diytube.com

I think we have a winner...

Brown pairs with brown/white, and green pairs with green/white.

You got it !

I didn't have the docs on the transformer handy when I
put it together, and figured it out real quick when the
tubes didn't light up.

You win a pair (or two) of gold plated pcb octal sockets !



... tom

I measured the primary and see:

128 ohms end to end
57 ohms B+ to screen tap
71 ohms screen tap to plate end

... tom

OK, now how about the primary's inductance - if one doesn't have an LCR bridge handy


I posted this over at Edcor's forum, and I'll share it here, as well:

(Someone was inquiring as to the primary inductance of the XSE15-8-5K, and received a somewhat "evasive" reply)

You can calculate a rough primary inductance "guesstimate" with this simple formula, which is based on the old standard calculation for inductive reactance.

Z = 2*pi*F*L (F in Hz, use your lowest frequency; L in Henries).

Turning that around,

L = Z / (2*pi*F) in order to keep the math simple. I'll call pi as being 3.14 - we don't need to go out to the 99th significant digit for this application

in the case of the XSE15-8-5K, this would be:

L = 5000 / (6.28 * 70) or in round numbers, 5000 / 440 = 11.36H for a minimum value.(70 Hz)

For the GXSE-15-8 this would work out to 5000 / 251 = 19.9 H minimum. (40 Hz)

If you have SE-CAD from John Broskie, you can plug these numbers into the Transformer listing.

IIRC, the DCR of the XSE15 primary is around 128 ohms, and the secondary is around 0.5 ohms.

Actual measured inductance values may be somewhat different, and they will change as the DC current in the primary winding is increased.

I have some XSE15-8-5Ks,, GXSE15-8-5Ks and GSXE10-8-5Ks on order, and I can do some actual test measurements on them after they arrive.

/ed B



Old school method of calculating Pi with only a cheap or vintage "four banger" calculator: Just remember the number sequence 11 33 55, and then divide 355 by 113, and it comes out to Pi out to the 7th or 8th decimal point.

355/113 = 3.1415929 on a cheapo 8-digit calculator ;D

/ed B

EWBrown wrote:Old school method of calculating Pi with only a cheap or vintage "four banger" calculator: Just remember the number sequence 11 33 55, and then divide 355 by 113, and it comes out to Pi out to the 7th or 8th decimal point.

355/113 = 3.1415929 on a cheapo 8-digit calculator ;D

/ed B

Thanks for the tip, Ed. I've often thought to myself, "How I wish I could enumerate pi easily, since all those bullshit mnemonics prevent recalling any of pi's sequence more simply."

The other "lazy pi" is simply 22/7 or 3 1/7.

Works out close enough for tube-ology, anyway.

2*pi*60hz = 377, which comes in handy for figuring XC or CL at AC power line frequency.


Anyhoo it's all good for approximation (as in good enough for government work).

/ed B

You guys do know that all tube-ology calcs must be done with a slide rule don't you?

Calculators should only be used for sand-based circuits......

You guys do know that all tube-ology calcs must be done with a slide rule don't you?

Some concession can be made for the younger 'uns who get by with a Curta.

A vintage"four-banger" calculator with nixie tube display is "fair game" to use.

Extra points if you have one of the Wang Calculators.

OK, keep your mind outa da gutter, Wang was a computer company


http://www.oldcalculatormuseum.com/wang362e.html

I work at it's last remaining vestiges, until May 29th.

/ed B