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Romy the Cat wrote:

This is a technical post.

I've made some progress on my assault on the above version of EAR 834. After hard (mostly because of my idiocy)

labouring through the soldering, I've creeped to the level where I can make some static tests.

I must say the biasing of the second stage is a pure mystery for me: +270 on the rail, 330k load, -0.9V

theoretically cuts the tube out according to the curves or I'm completely out after all the solder fumes?

I do get +270-273V on the B+ rail (accross the first 150u fileter cap), I have -0.92V on

the divider (R13 -R14 junction) but tyhe plate is anywhere from 110V to 140V depending on a tube.

For the experiments I use some cheap Chinese

(one I've already sent to hell) and one TAD specimen. The tubes are CCS heated at the ideal 150mA and in fact

they want to stabilize at somewhat lower heater voltages from 10.8V to 11.8V instead of 12.6V, but perhaps

that's a Chinese crap.

Perhaps -0.9V quoted above is a mistake? Theoreticaly the

47k-10k divider gives 1.1V from 6.3V (I have a 12.6V heated so I adjusted the bias to the published 0.9V).

Anybody able to clarify/help? The 1st stage is +/- ok at 100-110V but the bias is rather -0.8V then -1V.

Thanks in advance.

PS I also do get quite some wideband noise at the output (no 100HZ though)...will investigate, perhaps

the VR's (I've put them close to the 2nd & 3rd stages).

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