Fw: SB 102 Plate current

[Glen Zook]

Several possibilities:

Your 6146 tubes could be weak.

Your driver tube could be weak.

This all "assumes" that the rig has been properly
aligned.

Finally, the meter "shunt" for the panel meter to read
correctly is the six 10 ohm resistors in parallel from
the cathodes of the 6146 tubes to ground.  These very
often change value.  If they go high in value, the
meter will read high.  If they go low the meter will
read low.  The total resistance of this combination is
supposed to be 1.6 ohms.  Use a good digital ohmmeter
to measure this.  Make sure you take into
consideration the resistance of the leads (short them
together and note the value - i.e. 0.6 ohms).  Then
look for a resistance of 1.6 ohms plus the resistance
of the leads (i.e. 1.6 + 0.6 = 2.2).

Replace the resistors with new 10 ohm 5 percent 1 watt
resistors (the original are 1/2 watt) and then check
the value again.  You may have to add a slightly
larger value resistor in parallel with the six to get
the correct value.  I had to add a 22 ohm in parallel
with the six 10 ohm resistors in my SB-110A to get
this value.

These resistors changing value seem to becoming a
major problem in the SB series transmitters and
transceivers.

You can get these resistors for 14 cents apiece from
Mouser in small quantities and 5 cents apiece in
quantites of 100.  I suggest getting at least two sets
(12 resistors) and keeping a spare on hand.  Even with
the 1 watt resistors instead of the original 1/2 watt,
it is possible to "stress" these resistors and cause
problems.

The use of carbon film resistors in this circuit
causes no problems.  That is the type of resistor that
is readily available.

You can get 1/2 watt 10 ohm 5 percent resistors from
Radio Shack.  However, they come five to a package and
you will spend almost as much money getting the six
resistors that you need than from Mouser getting the 1
watt size with the spares.  Of course, you have to pay
shipping from Mouser.  However, that penalty is worth
having the better resistors.

If you have a local source of 1 watt resistors, of
course, use it.

Glen, K9STH


--- JERRY JUDY <jer-xenia at WORLDNET.ATT.NET> wrote:

On my SB 102 the manual says not to exeed 220 mils at
resonance. I cant get more than 190 mils max on mine.

the meeter says I have good high voltage. Any ideas?


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