SB-102 low drive problem

[Robert Nickels]

My SB-102 has low output on every band except 75 meters.  40 is about 
half, and 20 and above will output produce a few watts.  The tubes in 
this radio all test very good and it receives fine.  The main problem 
was is was VERY dirty, but cleaned up well.

I've aligned the receiver per the instructions using the crystal 
calibrator as a source.   Every coil peaked, no broken slugs and uisng a 
good signal generator I can hear a 1uv signal on all bands 80-10.  I've 
checked signal levels all the way up to the 2nd Transmit Mixer V6, the 
6CB6 just before the driver.   The driver grid coils are in the mixer 
plate circuit and  the RF level at the grid of the driver drops just 
like the output, even though the level of both of the mixer inputs are 
the same on all bands.  It's pretty obvious that only the 80 meter coil 
is being tuned right, yet they are peaked.  . In all the SB-100 series 
the 80 meter coil is in the circuit all the time, and a the 3F wafer on 
the bandswitch switches the coils for the other bands in parallel as you 
change bands.   I suspected dirty contacts - and they were - and I've 
cleaned them with DeOxit twice.  Checked and replaced a couple of 
resistors but no improvement.

Here's what's really got me stumped:   The same coils and capacitors are 
used on Receive as well as Transmit so how can there be anything wrong 
with them?   That's why the alignment is done using a received signal, 
once they're peaked they are supposed to be good to go on both Rx and 
Tx.     My coils are peaked, as proven by the receiver sensitivity.  Yet 
the drive level out of this stage falls like a rock as you move up the 
bands! 

I would really appreciate any ideas where to look as I know this same 
scheme was used in thousand of HW and SB radios.  I'd normally suspect 
weak finals but like the rest of the tubes, they test high on the good 
scale, and even weak finals should put out more than this.

Thanks!
73 Bob W9RAN

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