| Author |
Message |
stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
|
| Posted: Sat Jan 12, 2013 6:54 pm Post subject: Never judge a book by it's cover, same for capacitors. |
|
|
Just because a electrolytic capacitor looks good don't mean squat.
I am repairing a Lexicon pre-amp/processor that is acting much like a funky power supply. I pulled the supply and did a visual inspection and nothing stood out. So I decided to pull all the electrolytics and test them out of circuit even though my ESR meter is "supposed to" be able to check them in circuit. I test them all and all well within 20% of their rating.
Oooops, forgot to check the ESR. Sure enough, there's a 1800uF 10V cap with a ESR of 3.9 ohms. I take a closer look at the cap and the board where it was mounted and see that it has been leaking from the bottom. 
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
|
|
| Back to top |
|
 |
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Sat Jan 12, 2013 6:57 pm Post subject: |
|
|
Lexicon DC-2?
SC
|
|
| Back to top |
|
|
stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
|
| Posted: Sat Jan 12, 2013 9:13 pm Post subject: |
|
|
| ecrabb wrote: | Lexicon DC-2?
SC |
Close DC-1
It was picked up for free along with a pile of 2 channel amps and a couple of Crestron devices that were headed for the dumpster (Carver M-4.0t, Parasound HCA-800II and Acurus A250.) Now that the lexicon is fixed, I have something to feed the amps with to test them. Supposedly, one of the amps is missing a channel.
Anyway, I wanted to get this thing going AND I didn't have a 1,800uf capacitor kicking around so I got creative (and brave) and decided to make something that was higher voltage and close enough in capacitance to get it going.
I used two 1000uf 35V that actually measured out to 1935uf. Close enough. Let's give it a shot. Yeee Haaaa
Works perfectly
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
|
|
| Back to top |
|
|
Tinman
Joined: 09 Mar 2006
Posts: 1326
Location: Carson City Nevada
|
| Posted: Sat Jan 12, 2013 9:16 pm Post subject: |
|
|
This is common. The low voltage caps, especially very high capacity low voltage caps tend to leak.
Being a power supply filter, anything even remotely close, say a 2200uf would be fine. Even a 1000uF would work. Just not as long, because of the aging.
_________________
This space for rent.
|
|
| Back to top |
|
|
Motobias
Joined: 08 Jul 2008
Posts: 163
Location: Osnabrueck, Germany
|
| Posted: Tue Jan 15, 2013 7:01 pm Post subject: |
|
|
picked up for free with some amps... you suck !
_________________
Most peope talk about HD without knowing the meaning and how to do it RIGHT !
FIGHTING STUPIDITY SINCE 1983
|
|
| Back to top |
|
|
stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
|
| Posted: Sat Jan 19, 2013 7:07 pm Post subject: |
|
|
So if you were eyeballing a circuit board for problems, how much time would you spend looking at this?
| Description: |
|
| Filesize: |
92.97 KB |
| Viewed: |
4797 Time(s) |
|
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
|
|
| Back to top |
|
|
stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
|
| Posted: Sat Jan 19, 2013 7:18 pm Post subject: |
|
|
or this
| Description: |
|
| Filesize: |
84 KB |
| Viewed: |
4790 Time(s) |
|
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
|
|
| Back to top |
|
|
Motobias
Joined: 08 Jul 2008
Posts: 163
Location: Osnabrueck, Germany
|
| Posted: Sat Jan 19, 2013 7:50 pm Post subject: |
|
|
any cap should get some attention...they suck !
_________________
Most peope talk about HD without knowing the meaning and how to do it RIGHT !
FIGHTING STUPIDITY SINCE 1983
|
|
| Back to top |
|
|
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Sat Jan 19, 2013 8:14 pm Post subject: |
|
|
Can't the caps go bad just by evaporation, and show no signs whatsoever of degradation? When I recapped the PSU in my Extron switcher last year, they all looked like brand new. Swapped the caps out, and bada bing, good as new.
SC
|
|
| Back to top |
|
|
stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
|
| Posted: Sat Jan 19, 2013 10:29 pm Post subject: |
|
|
And last but not least.....
This is a 1800uf 10V capacitor being seen and measured here. Looking at the display on my meter, which reading would you most be worried about?
| Description: |
|
| Filesize: |
123.3 KB |
| Viewed: |
4749 Time(s) |
|
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
|
|
| Back to top |
|
|
CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
|
| Posted: Sun Jan 20, 2013 11:26 am Post subject: |
|
|
| stefuel wrote: | | So if you were eyeballing a circuit board for problems, how much time would you spend looking at this? |
None at all cause its not attached to a circuit board.
|
|
| Back to top |
|
|
stridsvognen
Guest
|
| Posted: Sun Jan 20, 2013 2:08 pm Post subject: |
|
|
| ecrabb wrote: | Can't the caps go bad just by evaporation, and show no signs whatsoever of degradation? When I recapped the PSU in my Extron switcher last year, they all looked like brand new. Swapped the caps out, and bada bing, good as new.
SC |
They sure can.. I have a lot of bad Philips 100uf 25V 030KO axial caps who look perfect.. They can have perfect capacity and bad ESR and the other way around.
http://www.ebay.com/itm/121006773649?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
|
|
| Back to top |
|
|
Tinman
Joined: 09 Mar 2006
Posts: 1326
Location: Carson City Nevada
|
| Posted: Thu Jan 24, 2013 11:13 pm Post subject: |
|
|
| stridsvognen wrote: | | ecrabb wrote: | Can't the caps go bad just by evaporation, and show no signs whatsoever of degradation? When I recapped the PSU in my Extron switcher last year, they all looked like brand new. Swapped the caps out, and bada bing, good as new.
SC |
They sure can.. I have a lot of bad Philips 100uf 25V 030KO axial caps who look perfect.. They can have perfect capacity and bad ESR and the other way around.
http://www.ebay.com/itm/121006773649?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 |
First of, NEVER buy "vintage" caps. 
_________________
This space for rent.
|
|
| Back to top |
|
|
|
|
