Transformer regulation question

Tube DIY Asylum

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I'm having a run of 15VA heater transformers wound by a new supplier and for such a simple device , it's causing me to doubt my own sanity . Having trouble trying to get the winder to understand that I want the output voltage to be 6.3V with a 1A load on each winding to allow a little leeway WRT heat . I was under the impression for a 15VA core , the regulation is approx. 15% . So far two samples have been provided . First one came in 7.6V off load 6.8V on load (exactly the same as a 230V:6.3+6.3 15VA unit) , second one 7.4V 6.6V . For the tests both 6.3V secondaries were loaded with 5 ohm resistors on 15cm leads which actually exceed ratings of the transformer but the output volts are still too high , even after a few hours . Due to this , the heat is excessive in comparison to other 15VA units in stock . I have explained that the transformers are for heaters and I would prefer the on-load volts at the required current to be 6.3V +/- 0.1V and I have requested a 240V primary , the mains around here is typically 238-246V . It's like banging my head against a brick wall as they have a three week lead time including samples , I'm now six weeks in since initiating the order and I'm having to make-do with 230V:6+6 units which seem to work perfectly but have slight mechanical noise . I've never had this problem before and wondering if I am actually specifying the transformers incorrectly in the first place

Al

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Kimber Kable

Topic - Transformer regulation question - Al Noakes 15:23:40 07/15/14 (7)

RE: Transformer regulation question - wheezer 11:46:43 07/16/14 (0)

RE: Transformer regulation question - Al Noakes 07:21:21 07/16/14 (3)

RE: Transformer regulation question - GSH 08:04:40 07/16/14 (2)

RE: Transformer regulation question - Al Noakes 13:12:00 07/16/14 (1)

RE: I'll add a couple of things - Russ57 10:01:41 07/17/14 (0)

RE: Transformer regulation question - GSH 20:09:15 07/15/14 (0)

RE: Transformer regulation question - Paul Joppa 17:39:33 07/15/14 (0)

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