Brett -
Those are what used to be called "Twist-Lok" caps, or at least that was
Mallory's name for them. There are four tabs around the rim of the
mounting end that go through either slots or a central hole in the
chassis. When slots are used, the tabs were just "twisted" to "Lok" the
cap can to the chassis, or for the mounting method that Drake used the
tabs were just bent out over the edges. One tab is soldered to ensure a
reliable ground connection.
Soo... Removal is somewhat difficult for a couple of reasons.
1. The tab soldered to the chassis requires a LARGE soldering iron or
soldering gun to transfer enough heat to melt the solder..
2. The wire used by Drake is _extremely_ heat sensitive, so that even
having a large iron nearby is enough to melt or at least deform the wire
insulation.
The procedure I use is to FIRST make a careful drawing, or better yet a
digital photo of the area to record which terminal each wire goes to.
Once you are satisfied you can replace each wire to the correct
terminal, which are the + terminals of each capacitor, as close as possible.
Once the wires are out of the way, look at the brown phenolic insulator
on the bottom of the cap. You'll see a Triangle, Square and Half Round
figure etched in the phenolic by each of the + terminals. The
replacement cap will have the same figures to identify the _different_
sections of the capacitor. If you get your replacement from Tom at
<www.hayseedhamfest.com>, the etched figures will be in the same order
as the original.
Removing the tab soldered to the chassis is the hardest part of the
process. Push all the wiring as far as possible from the soldered tab,
then apply your LARGE iron to the tab. When the solder melts, twist the
capacitor can to get the soldered tab away from the solder area on the
chassis and free it. Then bend up the tabs and remove the can.
Insert the new can in the hole, carefully orienting the etched figures
exactly like the original. Using your drawing and/or photo, strip and
connect each wire to the appropriate terminal and solder _carefully_,
and with a big enough iron to heat the terminal, solder quickly and get
off so as not to melt the insulation on the wire.
As usual, much more difficult to describe than do, but there are
pitfalls along the way, primarily the heat sensitivity of the wire
insulation. If the insulation DOES pull back in spite of your best
efforts, be sure that the bare wire does not touch anything. The wire
is solid, so it holds it's position pretty well. If you have some
insulation from another piece of hookup wire, slip it over the bare wire
if you can.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Brett Forehand wrote:
Ok, I've been told there's no such thing as a stupid question... so
here goes! How do you remove the canister caps in the R4C? Do they
just unplug, do they come out with a twist and pull, or do you have to
unsolder them from the bottom of the chassis?
Thanks,
Brett
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