anyone know How to refurbish Large caps?

[gto127]

I know this might sound ike a crazy idea but large Caps in the audio grade are getting hard to find & are expensive. For instance I have a Nakamichi PA7II amp with huge 33000uf caps & I can't just replace them with anything since it would ruin the internal looks & value of the amp. People that have seen this amp know it's a work of art on the inside. So I was thinking caps have electrolyte just like batteries I suppose. Does anyone know of a way to drain & refill the electrlyte of these caps & what type of chemicals to use? Any help would be appreciated. Donald

[es44]

That sounds like an impossible task.
You could go another way.... Most new capacitors are physically smaller than the "old" ones they replace, so You could empty the old can, and put the empty shell over the new one, that way the amp will still look original.
I know this method is used a lot in restoring old tube gear, so why not in transistorized too

Best regards
Ebbe

[jacco vermeulen]

More like a scam when the amp ever gets sold.
Easier to look for identical size NOS caps and wrap the outer foil of the originals around them for looks.

The Nak sure shows that it's the 2SA1302/2SC3281 amp stage that does the labor.

[woody]

I could be wrong but.. Electrolitic caps use a verry thin aluminum
foil with the electrolitic reacting with the foil to form the oxide
layer. By the time a cap has "dried out" a lot of the electrolite
has reacted with the aluminum. Just replacing the electrolite
if it could be done wouldn't replace the aluminum that has been
used up.

[gto127]

What's the best way to remove foil without breaking it? Also will any cap the same size & value work work? I didn't think they used audio grade back then but I could be wrong. Thanks Donald

[jacco vermeulen]

You've never heard of "Elna for Audio"

In the late Nak PA7 years i foreign-ordered myself poor on "Japan Awdio" caps, from ceramic particle critters and Ruby-C BlackHoles up to straight from Nippon bamboo types, had there been Coconut caps i would have bought them as well.

The electrolytics in your PA-7 are 100V types, but 75V models will do, seriously oversizing voltage rating remains the fashion.
For some obscure reason i still fancy surgical tools, but how about a simple box cutter ?

[gto127]

So do you simply cut a slit down the middle,pull off then glue onto the new cap?. ...Yes I know of Elna but finding audio grade in this size is next to impossible. At least in the US. Do you know of a source for this? Donald

[Andersonix]

How does one tell if the old electrolytic caps are 'bad' and need replacing? Or is it just an assumption with age (not my age, the cap's) or one's particular comfort zone? Do the better brands last longer? I've seen (heard?) old no-name ps caps still going after over 30 years.

Is it true that caps placed on their side 'dry out' toward the higher side and lose performance faster? (I only just heard about this, um, phenomenon in another thread....)

[poynton]

What is this thing about "Audio Grade" or "Computer Grade" ?

Modern caps, like DNM T-Caps are probably smaller and 'better designed'.

Andy

[wakibaki]

Unfortunately with some things it's a choice between functional and historical accuracy.

Caps have changed in size as technology has moved on.

Most people take the view that it is better to have a 95% vintage airplane or car that works than a static display that's 100% accurate.

Bite the bullet and do an honest refurbishment. Any other working amplifier of this vintage will presumably have required or will require similar work. Do a neat and serviceable job and it will have an artistry of its own. If necessary fabricate an adapter.

w