[Hallicrafters] S-27 Help Needed (Again)

[Richard Knoppow]

----- Original Message ----- 
From: "Joe Connor" <joeconnor53 at yahoo.com>
To: <hallicrafters at mailman.qth.net>
Sent: Thursday, May 09, 2013 9:29 AM
Subject: [Hallicrafters] S-27 Help Needed (Again)


I need your help again because the intermittent problem with 
my S-27 has come back.

The receiver plays well. After being on for about an hour, 
it sometimes goes dead. With a signal injected on the plate 
of the 1st RF (956), I get reception. With a signal injected 
on the grid of the 956, however, I get nothing. After the 
set cools off for an hour or so, reception is normal.

I've cleaned the pins on the 956, as well as the socket, and 
substituted several NOS 956s. This does not bring reception 
back. Voltages and resistances on the 956 socket are normal.

I have a couple of suspects: (1) C-4, a .002 cathode bypass 
cap on the 956; and (2) C-5, a 330 pf screen bypass on the 
956.

Do you think leakage in either of those two caps could cause 
my symptoms? Is it possible that one of these caps develops 
leakage only when the set has been on for a while? Can I use 
a regular film cap for the cathode bypass?

As always, thank you for your guidance.

Joe Connor
______________________________________________________________

     I forgot to ad that using freeze mist or a small heat 
gun may help to find out what is causing this.


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