Hi again,
Regarding a grid drop resistor
I am using two resistors;
A: a 500 ohm 10 W from HV- to GND in HVPS.
B: a 500 ohm 10 W from HV- to GND in RF deck.
C: a 3A Si-diode is also connected between HV-
and GND in parallel with resistor B;
anode is grounded, cathode is connected to HV-.
I am using a 0.2 ohm shunt resistor for IP meter,
and a 2 ohm for IG meter between these 500 ohm
resistor/diode and the bias diode/cathode of the
tube in the RF deck; these 500 ohm resistors
practically provide no or little error on the meters.
de Han JE1BMJ
----- Original Message -----
From: "Marius Hauki" <rezycle.bin@gmail.com>
To: <amps@contesting.com>
Sent: Friday, September 10, 2010 7:03 AM
Subject: [Amps] GS35B questions
Hi, I am working on a new GS35B HF amp design.
Some questions:
-I would like to buy some sockets instead of machining them myself.
Could you gentlemen direct me to a person selling sockets that
normally have them in stock or at least can deliver within a month or
so?
-What is the proper "burn in" procedure for the GS35B? I was planning
on running the filament of the tube for some time (how long time?)
with proper airflow. Do I need to apply HV as well? I don't have a HV
tester at the moment. I bought the tubes from UR4RLL. They look new /
unused.
-I am planning to use the triode control board from WD7S. Any things
that I should be specially aware of when using that board with the
GS35B (apart from the mod for higher bias voltage)?
-I am planning 3650V on the anode. This is significantly higher than
the "official" data sheets state, however I notice that the official
data sheets rate the tube for military service with less cooling. Does
3650V look like an OK voltage?
-I am looking for a SAFE way of running the HV cable from an external
HV PSU cabinet to the RF cabinet. I know this has been discussed
numerous times before, but again: what is the best cable I can use and
what connector should I use? Did we reach a conclusion and some
reccomendation on that question? I would like to avoid any possibility
at all for the B+ (hv plus)connector connecting before the B- (hv
minus) because that may place the RF deck at the HV+ potential if the
grounding between the two boxes are broken. (I do not plan on hot
plugging, of course). The minus lead should be isolated from the
chassis since I plan on using a high wattage drop resistor from
chassis ground to B- to be able to measure grid current.
-Should I place the grid drop resistor in the PSU cabinet or in the PA
deck? I was thinking that placing it in the PA deck would be safer
because in case only B+ is connected before B-, the grid drop resistor
would connect B- to chassis ground and not keep the PA deck at B+
potential (No I am not going to hot plug the B+ connector, but perhaps
some other operator will attempt just that. You never know what can
happen in the mid of a contest battle)
-I have read that running DC instead of AC on the filament is OK.
However I have read somewhere else that it is not OK. I have an AC
trafo, but if the primary voltage varies, the filament voltage could
be too high or too low and this may hurt the tube. Instead I would run
a regulated DC supply, since the filament current is not that high.
Any comments on that? Alternatively, any clever way of regulating the
trafo by a small series drop resistor or something?
73
LB3HC
Marius
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