[Hallicrafters] your 2 cents worth, please

[W4AWM at aol.com]

<<would you replace the disc caps or not>>

Hi again,

Discs usually do not fail from age like other caps do, but any cap can fail 
given the right conditions. I would start with the papers and electrolytics 
and then bring it up slowly again for a check out.  I would replace discs 
last, but since they are relatively cheap compared to the other caps 
involved, I would be tempted to replace them if I really wanted to do a 
complete recapping job.  Also overlooked by many are carbon resistors.  Some 
deteriorate with age and heat and can cause as many problems as caps.  They 
should be checked for value. The only good thing is that a value change in a 
resistor will generally not have the disasterous results that a shorted cap 
can cause.

When I do a rebuild, I make it a practice to be in the immediate vicinity at 
all times while the unit is powered up.  I will do this for several days 
until I am relatively sure there are no problems lurking. I keep the volume 
up where I can hear it and listen for problems as well as sniffing for smoke 
and an occasional feel of the tranny to be on the safe side.

Be aware of your line voltage.  Many older sets had a design limit for 120V 
max input and line voltage in many areas now runs as high as 127 volts.  The 
tranny will run hotter than normal and the overall voltages in the set will 
be higher.  I use a constant voltage tranny or a Variac (TM) to keep things 
within reason.  It is also possible to build a cheap voltage reducer using a 
filamant transformer.  There are several places on the web where you can find 
a diagrem to build one. Note that none of these remedies provides isolation 
when running an AC/DC set.  Only a true isolation tranny can provide this 
protection.  I buy them whenever I see them reasonably priced at hamfests.  I 
was lucky enough to find a case of them at a hamfest several years ago and 
have built them into most of my AC/DC sets.  They are installed so that they 
can be removed without a trace should I decide to sell the set to a pureist. 
For my money, they are very cheap protection, especially in the case of 
communications receivers where most of the cabinets are metal. I also install 
either polarized or 3 wire cord sets on the units I overhaul. They, too can 
be removed sans a trace, but I want to run my sets and want the protection 
for myself and any visitors who might want to tune around a bit. 

73,  

John, W4AWM


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