Dear QRO lovers,
I am a happy owner of a Drake L4B . I have replaced the tubes to
new ones, RFP 3-500ZG. I have change all
components except the transformer in the power supply. The amp works great.
The maximum HV is abt 2500 volt from the standard Drake power supply.
I have order a new transformer according to my own specifications,
primary 2 x 400 volt 2-phase,(not ordinary 220 volt 1-phase),
and secondary 700, 900, 1100, 1200, 1300 volt, 1200VA 100% duty. I will get
from 1900 to 3600 volt DC.
The data sheet for 3-500Z says maximum dc plate voltage 4000 volt, ( I will
use max 3500v)
Now to my question:
1."Typical operation" says:"Zener diode positive bias at plate
potentials of 3 Kv or more"
How do I make +10 - +15 volt positive bias?
2. Can the Drake L4B circuits handle an output power of 1,5 Kw?
3. A positive voltage of 120 volt from a resistor divider is applied to
the cathode during standbye. Do I need to increase this voltage when I
increase the plate voltage?
73 Tomas / SM6VVT
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