anyone know How to refurbish Large caps? - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd January 2009, 03:38 AM   #1
gto127 is offline gto127  United States
diyAudio Member
 
Join Date: May 2007
Default anyone know How to refurbish Large caps?

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
  Reply With Quote
Old 23rd January 2009, 07:02 AM   #2
es44 is offline es44  Denmark
diyAudio Member
 
es44's Avatar
 
Join Date: Apr 2005
Location: Fredericia, DK
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
  Reply With Quote
Old 23rd January 2009, 10:25 AM   #3
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to 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.
Attached Images
File Type: jpg nak pa7_inside1.jpg (48.4 KB, 233 views)
__________________
The buck stops Here
  Reply With Quote
Old 23rd January 2009, 11:00 AM   #4
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
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.
  Reply With Quote
Old 23rd January 2009, 03:30 PM   #5
gto127 is offline gto127  United States
diyAudio Member
 
Join Date: May 2007
Default Easier to look for identical size NOS caps and wrap the outer foil of the originals a

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
  Reply With Quote
Old 23rd January 2009, 04:19 PM   #6
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to 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 ?
__________________
The buck stops Here
  Reply With Quote
Old 23rd January 2009, 05:57 PM   #7
gto127 is offline gto127  United States
diyAudio Member
 
Join Date: May 2007
Default For some obscure reason i still fancy surgical tools, but how about a simple box cutt

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
  Reply With Quote
Old 23rd January 2009, 06:06 PM   #8
diyAudio Member
 
Andersonix's Avatar
 
Join Date: Jan 2004
Location: Silicon Valley, California
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....)
  Reply With Quote
Old 23rd January 2009, 06:36 PM   #9
poynton is offline poynton  United Kingdom
diyAudio Member
 
poynton's Avatar
 
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
What is this thing about "Audio Grade" or "Computer Grade" ?

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

Andy
__________________
If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote
Old 23rd January 2009, 06:55 PM   #10
Banned
 
Join Date: Jan 2008
Blog Entries: 2
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
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Large caps Stuart Easson Swap Meet 26 25th March 2009 04:57 AM
Paralleling small value caps with large value PS caps xyrium Power Supplies 16 14th October 2005 05:06 PM
Where to buy large caps in Europe? Sony Pass Labs 7 8th May 2005 12:16 PM
Is it OK to add a large bank of caps outside the amp? mattjk Solid State 4 15th November 2004 04:18 PM
Large caps in PSU without choke? G Tubes / Valves 14 5th March 2004 03:10 PM


New To Site? Need Help?

All times are GMT. The time now is 01:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2