Help with radiating 60 cycle hum introduced at the input Xfo

[CJ]

wow, this reverse wind bizzness really does affect inductance!

Sec current draw at 20 Hz and 2 V-ac for the fwd-rev coil pair is 31 micros

Sec current draw at 20 Hz and 2 V-ac for the fwd-fwd wind coil pair is 42 micros

so reverse winding increases the inductance of this coil/core assy dramatically,

let's crunch the numbers,

2V-ac/.000031 = XL = 64,516 Ohms for rev wind

2V-ac/.000042 = XL = 47,619 Ohms for fwd wind

Rev Wind Ind. = 64,516/6.28 = 10,273  divide by 20Hz to get Henries = 513.7

Fwd Wind Ind. = 47,619/6.28 = 7583 divide by 20Hz to get Henries = 379.2

so we get an increase percentage wise of 513.7/379.2= 1.3547 = 35.47 percent increase, 

we noticed an increase in the Reddi OPT's that we reverse wind but nothing like this,

let's do Quality Factor at 20 Hz,
Sec DCR = 247 Ohms, XL for rev wind is 64,516, so 64,516/247= 265.5 not too shabby, QF for non rev wind is 47,619/247= 193 still very good,

i bet there is a trade off in freq response on the rev wind , that is up next,

 

[CJ]

this reverse wound xfmr starts rising at 25 K Hz and peaks from 2V-ac output to 4.85 V-ac at 110KHz
the screens/core lead decreases this peak down to 2.5 V-ac when hooked to the finish of the sec
no effect is seen when hooked to other leads, this may be because this xfmr does not have the foil wrapper which would tend to balance leakage C. we will wrap this one tomorrow and see if it is the wrapper or the rev wind that causes the difference between screen effects,

this fwd wound xfmr starts rising at 25 K Hz and peaks from 2 V-ac output to 5.2 V-ac at 110 K Hz,
hooking the screens/core lead to either of the sec leads decreases this peak from 5.2 to 4.43 volts,
hooking the screens/core lead to any of the pri leads has no effect on the peak voltage, this may be due to the fact that we are driving the xfmr with a signal generator instead of a mic,

 

[midwayfair]

CJ, this is awesome, and way above and beyond. Thank you! 

Good material for the DI-Windings thread, too.

 

[CJ]

yes transformers are fun because you can build them, ever try building a transistor? what a drag,

we found some old UTC cans that will make a nice home for these guys,

so we wrap the lams with cloth tape to hold them, and then wrap the whole enchilada in kraft paper to keep it centered and take up space so we do not have to use as much wax, and it keeps the leads insulated just in case,

shield and core gnd go to a #4 standoff, xfmr can be mounted by way of the standoff's on the other side,
gonna take a template to get the holes right, or you can low tech and use tie wraps, but it would be nice to have that case grounded to the chassis so the hum goes down,

 

[CJ]

heat gun on high to melt this stuff, pour it in and let it cool, don't fill the can the whole way, do it in two steps,  because that wax will contract and leave sink holes that cave in from the top, ever seen an old school jar of preserves that your aunt mildred use to make, the wax is concave on top, now everybody eats fruit rollups how toxic are those?  ;D

we will final test these and run some ringing tests today and then ship it out for a blind rev vs non reverse wind test by the perpitrator of this project, ain't gonna tel him which can is which, blind test from 1000 miles away,

 

[CJ]

what else can we do with these transformers,

ever play thru one of those hi-dollar Alembic F2b preamps that people shell out 1600 for,
nice, but a street boy can't stack that much coin,

what if you had a DIY version but wanted to drive cables into 600 with that 12AX7a?

just flip these things around and run them 4:1 for a little gain reduction that matches up with a line input better, don't want to distort a A to D, you've heard what that sounds like, right?

tried it out with the preamp of this DIY Princeton and it sounds pretty good, gonna wind another coil and use line level lams as we get a little too much crunch at full volume with the hi-octane stuff,  run it off the .1 cap, don't want DC on that Ni core, plus, the tube starts conducting 4 ma into that reduced DCR as no 100K plate R,

looks like another Neve input next to the cans how did that get in there?
well we added an XLR for open mic ego trippers,  ;D

i'm out...

 

[midwayfair]

heh, the UTC cans are a nice touch

 

[Gene Pink]

...now everybody eats fruit rollups how toxic are those?  ;D

Wassa matter with fruit roll-ups?

Name another food product that you can fax to someone, with no loss in quality.

Gene

 

[PRR]

> Name another food product that you can fax to someone, with no loss in quality.

Un-frosted Pop-Tarts improve with faxing.

(What is a fax?)

 

[CJ]

did a sq wave test on these 1:4  jobs and there is no ringing, those screens must have something to do with that, also, the xfmr without the outside copper wrapper shows no difference in ringing or freq response, so it must be for noise,

my dentist use to hand these out for Christmas, backpacker's worst nightmare,

 

[CJ]

print for this 1:4 mic input,>