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Old 11-16-2011, 10:59 PM
DaveWM DaveWM is offline
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Join Date: Feb 2009
Location: Orlando FL
Posts: 5,607
you can also save by using radial leads vs axial leads, a lot cheaper. I generally get nichicon's 105c rated. Check voltages, often you can get a 350v for the same as a 200v so if you need a 200v just get 350's that way you have them when a circuit requires a 300 or 350v. the also come in a variety of sizes, I like the tall skinny radials since they fit inside the old cans (I prefer to restuff the cans vs putting them in under the chassis). I have a method that I use when not too concerned about cosmetics. I have what I call a bone saw which has a receiprocating blade about 2" long. I 1st cover the chassis with paper around the can, then use the saw to cut if off just above the shoulder (about 1/4 inch from the bottom). the paper is there to catch the alum chips from the saw action. cutting at the shoulder leaves the phenolic base (which has the terminals of the can embedded in it) intact. then drill from the bottom side right along the term strips. with a center hold drilled for the common negatives. A little planning here can help to make sure the leads from the caps are in a position to allow all the caps to fit inside (up to 4) the can. Care needs to be applied to make sure the leads are next to terminals and not shorting to the chassis, there is not a lot of room for error, but its not hard. Triple check the polarity and the correct cap the correct term on the can.

by doing the above you can leave the lead dress alone as well as any parts soldered to the lugs (like resistors). I find that alone worth the effort as you don't have to spend time removing the old can and all the attached wires and parts. a typical can cap can be restuffed in about 5-10 min tops after you get the hang of how to use the saw and how to align the caps. The tall skinny ones make it much easier since they fit so easy inside the can.

for the common neg I just pig tail some solid copper wire, slide it over the common leads in the center, solder, then solder the wire to one of the already solder cap twist lock lugs. I leave the insulation in place just so its not as critical to make sure the wire does not brush up against term on the cap. again rechecking work catches this stuff (I have a very bright shop light handy for that).

after all that is done I will do a slow start with a variac, monitoring the B+ voltage and current. slowly ramping it up will make sure there were no reversed caps or shorts to worry about.

if all good then I will use a large threaded hook screw into the old cap guts, pull them out, clean the inside bottom edge of the can with some solvent, scratch it up with some 150 grit sand paper, smear some 5 min epoxy around the inside edge, positiion the can over over the base (with values pointing out so they can be read) and let gravity pull the epoxy downward and flow around the base. the 5 min is good since it's pretty thick stuff.

I will also cut some alum tape (used by hvac folks) into strips about 1/2 wide and use that to join around the shoulder, just in case some of the epoxy manages to seep out the seam.

again this is not cosmetically the best but it is fast, and IMHO the least disruptive to the overall chassis (since the bottom terminals are left completely alone, but for the new cap leads solder to them.

I take the same approach on recapping hand wired chassis, leaving the existing leads alone where they attach to tube sockets, just pig tailing the new parts in. The main reason is to properly remove the old solder and unwrap the orig leads can be some what stressful to the terms, esp on old wafer style sockets. the pig tailing done well does not look bad and certainly is a lot less stressful.

now if I was doing a museum quality restoration then I would no doubt take a different approach, but for daily drivers, esp if they do not belong to me, I go the do no harm approach even if it is not as pretty.
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