Re: SE fixed bias VibroChamp works; toob math question


"Phil S." <psymonds_no_spam@xxxxxxxxxxx> wrote in message
news:SaudnYRaLqKRHPHbnZ2dnUVZ_h-vnZ2d@xxxxxxxxxxxxxx
Ok, I fixed the bias supply and the amp seem to be working on the bench.
I haven't plugged in the guitar yet for a taste test. Not redplating
<grin>. Most voltage readings appear reasonable, but screen is still above
plate by about 2V.

I'm feel iffy on the toob math for a change. Here is the data from the
one random GE 6AQ5 I plugged in. There are two readings, bias pot moved
from one extreme to the other:

G1: -13.25; -14.10
A: 266; 269
Across Rk, Ia : 41.27mA; 38.33mA

This tells us Pout:
10.98W; 10.31W
Is that right? Couldn't be right.

Duncan Munro's TDSL says for Class A, SE:
G1: -12.5
A: 250
Ia: 45
I calc this to be 11.25W, but the TDSL says Pout = 4.5W

I'm not getting this.

Also, bias voltage range seems to be wrong. Should I change the bias pot
to give a wider range and more R, like from 50z to 100z?

Help, please!

Thanks.
Phil


I said 50z and 100z pots above. I meant 50K and 100K. There is a 68K R in
series with a 50K pot.


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