Due to shortage of some materials, my custom transformers were delayed a bit. I haven’t got chance to arrange the pickup yet, so I ask Ken to give a quick test of the unloaded voltage. I know the best scenario is to test the transformer on the real world environment with actual fully loaded rail. But you know me, that would be happening sometime later. So just a quick voltage test could be interesting –  for now.
Be noted that this test was done in Malaysia with mains voltage rated at 240 VAC (actual tested at 246 VAC as shown below). So all the secondary voltage also pulled up around 10% higher than the actual specification which was designed for 220 VAC input.
Sorry the pictures are not that good as I have told Ken before, he needs to upgrade his camera!
The first is the first filament, should be rated at 6.3 VAC at 220 VAC, but with 246 VAC input, the value hit the 7.16 VAC.
Second filament which should be rated at the same, also measured the same 7.16 VAC. What a consistent or precision winding.
Next is the 4V winding for my RGN rectifier filament, read at 4.41 VAC.
The 5V windings for RGN rectifier filament. Read at 5.68 VAC.
The high voltage winding. Hmm… looks yummy at 356.8 VAC.
Exactly the same value for the rest half of the winding. Quite precise work!
The lower voltage of the high voltage winding. Read at 267.8 VAC.
I guess you can expect the same VAC for the rest half of the winding. Yes you are correct, the value read exactly the same with the first half of the winding, 267.8 VAC.
Will wait for the transformer to come, test at 220 VAC input, and also loaded with my preamp.
triodethom
November 11, 2014 06:50Look very good . Small resistors may be need to lower voltage on the heater taps or a common mode choke inline . Other voltages look spot on to me. Looking forward to your test results. Regards
Auw Jimmy
November 11, 2014 10:34Hi Triodethom,
I hope no resistor is required as they act very bad and unstable to drop high current.
With 10% increment from actual design of 220VAC input to 246VAC actual mains, then the 7.16VAC @ 246VAC also expected to drop around 10% @ 220 VAC, so be around 6.4-6.5VAC without load. Hope the actual will follow my math!
Thanks.
triodethom
November 14, 2014 04:15A current sensing resistor is stable . 6 to 6.6 is fine on heaters . I like 6.0 to 6.25 . A common mode choke should drop the voltage range enough . Look forward to see how this very nice transformer turns out. J& K chokes look good also .