[Hallicrafters] SX-71 UPDATE

[Oliver J. Dragon]

Gary,

Thanks for the detailed description of your SX-71 recap. I am learning a 
lot from your
notes and adding them to the file of experiences that you and others have 
passed along
to the rest of us. These details will be of great help and guidance in the 
future as I tackle
the recap of various boatanchors. I'm sure there are many others here that 
are storing
(if only mentally) the info in personal archives.
Please keep up the great work. Thanks again!

Ollie

At 08:47 AM 02/26/2006, GBrown wrote:
>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
>
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