[Hallicrafters] SX-71 UPDATE

[GBrown]

Just a few notes to anyone who mite be starting a recap job on a SX-71.
First thing I done was cut the line cord of the radio. This removes the
temptation to plug it in. I went over the schematic diagram, made notes of
suspected areas of attack. Removed the one line bypass cap rated at 600
volts and replace with one rated at 1.6kv. I also added another one to other
side of line. Next I jumped to the electrolytic and unsoldered all
connections while drawing a little diagram. You never know, if your like me,
your going to forget which wire went where and spend time tracking down the
connection on the schematic. I did notice that when I removed the
electrolytic can cap, two twist lugs were soldered to the chassis. LOOK
AGAIN, it looks like there soldered but I will bet you the solder has
separated or all most separated from the chassis. I tested the cap, all
three sections were a little leaky so I restuffed it with NOS caps and
reinstalled. I did resolder the two tabs to the chassis and also ran a
ground from one of the tabs to a known good ground. Next area of
concentration is the audio section. As we all know, Hallicrafters radios are
very susceptible to failure in the audio section. With no questions asked,
changed out ALL the caps in this area. The cathode resistor had gone up
about 300 ohms. This is a MUST change also in allot of radios with any age.
CHANGE THAT CATHODE RESISTOR. When you do change it, put one in that's a
little bigger wattage, if possible. I had tested all the tubes. Seeing they
were all logoed Hallicrafters. Most were weak and one had an open filament.
If you have a capacitor checker, make sure to check all the micas and those
double duty disc ceramics. Well, that's about it for yesterday, will be
headed back to the shop today to tackle some more areas that need attention.
Before I forget, I don't think I saw a line fuse in this radio.
NOTE: Install line fuse when installing new three conductor power cord. And,
one other little tip. When you remove a component, just clip a jumper wire
to where the part was. This saves some head scratching after you come back
from dinner.
All have a good weekend.
Regards,
Gary...WZ1M