[Hallicrafters] SX-28A issues

[Richard Knoppow]

----- Original Message ----- 
From: "Mike Everette" <radiocompass at yahoo.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: <hallicrafters at mailman.qth.net>; <magnuson at mac.com>
Sent: Tuesday, April 15, 2014 10:43 AM
Subject: Re: [Hallicrafters] SX-28A issues


I think that all the Halli receivers with high power push 
pull audio, like the SX-11, SX-16, SX-17, SX-23, SX-25, 
SX-28, SX-32, S-27, S-36, SX-42 used the same B plus 
arrangement to feed the output tubes -- straight from the 
rectifier output, not going through the choke.

73

Mike
WA4DLF


      I got curious and checked several of these, sure 
enough you are right. They didn't on the S-27 and S-36 but 
those have a two choke filter and the output stage is 
connected at the first choke. In theory a push-pull amp will 
be immune to supply ripple.  I think you are also probably 
right about the source of hum in the OP's receiver. Either 
he has another bad cap or has miswired it somehow. The fact 
that it was working and then faded and became hummy sounds 
like a cap blowing up. In backward maybe?


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