[Hallicrafters] help on model s-51

[Richard Knoppow]

----- Original Message ----- 
From: <ralphcuda at cox.net>
To: <hallicrafters at mailman.qth.net>
Sent: Wednesday, January 12, 2011 5:38 PM
Subject: [Hallicrafters] help on model s-51


>I have an S-51 that's been sitting for 20 yrs. and when I 
>power it up I hear a hum and I don't have any volume 
>control. I don't see all the tubes light up. Is there a 
>place where I can have the tubes checked out? I live in 
>Florida. Any help would be appreciated. Thanks.
> ralphcuda at cox.net

   The filaments are mostly series string but V-5, the audio 
pre-amp, and V-6, the power amp, are supplied through a 
series resistor and there are a couple of dropping resistors 
in parallel with V-5 and the resistor. If this resistor goes 
out the entire string will run at low voltage and V-6 won't 
light at all. Check this resistor, R-44 marked as 15 ohms.

     There might be enough ripple on the power supply so 
that you get some hum directly through the output 
transformer. Make sure the some tubes are really not 
lighting. Since this set has series string heaters if any go 
out all will fail with the exception of V-6 where the 
dropping resistors across it might allow enough voltage for 
the tubes to glow a little (maybe). I suspect the trouble is 
something else.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com