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Vintage dave (talk | contribs) (ADAPTING THE TYPE W PLUGIN TO USE 6DJ8 or 12AT7 INSTEAD OF 8416) |
Vintage dave (talk | contribs) (formatting) |
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A) Add 100 ohm 5W in series with R290. I put it on a | A) Add 100 ohm 5W in series with R290. I put it on a | ||
three-point terminal strip bolted to the top of R290. | |||
B) Add isolated current source across V124-V214-V114. | B) Add isolated current source across V124-V214-V114. | ||
Start with either a 6V-24V step-up transformer (details below), | |||
rectifier and reservoir, or a shielded switching supply powered | |||
by +350V. The current regulator is just an LM317 with a | |||
resistor between OUT and ADJUST, and take output from ADJUST. | |||
Two 1/4W resistors in parallel, one 18 ohm, the other 12 ohm, | |||
gives 180mA, raising the total to 360mA. Or two 15's and a 100. | |||
The supply must handle 100V backfeed if a tube burns out. | |||
Just put a diode in series. That's why I regulate current | |||
instead of voltage. | |||
2. 12AT7 | 2. 12AT7 | ||
A) Add 1200 ohm 2W in parallel with V124-V214-V114. This | A) Add 1200 ohm 2W in parallel with V124-V214-V114. This | ||
bypasses 30mA around the tubes, reducing the heater current | |||
from 180mA to 150mA. | |||
B) Tek used XV214 pin 9 as a tie point. It must float when | B) Tek used XV214 pin 9 as a tie point. It must float when | ||
12AT7 is used, because it's heater center-tap. | |||
C) V114B and V214B grids must be biased 3V positive for | C) V114B and V214B grids must be biased 3V positive for | ||
successful operation of the Q154-12AT7 cascode. | |||
Details below. | |||
3. OTHER TYPES - NOT TESTED | 3. OTHER TYPES - NOT TESTED |
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