I didn't have time to get a transformer for a project which is a Christmas gift -- here's what I hooked up -- the wallwarts are beefy 20 watt types used in Zip Drives -- as external drives are all USB now they are collected in a box in the shop -- if you are going to test out these small transformers use a conventional light bulb in series to "current limit".
An externally hosted image should be here but it was not working when we last tested it.
Please tell me that you aren't really using a half-wave rectifier for the heater supply! Half-wave rectification puts a very nasty load on a transformer because it causes it to pass DC - which easily saturates the core.
it's a full wave rectifier -- just too lazy to draw in all the diodes -- the left hand wall wart was left "intact" with its diodes and capacitor --
So your putting 9v into the 2.5v worth of coil. Unless your getting out 400v+, your asking for drama.
You know better than that.
Oh wait, I see, it was 2 diode half bridge. Your only 100% above rated voltage.
You know better than that.
Oh wait, I see, it was 2 diode half bridge. Your only 100% above rated voltage.
I'll bet you really wish you hadn't started this thread...
Have you looked at the voltage waveform going into the HT voltage doubler? If it hasn't got flat tops then your transformer core isn't saturating.
Have you looked at the voltage waveform going into the HT voltage doubler? If it hasn't got flat tops then your transformer core isn't saturating.
no smoke yet -- there seems to be about a diode drop's worth of DC on the transformer coupling -- so there is some saturation going on -- this under load -- the temperature rise (can only measure the exterior of the transformer with a laboratory thermometer) is a few degrees C after 1/2 hr.
and the waveform (not pretty) between the two transformers (you can see the diode ringing.)
An externally hosted image should be here but it was not working when we last tested it.
and the waveform (not pretty) between the two transformers (you can see the diode ringing.)
An externally hosted image should be here but it was not working when we last tested it.
That's kind of like using valve float as a govenor on your lawn mower with the throtle wired wide open. 
But if it's not heating up, it may work for years without trouble. If you have a bunch of these transformers, just use 2. You'll put less hash on your mains.
But if it's not heating up, it may work for years without trouble. If you have a bunch of these transformers, just use 2. You'll put less hash on your mains.
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