[Hallicrafters] Re: Hallicrafters Digest, Vol 25, Issue 34 SX28 XFMR

[PROZACH7 at aol.com]

Joe:
 Re: smoke from SX28 ouput xfmr: The smoke usually means that there is a 
heavy current through the primary, which means the B+ end of the winding is not 
shorted. Pull the output tubes. Is there still smoke? If not then you might have 
an oscillating output or a short in one of the tubes or a very leaky input 
cap to the tubes that's causing the tubes to draw heavy DC current. Check the 
control grid voltage of the output tubes with them pulled and the set ON. It 
should be zero. Replace the 2000 pf cap with one having about 600 volts capacity.
 If it still smokes with the tubes pulled, then there's a semi-short 
(whatever that is!) near the plate ends of the primary. With the rcvr OFF measure the 
resistance between the primary and ground. It should be higher than say 
100,000 ohms.
 If you have to replace the xfmr, check also Fair Radio. You will probably 
have trouble finding the SX28 impedance match. A standard tube push-pull input, 
speaker output xfmr would work if you bypass the xfmr in the speaker cabinet 
and tie the output directly to the speaker terminals.
 Hope this is useful. I have 2 SX28's and fortunately have had no trouble 
with them! Lucky me!
73
Frank, W6LPU