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Capacitor leak

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Posted on May 8, 2017 at 20:16:42
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 Found a small puddle of oil(?) on the bottom cover of my Scott 340a tube receiver when I removed it. Maybe dime to quarter in size and right under one of the electrolytic caps. It hasn't leaked any more. It's been two days and the unit still sound excellent.

Is it possible that I can leave it the way it is...as long as it continues to sound good? I would have to send it out to be fixed as I have no tools or skills to DIY.

So far there is no hum or distortion.

Thanks for any opinions/advice.

 

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A very bad sign if truly from one of the electrolytics ..., posted on May 8, 2017 at 20:37:25
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 ...seal has been breached and will either dry out and become ineffective over relatively short time period or catastrophic failure imminent (messy). Should be replaced before further use. IMO of course.

 

RE: Capacitor leak, posted on May 8, 2017 at 20:42:32
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 DIY skills or not, a cap. physically leaking fluid must be replaced. Electrolytic caps. go bad, over time, and require periodic replacement. Their life, while decades long, is most definitely finite.

Put on rubber or vinyl gloves before cleaning the crud up. It's highly alkaline in nature and has to be treated with respect. Dilute acid will neutralize the alkali and make the clean up easier. Vinegar will work, but the aroma could be problematic. Bottled lemon juice, from the grocery store, gets my nod. Follow up the chemical neutralization with dampened paper towels or cloths. Leave zero residue.


Eli D.

 

Electrolyte, posted on May 8, 2017 at 23:53:49
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 I've never seen mention of strong alkali in capacitor's electrolye. In fact strong alkali are highly corrosive to aluminum, same as strong acids.

In early capacitors, electrolyte was solution of boric acid in glycerol. Nowadays they use ammonium tetraborate solution in ethylene glycol for regular capacitors, and in dimethyl formamide for low temperature-rated ones. These electrolytes are not very corrosive, but they can cause shorts if they leak onto other components.

Ethylene glycol is toxic (it is same stuff as antifreeze).

 

If it's one of those old paper type..., posted on May 9, 2017 at 06:07:08
FenderLover
 Like Mallory or Astron --- with age, leak nearly all the time. I always replace these.

photo IMG_0436_zpsegfk0uvg.jpg

photo Pro_Amp_PS_new2_zps32crapih.png

 

RE: If it's one of those old paper type..., posted on May 9, 2017 at 07:05:35
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 It is a Mallory type FP. Is there a chance this unit could still play for a few years "as is"?

 

You have photo of cap?, posted on May 9, 2017 at 07:13:01
FenderLover
 I would replace it. CE makes some nice replacement cap cans. I like to use the highest voltage rated ones (in correct mfd range) ---- as long as the new can fits the chassis. You'll have longer life.

You do risk other components, if the main PSU caps fail. To me, the $35-50 for a new can is worth it.

 

Thanks below..., posted on May 9, 2017 at 07:15:18
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 As I mentioned to FenderLover, It is a Mallory. It has not leaked any more and the unit sounds good.

This unit came from a friend and he can repair it if needed. Problem is, this unit is in "like new" cosmetic condition and shipping will be done as a last resort. I just wonder if I'm at the last resort or the next to last resort.

 

RE: You have photo of cap?, posted on May 9, 2017 at 07:23:20
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 Thanks for the fast response and suggestion. It came in as I was typing a thank you above. The problem is...having to ship this for repair and risking damage to its pristine condition.

As long as it sounds good and no hum and no more leakage, I wonder if there is a slim chance I could get by as is.

edit...I'll try and post a picture a little later.

 

Kinda up to you., posted on May 9, 2017 at 07:32:45
FenderLover
 I've always replaced old caps, esp those that leak, have "pimples," or feel "light" because of evaporated electrolyte fluid.

How hard will you or your friend be playing the unit? And make sure the fuses are the correct amps.

Good luck!

 

RE: Kinda up to you., posted on May 9, 2017 at 07:49:37
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 Good questions.

I have a couple of systems and this unit/system will only be played occasionally and never at high volumes. On of my criteria for choosing pieces is they have to sound good a low volumes and this one sounds real nice.

Fuses are correct. There will be no wrapping in tin foil. :-)

I'd replace the cap in a heartbeat if shipping was not an issue. Circuits can be repaired but bent faceplates, etc can not. The drive to his place would be very difficult at this time and it would have to be twice, once to drop it off and again to pick it up when done.

If this was even a 9 out of 10 cosmetically I'd ship it but this is as close to a 10 as I can imagine. That's why I would hold out and hope for the best.

 

RE: Thanks below..., posted on May 9, 2017 at 08:08:29
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 An "FP" type cap should never leak. The typical FP failure mode is "drying out" with attendant low cap value/high ESR. A leaking FP cap can fail catastrophically turning your 9+ cosmetics into a "for parts or repair" unit. From my POV, your decision is binary; do what it takes to get it repaired or make it a " display only" unit.

 

RE: Kinda up to you., posted on May 9, 2017 at 08:38:27
Bill Way
Audiophile

Posts: 1884
Location: Toms River NJ
Joined: May 28, 2012
Contributor
  Since: December 14, 2012
 Do it. You're in southern California - should be very easy to find a tech to do it, and shouldn't be costly. If one cap leaks, it's very likely all the 'lytics need replacing. It just doesn't make any sense to run it with bad caps. At best, you're not hearing what it can really do; at worst, you'll turn it on one day for some quiet listening, hear a loud pop, then silence. I wouldn't pursue anything with the seller, unless (s)he said "Everything has been replaced inside." It is a 55-year-old piece of gear that, as you said, looks and sounds good.

