VintageKustom.com: Repairing Kustom Amps » I'm finally having my K200 tuned up :-D

Re: I'm finally having my K200 tuned up :-D [message #5267 is a reply to message #4993]

Mon, 03 January 2005 16:21

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

That is the part number for a 2500 MFD cap, the K200s use a 4500MFD 50volt cap.These are electrolytic type caps, meaning wet like a car battery.When they make these caps, inbetween the aluminum foil they use for the plates they put a electrolite compound, then they run a small voltage and current thru the cap for anywhere from minutes to many many hours. The current passing thru the electrolite produces a aluminum oxide film on one side of the foil. this is the dielectric or insulation from one layer of foil to the other. the thickness needed of this insulation depends on how much voltage the cap will be rated at, and in turn how long the forming process takes.So they are growing the insulation inside the cap. Now heres the problem, as they age, heat and non-use makes the electrolite dry up, once that starts the cap can not keep up its dielectric and the stuff will start to crystalize. What repair techs can do some times if they are not to dry, is reform the caps, just like when they first make them.This repair will work for a while depending on how much voltage the powersupply hits the cap with, compared to how many volts the cap is rated at, and once again like some people have heard how offten the amp gets used. Use is better for cap life.But be ware once what ever amount of electrolite goes crystline inside the cap, that hard stuff can never be reverse, and even worst once crystline it becomes a conductor of electicity just the oposite of what it needs. It may not conduct enough current to blow the amps fuse( but at some point it will) but the amp will start to get a 120 cycle A/C hum out of the speakers and it will go into distortion and sound ugly at a lower and lower volume level.You can replace the caps with a larger MFD value for more clean head room and tighter bass control, but from what I have found, any thing more than 15000 MFD on each side of the powersupply is a waste and a big expence if you go for new caps in the same size 3 inch size cans. Back when this amps where made they wanted to use the best caps, and they did, these are called computer grade caps. now a days caps have come a long way, you can get 3 times the MDF value in a cap all most 2/3s smaller then what came in the amp. This smaller type will need smaller mounting clamps, but what I do is just silicone glue them in, or tie strap them to the original filters if still good and then add some glue. Do not be tempted to use shoe goo glue or a tube type contack cement, you will regret it later. The silicone is plenty strong!

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