Need some capacitors (where to buy 6800uf 63wv)

[ik632]

I have a Harmon Kardon receiver that I used to really like until it started to hum (I wish it could carry a tune, hahaha). So, after calling HK to see what the repair cost would be (they estimated $150 because they knew which two caps it was that were defective) I decided to do it myself.

Apparently a run of amps from around 1999-2003 had some bad main caps for the amp section and they have been replacing them, and making a fair amount of money on out of warranty amps during the process. The tech even directed me to the place on the board where they are and, low and behold, there are two big caps with bulging, practically round tops. No wonder the amp buzzes/hums like it does.

So, now I need to buy some replacement caps and I'm not entirely sure where to get them from. I would like to make sure that they will sound good once installed, but I don't need the super high audiophile quality ones that will cost more than the amp is worth. From what I understand they should be $10-15 each for good quality caps. They are 6800uf (I don't have a micro letter on my keyboard) and 63wv(volts). Anyone have any good sources to get these from? I think this is all I need.

Now, my other issue is how to determine which is positive and negative on the old ones so I am sure to re-install the new caps correctly?

[richidoo]

There is shrink label around the cap cans which has a stripe pointing to positive, or is it negative? It is clearly marked, but note the orientation before you remove the parts.  Take a pic of the cap polarities before you disassemble in case of brain fart.

These are power supply caps so audiophile grade film caps are not necessary, and aren't even made that big. Xicon is decent and cheap, also Panasonic, nichicon, etc.  Measure the original caps' width, so the replacements will fit on the board. 6800 is very popular size so there will be skinny and fat ones to suit any need. Get wire leads for easiest soldering, not snap ins which have larger stamped leads.

http://www.mouser.com/Search/Refine.aspx?N=2203862+4294626251+4294438773

Rich

[ik632]

Cool, so I can pretty much buy whatever I want then.

[Carlman]

Nichicon's listed on that site are supposed to be pretty good, reliable and to spec.
I've used them for PS caps on an amp with good results... I can't vouch for the other brands listed.
Glad you found the hum!  You'll have it singing the words in no time!

[mgalusha]

The Panasonic TSHA series are very good and Digikey has them in stock. They are available in two sizes, 30mm x 50mm and 35mm x 40mm.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P7489-ND

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P7490-ND

They are snap in as are most that size but I'd bet $20 the originals are as well. Be sure they are discharged before working on it. Even though the original caps are failing they will still hold a charge. Check with a voltmeter be sure everything is discharged before poking any body parts in.

[ik632]

One is fully discharged and one reads 16v. Is that low enough where I can just short the leads or should I use a resistor?

Also, still trying to figure out which is +/-. The caps that are there don't have proper markings. There is a negative symbol on the top, but it's not in line with the leads on the bottom. I'll try to get some pictures this weekend. I could always bring it to Rich's and get some professional advice this weekend

[pmkap]

ik632,

I've found that the quality of the main ps caps in an amplifier to have significant impact. I use the Nichicon Muse KG series, but Mouser is presently out of stock in the larger 63v values, and the KG in the 6800uf is 35mm in diameter by 50mm high, and might not fit in the space provided. Mouser does carry the new Muse KW in that value with a more manageble 25mm x 50mm footprint -
http://mouser.com/Search/Refine.aspx?Keyword=UKW1J682MRD

Nichicon asserts that these are significantly better than the KG type I caps, but also doesn't mention how close these newer caps are to the KG type IIs (of which Mouser is out of stock, and are the cap series I use in what I consider an excellent amp, the Aspen Soraya).

These are radials, not snap ins, but should fit in either hole configuration.

FWIW,
Paul

[richidoo]

Nick, sorry for the delay. I have been checking New Posts and not checking New Replies, so sometimes they slip by me.

Soraya     If it's good enough for that perfectionist highend showboat, it's good enough for vintage Technics! I can't wait to come to NY to hear it Paul. Maybe this summer.

Nick, you can discharge the caps with a resistor across the cap leads, making a RC filter with time constant controlled by the resistor value. If you use a 1/4W resistor, make it high enough resistance to not discharge too fast and burn up the cap. You're the engineer, so I'll let you do the math, but you can find a RC calculator online. stereofool posted some such websites here in the past.  Connect the resistor with some clipleads.
http://cr4.globalspec.com/thread/3090/How-to-Calculate-Capacitor-Discharge-Resistor-Values

With the amp running or recently turned off (since it apparently holds a charge after shutdown) you can use the voltmeter to check the polarity of the caps when charged. Be careful not to touch anything in there!!

[ik632]

Got them out, they are 30.2mm diameter x 41mm tall and 10mm pin spacing. Looks pretty standard size wise so I should be ok to go. Brand is Chemi-Con from Korea.

I looked at that link and that cap is 25x50 but it has 12.5mm spacing, so it's a bit big for the holes in the board. Since the caps are so big, I don't want to have them supported by the solder joints either.

[ik632]

I think I found the same model Chemi-Con, is there anything bad with replacing them with the same model Chemi-Con, aside of course, of the fact that these are what went bad in the first place?

[ik632]

Looks like all of the Nichicon FW's are all 25x50x12.5 and the KW (higher sound quality) are the same size. It looks like the snap-in have the correct pin spacing. Now that I think about it more, would there be any issue with using the larger spacing? I could push them down until they just about hit the board and put some hot glue beneath the cap.

[ik632]

Here are the bad guys:

Is that a bulge in your cap or are you just happy to see me



Brand and model:

[richidoo]

Get the Nichicons if you can fit them in, versus a no name brand. I would stick with the original terminal spacing and skip the glue because you may have to do this again sometime. Get the cap down hard  on the PCB for stability. Of course, get the same voltage and temp ratings (or better).

[ik632]

I can't find the Nichicons in that form factor so I may need to go with the Chemi-Con's. Those seam to be pretty popular but not as audiophile quality as the Nichicon KW's. The Nichicon's do come in a snap in in that general size, but diameter is 35mm so they are going to be too big to fit in. There are two boards on either side and it was already very tight with the 30mm caps. I might just order the ones I know will fit and the ones I know will sound better and try them both.

[richidoo]

Sure, the Chemi cons were good enough for Technics, right?