connected two of the opposing windings together and hooked the remaining two to 220V. The color codes are yellow/white 115V/50-60Hz and orange/purple 115V/50-60Hz. Originally I tried putting the purple and yellow together but this gave no voltage output instead the transformer became very hot. It could have been on for no more than 20 seconds yet I still felt the warmth for some good time afterwards.
I returned to the unit this morning and placed 12V on the secondaries and found that the transformer would not work in 220V "mode" unless the white and orange wires were connected. Fair enough, but still the transformer is getting very warm after a short time of being on. Also, the 100mA fuse has never blown yet the 1k/5W resistor that is first in the power supply filter nearly burnt through in a matter of seconds!
The current draw is extremely small-- 300 mA for the heater and around 5mA for the anode. The transformer itself is rated for 2,5A for the heater and 100mA for the HT.
Did I somehow destroy the transformer by connecting the wrong wires on the primary? My understanding is that it wouldn't matter which of the two combinations I used. Either way, is heat generally a sign that the transformer is defective? I mean when there is so little current draw.
Thanks for any replies and sorry for the long post I am just trying to be as complete as possible...
I am currently building a very simple 6au6 preamplifier for a Wurlitzer electric piano using a toroidal transformer. The transformer comes with two primary windings of 115V. As I live in Europe, I connected two of the opposing windings together and hooked the remaining two to 220V. The color codes are yellow/white 115V/50-60Hz and orange/purple 115V/50-60Hz. Originally I tried putting the purple and yellow together but this gave no voltage output instead the transformer became very hot. It could have been on for no more than 20 seconds yet I still felt the warmth for some good time afterwards.
I returned to the unit this morning and placed 12V on the secondaries and found that the transformer would not work in 220V "mode" unless the white and orange wires were connected. Fair enough, but still the transformer is getting very warm after a short time of being on. Also, the 100mA fuse has never blown yet the 1k/5W resistor that is first in the power supply filter nearly burnt through in a matter of seconds!
The current draw is extremely small-- 300 mA for the heater and around 5mA for the anode. The transformer itself is rated for 2,5A for the heater and 100mA for the HT.
Did I somehow destroy the transformer by connecting the wrong wires on the primary? My understanding is that it wouldn't matter which of the two combinations I used. Either way, is heat generally a sign that the transformer is defective? I mean when there is so little current draw.
Thanks for any replies and sorry for the long post I am just trying to be as complete as possible...
It seems that you burned up the transformer by the incorrect connections to the primary. Did you use a fuse for that first test?
The proper pairing of the wires is required. You may need a new transformer, and you do need to review connection diagrams for such transformers. Some transformer manufacturers provide decent documentation. Always use a fuse before the primary, and for such tests make it a fast blowing type, 100 ma is fine. Don't guess about these connections, or have a good supply of fuses.
I just burned a fuse with such a test this morning (loose wire went astray), and I acquired more fuses today to continue testing. Fuses are cheaper than transformers.
The proper pairing of the wires is required. You may need a new transformer, and you do need to review connection diagrams for such transformers. Some transformer manufacturers provide decent documentation. Always use a fuse before the primary, and for such tests make it a fast blowing type, 100 ma is fine. Don't guess about these connections, or have a good supply of fuses.
I just burned a fuse with such a test this morning (loose wire went astray), and I acquired more fuses today to continue testing. Fuses are cheaper than transformers.
Do you have a transformer wiring diagram? It sounds to me like you still have yet to find the combination that puts the two primaries both in series and in phase.
Hi I had forgotten this thread for awhile. It turns out the transformer was faulty-- I had assumed something was wrong when I looked at the primary wires. they seemed to be mixed up. Sure enough, I wrote to the company and there was a problem. The new one works just fine.
Thanks for all the replies...
Thanks for all the replies...
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