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recapping a kustom (walkthrough with pics)


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so i acquired another kustom a week or so back and it's hissin something awful.i'm thinking it's got a couple of bad transistors in it somewhere but the interior of the amp is just in bad shape and with noise issues like this it never hurts to recap em (especially since the caps are nearing 40 years old).

i got a bit of {censored} in my last rebuild thread for being so vague so i'll go a little more in depth with this one and explain why i'm doin what i'm doing.





basicly what the filter caps do in an amp is help filter out any remaining ripple in the post rectified voltage and store that voltage so that when the amp needs it - it will have it.when caps get old they do several things - what we are concerned about here is their filtering properties. kustoms were a little underfiltered and noisy when new so we are gonna up the value of the caps to help filter some more noise out as well as give the amp a bit more headroom before it breaks up.

on to the info :)

here is what the old caps look like (the round things with terminals on top) :



these caps are "technically" still good (they meter out at about 41 volts when the amp is on). they are computer grade mallories and there is no telling what they cost new back in the day (they are still about 13 bucks a piece wholesale :eek:).


here's the new caps :




we are going from 4500 mfd@ 50 volts to 6500 mfd @65 volts max.this jump in the mfd rating should give us a bit more headroom and more filtering.


the cap clamps in the amps are riveted to the chassis and i want to keep the amp looking as stock as possible so drilling new holes in the chassis is out of the question. the new caps are almost twice the physical size of the old ones so we'll have to get inventive with our mounting.

so first off you should check to make sure any residual voltage is drained off the caps.

i took a pair of industrial strength wire nippers and cut the bottom of the rivets off :


after that it's just a matter of unscrewing the terminals and clamps and pulling the old cap out :


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i decided to take bend the old clamp out just a bit to let the new caps fit into the old clamps (remember i didn't want to drill out the chassis and i would have had to if i installed new clamps).

so the plan of action is to drop the new caps in, bend the clamps around them, hot glue the bottom of the cap to the chassis and clamp. and zip tie the clamp back together. this is not the most elegant looking solution from an internal point of view but the caps are mouted well enough that you can pick the whole amp by grabbing them - good enough for me :)

here they are ready to be glued,screwed and tattooed :)








now that that is done i still have to trouble shoot the rest of my noise issues and will repost subsequently when i get that worked out.

feel free to ask any questions :blah:

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Those caps are such a pretty shade of blue.

I like the use of hot glue to secure them...great idea I'd *maybe* have stumbled upon after weeks of mulling.......



computer grade mallories are a thing to behold.i lucked up and found these at an electronics closeout reseller for 98 cents a piece :)

building pedals you sometimes have to compromise and do weird things to keep from having to put screws through the enclosure and the hot glue is a trick i learned doing those. as long as you warm the chassis up first (i usually use the nose of the glue gun or a hair dryer) you can get a really strong bond between the component and chassis.

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Looks very inneresting GM. There's an old Kustom unit complete in the Seattle craigslist right now. I hate to let you have all the fun but I'm nut deep in house projects. So, "ROCK ON" brutha!


kustoms are cool amps but like anything else from that time period they have their issues. this one seems to have all the problems that these era amps get so hopefully this thread can be of some use to someone.

one of the interesting things about em is that kustom didn't use any protection on the traces on the circuit board in their early amps. the traces are copper so they have a tendency to oxidize over time and turn green like a penny.

i'm still hunting for the correct replacement transistors and when i swap em out i'll snap a few pics of the oxidation before i clean it off - it's pretty freaky looking :)

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