[Heathkit] SB-200, Good News or Bad??

[Kenneth G. Gordon]

On 14 Aug 2007 at 14:30, Scott KBØNLY wrote:

> Ok, after spending another hour at the bench.. 
> 
> If i disconnect the lead from pin 2 of the left tube socket, looking
> at if from the rear, which is the one that feeds C16, and solder a 50
> ohm resistor to it and the nearest ground lug here is the latest...
> 
> With the capacitor value changes as shown on NE7X's website i can get
> a nearly perfect 1.2-1.5:1 swr on each band with careful tweaking of
> the input coils.

Good. That is now finished. On to the next possible problem.

> 
> So this would assure me that the input coils, the new cap values, and
> the bandswitch are all AOK and working fine.  So now the question is
> what the heck is wrong?  Is it bad tubes or?

Bad tubes. Weak socket connections. (I had to replace one socket in 
MY SB-200).

What brand(s) of tubes are presently installed?

Do you have any spares?

Looking at the tubes with the top cover open, do you notice any 
difference in the COLOR of the filaments?

Are the tubes different sizes?

In a parallel tube GG linear amp, there is really no need for "matched" 
tubes, unless you are using TV sweep tubes. With the usual GG triode, 
like the 572B or 811, you don't need to worry about matching.

But, some of the foreign so-called "572B"s, aren't really 572Bs.

Ken Gordon W7EKB