W/Repairs: Difference between revisions

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45 bytes removed ,  10 May 2022
formatting
(ADAPTING THE TYPE W PLUGIN TO USE 6DJ8 or 12AT7 INSTEAD OF 8416)
 
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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.
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),
Start with either a 6V-24V step-up transformer (details below),
  rectifier and reservoir, or a shielded switching supply powered
rectifier and reservoir, or a shielded switching supply powered
  by +350V.  The current regulator is just an LM317 with a
by +350V.  The current regulator is just an LM317 with a
  resistor between OUT and ADJUST, and take output from ADJUST.
resistor between OUT and ADJUST, and take output from ADJUST.
  Two 1/4W resistors in parallel, one 18 ohm, the other 12 ohm,
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.
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.
The supply must handle 100V backfeed if a tube burns out.
  Just put a diode in series.  That's why I regulate current
Just put a diode in series.  That's why I regulate current
  instead of voltage.
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
bypasses 30mA around the tubes, reducing the heater current
  from 180mA to 150mA.
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.
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.
successful operation of the Q154-12AT7 cascode.
  Details below.
Details below.


3. OTHER TYPES - NOT TESTED
3. OTHER TYPES - NOT TESTED
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