BTW, you might also start accumulating spare tubes. There are 20 of 'em in there, and tubes *do* go bad, often without warning.

Good luck.

WW
"Put on your high heeled sneakers. Baby, we''re goin'' out tonight.

 

RE: Electrolyte, posted on May 9, 2017 at 08:53:57
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 IIRC, NaOH was used in, at least, some 'lytics. These days, electrolyte composition is a trade secret. Protective gloves during clean up can't hurt and may be essential.


Eli D.

 

RE: This a DIY forum, posted on May 9, 2017 at 09:45:44
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 It is time to learn some skills and what better than fixing your own amp. You just need some tools, which are a pair of needle nose pliers, the electronic variety which are smaller than the bigger all purpose type, and a soldering iron. The type of iron you get is important. For soldering point to point wiring you need an iron with a bigger tip and higher temperature heater.
Replacing an axial capacitor is one of the easiest DIY jobs you can do. 2 ways to do it. First is to mind the + and - alignment of the cap. Then just snip the 2 wires close to the body of the cap. With the excess wire put a "u" shaped bend in the end of the wire. thread the wire of the new cap thru the bend and pinch the bend and then solder. Repeat for the other side. There are tutorials online which can shown you in more detail the details. try it you will like it.

 

It's not an axial cap; it's a chassis mount FP "twist-lock"..., posted on May 9, 2017 at 10:25:24
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 ...typically a royal PITA to replace, especially if the OEM decided to solder the twisty parts to the chassis. Not the best place to start a repair learning experience.

 

RE: Kinda up to you., posted on May 9, 2017 at 10:49:12
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 Nothing to pursue with the seller, he's a good friend and we trade things from time to time. He'll fix this if I want to keep it or take it back.

Driving is difficult for me at this time so I will either wait until I can or have Fedex pack it themselves and deal with whatever happens.

Re spare tubes...I've been in the tube rodeo for the last 20 yrs with many new and vintage tube units and have many a spare tube for backup.

Thanks for the tips.

 

RE: Electrolyte, posted on May 9, 2017 at 12:05:46
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 Can you provide reference to alkaline electrolyte?

Major components of electrolyte, such as ethylene glycol or ammonium tetraborate are not trade secret. Trade secrets are minor additives (anti-corrosion, thickening agents, surfactants, etc.

 

RE: Kinda up to you., posted on May 9, 2017 at 16:16:22
llwhtt
Audiophile

Posts: 192
Location: SOCAL
Joined: October 28, 2008
 I had some CE twist locks leak on my MC30's, ran down the outside and ruined the chrome. :(

Craig

 

RE: It's not an axial cap; it's a chassis mount FP "twist-lock"..., posted on May 9, 2017 at 17:50:42
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 Getting the old FP cap. and mounting hardware out is work, but well worth the effort. Clamp mount a modern, lower ESR/ESL, part in the hole. A terminal strip, for some additional parts, can share a clamp hold down screw.

In the open air, an 85o C. rated part is OK. Under the deck, 105o C. rated parts get my nod, as they rate to have decent service lives.


Eli D.

 

RE: Kinda up to you., posted on May 9, 2017 at 17:50:44
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 MC30's = nice amps. I've had a 240 and a couple generations of the 275. if I were to get another Mac, it would be a 225 or 30's like yours.

Did you replace the leaky caps immediately or did you play it for awhile before doing so?

 

RE: Electrolyte, posted on May 9, 2017 at 18:36:03
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 The memory is old. Remember, caustic = alkaline.

A Google search came up with some links.

https://books.google.com/books?id=ABijBQAAQBAJ&pg=PA314&lpg=PA314&dq=caustic+electrolyte+electrolytic+capacitor&source=bl&ots=8E9LYSC4O1&sig=f0nHHMfzqGJe5vTBVauWkcDgM4w&hl=en&sa=X&ved=0ahUKEwi98PSSlOTTAhVi0oMKHYdGCNwQ6AEIOzAF#v=onepage&q=caustic%20electrolyte%20electrolytic%20capacitor&f=false

http://www.google.ch/patents/EP0229254A2?hl=de&cl=en




Eli D.

 

RE: Kinda up to you., posted on May 10, 2017 at 09:32:31
llwhtt
Audiophile

Posts: 192
Location: SOCAL
Joined: October 28, 2008
 They had been sitting on the shelf for a while, took them out to listen to them and noticed the streaks on the chrome. Pulled them apart, checked the ESR and the caps were dead. I then just installed some F & Ts I had on hand inside the chassis and called it a day. If I remember correctly CE had some problems when they first reissued the "FP"s so maybe this was one of their problems. I've used several since and no problems yet.

Craig

 

RE: Capacitor leak, posted on May 12, 2017 at 10:24:49
Jim McShane
Dealer

Posts: 5910
Location: Chicago
Joined: January 13, 2003
 You are taking a chance by not replacing a suspect cap. Remember that these caps have a design life - and if it was an original cap it is close to 50 years old. That's WELL beyond the design life. So it's not a question of IF it will fail, but WHEN. And no one knows when that will be.

If the cap vents it can distribute corrosive material around the inside of your unit - bad scene. And it CAN take out other components as well.

If you can identify the cap for me I'll be happy to help you find a suitable replacement. I just can't see the logic behind NOT replacing it especially if the amp is a nice one!!

 

RE: Capacitor leak, posted on May 13, 2017 at 11:45:01
onemug
Audiophile

Posts: 1276
Location: So. California
Joined: April 19, 2003
 Thanks Jim. If I keep this, when it comes to replacement I'll get in touch with you.

 

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