176 Limiter DC Pulse Value?

[CJ]

trying to estimate any residuals from 6AL5 rect in side chain,

want to calculate DC effect on core,

12BH7 is push-pull,  about 33 ma balanced DC if 11 V thru 330 ohm cathode bias is correct,

but what about side chain current thru windings?  power transformers take this into consideration, full wave vs bridge circuit magnetizing waveform varies so VA must be compensated ,

thinking there might be some DC mag current thru 6AL5  but how much?

thanks for any help,

upload folder still  full so>

https://img1.wsimg.com/blobby/go/0e07cc59-2f5a-481f-967d-12c7363b86fa/downloads/1d111mqap_711908.gif

 

[PRR]

The rectifier is full-wave. Same as a 5U4 power bottle: the DC is cancelled in the core. (Long-term... short musical transients will be asymmetric.)

The 6AL5 is like a 1mA device. Actually rated 9mA steady 50+mA peak. 9mA into 0.1uFd is 90,000 volts per second, so the cap charges in like a milliSecond. After that the steady current is maybe 10V in 1Meg or 10uA.

I think if you have balanced 33mA already, you could round-up 10% and over-cover all rectifier loading.

 

[CJ]

Thanks PRR!

looking at core size vs inductance for different interleave patterns for a 176 output transformer,

using a 4500 turns coil on a square stack of EI 87  (7/8" tongue)  29gaM6 (grain orient silicon .014")

inductance at 20 Hz for different stacking :

Butt Stack - no paper gap: 187 Henries (perm = 2200)
Divide Core into 4 Chunks (alternate chunks 1 x 1) 313 Henries  (perm 3700)
Lap 3  (3  lams this way, 3 lams that way) 748 Henries (perm 10,000)
Lap 1    1128 Henries  (perm 13, 300)


looks like a Lap 3 will give plenty of inductance and still withstand a little unbalanced direct current,

we only need 238 Henries  to make a 30 K wind at 20 Hz,  so we could either use a more DC bullet proof 4 x 4 core or reduce turns on a Lap 3 and save DCR at the expense of some inductance , the balancing act begins,  4000 turns is a nice round number, we could even use a bigger wire size but wait, that means more capacitance, so stick with 4000 turns of the same gauge and maybe use more insulation to get good freq response at the hi end,

what is P to P resistance of the dual  triode 12BH7a ? not listed in the tube book, made to run  as a vert deflection amp in Zenith 25" TV,  5300 ohms triode, should be less as push pull so 30 K  from the transformer s/b plenty.  what about thumps?  too much inductance might make good response at 5 Hz, so be careful there. (just talking to myself here, ignore if possible) 

gut feel says  try 4000 turns with maybe a 5 chunk core lacing.  only 2.8 K Gauss , tons of headroom for low distortion at bottom end,

 

[CJ]

a gapped core makes for stable core,

did a quick graph for 87 EI

gapped vs laced core at 20 Hz,