Gary covered it all quite nicely (no surprise there!) and I am of the same
mind as he, i.e., replace the main power supply caps (the "big can")
*FIRST* before you put much "on" time on the radio. You do *NOT* want to risk
the power transformer!
You will need a heavy-duty soldering gun or iron (200 watts or so) to
desolder the lugs that are soldered to the chassis. You will also need to
move the small audio transformer over to gain access to all of the lugs
without burning anything with the iron. *CAREFULLY* observe and *WRITE DOWN*
which color wires and how many go to each lug of the can (triangle, square,
semicircle or unmarked). Also note that some variants have a resistor
across two of the lugs, so note which two and the resistor value (it can
VARY!) and have a replacement resistor on hand in case you cannot
successfully
remove the old one (there is almost ZERO spare lead length to work with).
I've done close to ten (10) R-4, R-4A and R-4B models and after a
while you start to get pretty good at it. ;-)
Hayseed Hamfest has all you need in the way of replacement caps for
any flavor of R-4 or for a 2B. There is also a separate source for rebuild
kits for the AC-3 & AC-4 power supplies and I highly recommend that you
rebuild these supplies if you have one and it is still all-original (I forget
what the link is but you can Google it and find it easily enough).
73/Paul, K4MSG
In a message dated 2/4/2011 10:36:39 A.M. Eastern Standard Time,
[email protected] writes:
Neil -
You'll get two sides (maybe more!) on this. The FACTS are ...
Electrolytic capacitors have a finite lifetime. Various sources give
widely different _estimates_ of what this time 'is', and typically
settle around 10 years in _typical_ environmental conditions, whatever
those are. The cap has a paste that forms the dielectric, which
contains water. Over time, this water evaporates resulting in a loss of
insulating capabilities and/or capacity. Heat of course speeds up this
evaporation, and depending upon how much stuff is piled on top of the
radio, it can get pretty hot.
There are four main 'failure' conditions for an electrolytic. One is
that the capacitance decreases considerably, another is that a 'series
resistance' (presents as a resistor in series with the capacitor),
another is it becomes 'open', usually as a result of a corroded internal
lead, or, it just shorts out completely. All but the last one causes
the power supply ripple to increase, (HUM,) and if the last one does
happen, hopefully the power supply fuse will blow before the power
transformer is destroyed! This last one is why the FIRST thing I do
with a 'new' piece of vintage gear is check the fuse. I have found
everything from the correct fuse, to a piece of #8 copper wire....
So obviously all of our Drake gear is on borrowed time if it has the
original power supply caps. They may work for another ten years, or
they may short out today. The choice is yours, 'do you feel lucky?', or
are you a belt and suspenders kind of guy? If you feel lucky, just make
sure the fuse is the RIGHT one. If B & S, check with Tom at
hayseedhamfest.com. He has Twist-Lok caps that are a drop-in
replacement and offers a complete kit that replaces ALL electrolytics in
the various Drake radios.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Neil M Califano wrote:
> Should I recap my R-4A no matter what just because it is 30 years old?
>
>
>
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