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Replacing Large Electrolytics
On 8/28/18 4:15 AM, Cursitor Doom wrote:
If you're a professional repair tech, I can see why you would only use new parts. But I'm just a ham; a hobbyist. And we hams have been successfully reforming electros for many decades without any adverse outcomes. Loads of info on the net it you care to look for it, but I'm guessing since you're a pro you'll turn your nose up at the very thought! Hams are notoriously cheap. And the internet is a cesspool of useless information. I've been a licensed Ham for 50 years now. You wouldn't believe some of the butchery I've encountered on Ham radio gear. I have a phrase for it. Joe "Claw Hammer" Ham has been here. Apparently having a ham license gives you the ability to think you know more than any commercial engineer. That being said, I've used old NOS capacitors for myself. But I don't waste my time reforming them. They either work right the first time they have power applied or they don't. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
Replacing Large Electrolytics
if there is room, just leave the old cap in place and wire a new one in parallel.
m |
Replacing Large Electrolytics
On 2018/08/28 6:43 AM, wrote:
if there is room, just leave the old cap in place and wire a new one in parallel. m That is only good advice if you first cut the old cap out of circuit. Many capacitors fail by increasing their leakage or outright shorting out. If the capacitor is suspect replace it. John :-#(# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
Replacing Large Electrolytics
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Replacing Large Electrolytics
On Tuesday, August 28, 2018 at 9:43:42 AM UTC-4, wrote:
if there is room, just leave the old cap in place and wire a new one in parallel. m And when the old one fails short? Peter Wieck Melrose Park, PA |
Replacing Large Electrolytics
On Tue, 28 Aug 2018 11:07:13 -0400, Ralph Mowery wrote:
If I am doing things for myself, I may do anything to get equipment going. If I were doing things for others, it would be with good parts. Like the time at work an outside repair person came in to repair a 3 phase motor drive unit. He found 2 out of 3 diodes bad. I told him to replace the 3 rd one. It may have been under stress or not. He said they were $ 200 each. Told him it costs us $ 1000 or more per hour while that equipment was down, so $ 200 is good insurance it will not quit in a short time. That 3 rd diode would probably last , but why take a chance at those rates. And that is the very core of this issue: economics. As a hobbyist, I'm only fixing up my own stuff and if it goes wrong again in a couple of years owing to the NOS parts I used having failed - I don't believe they will for a moment but simply for the sake of argument - then it's no big deal at all for me. It's a totally different story for professional repairers who would be foolish indeed to install anything other than good quality new parts from a reputable supplier. Sure it costs more, but for a pro, it's well worth it for all sorts of reasons. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition. |
Removing Large Electrolytics
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote:
Sounds about par for the course. Go back further to paper caps and it'd be a surprise to find any still working properly. And yes, micamold were paper caps. I've got a box full of the oil & paper caps that come in cubiod cans and they all tested fine (I have an awful lot of vintage spares here). Not so sure about the tubular paper caps which I assume you're talking about, though. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition. |
Replacing Large Electrolytics
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Replacing Large Electrolytics
On Tuesday, August 28, 2018 at 10:54:07 AM UTC-7, Gunther Heiko Hagen wrote:
On Mon, 27 Aug 2018 14:02:45 -0700, wrote: On Monday, August 27, 2018 at 12:50:00 PM UTC-7, Terry Schwartz wrote: ...Spend the $25 and get new parts... Here in Silicon Valley, it would be a lot less. 4700uF/35V and 5600uF/42V are both available at retail for under US$1 each. Can you kindly provide a link to the supplier you refer to who's able to offer such truly extraordinary prices? Anchor Electronics, 2040 Walsh Avenue, Santa Clara, California 95050 USA http://www.anchor-electronics.com/ https://anchor-electronics.com/price-list.pdf Electrolytic capacitors are on page 13. I am a retail, over-the-counter customer. I do not know about their mail order policies, except the last page of the price list says "We Ship To USA & Canada Addresses Only." |
Removing Large Electrolytics
On 08/28/2018 01:47 PM, Cursitor Doom wrote:
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote: Sounds about par for the course. Go back further to paper caps and it'd be a surprise to find any still working properly. And yes, micamold were paper caps. I've got a box full of the oil & paper caps that come in cubiod cans and they all tested fine (I have an awful lot of vintage spares here). Not so sure about the tubular paper caps which I assume you're talking about, though. Moisture + acid paper + foil = mess. That'll take a lot longer if the cap has metal on five sides. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com |
Removing Large Electrolytics
On Saturday, 1 September 2018 20:48:34 UTC+1, Phil Hobbs wrote:
On 08/28/2018 01:47 PM, Cursitor Doom wrote: On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote: Sounds about par for the course. Go back further to paper caps and it'd be a surprise to find any still working properly. And yes, micamold were paper caps. I've got a box full of the oil & paper caps that come in cubiod cans and they all tested fine (I have an awful lot of vintage spares here). Not so sure about the tubular paper caps which I assume you're talking about, though. Moisture + acid paper + foil = mess. That'll take a lot longer if the cap has metal on five sides. Cheers Phil Hobbs My prewar metal can paper caps are all wax sealed, and every last one tested dead as a very dead thing. The non-metal seal is where it can go wrong. Not sure why they didn't use bitumen. NT |
Replacing Large Electrolytics
On Friday, August 24, 2018 at 10:35:43 PM UTC-7, Fox's Mercantile wrote:
On 8/24/18 6:42 PM, Cursitor Doom wrote: I had 3 faulty electrolytics; all 30V/5500uF. In my spares bin I found 6 NOS (new old stock) electros ... These spares, though unused, are probably 40 years old. Will they need re- forming gradually over 24hrs before installing? Reforming is a fool's game. They either work to being with or they're bad. That's not ny experience; yes, I might toss the 40--year-olds, but only because new ones are cheap and probably better performing. Even one-year-old capacitors can benefit from reforming, though, and for some uses (timing capacitors) it's beneficial. It doesn't take 24 hours, though: with a current-limited supply, just give 'em 150% of the rated voltage and warm 'em with a hair dryer for a few minutes, while watching the leakage current. You can see it drop from milliamps to microamps. |
Replacing Large Electrolytics
On 9/2/18 3:15 AM, whit3rd wrote:
It doesn't take 24 hours, though: with a current-limited supply, just give 'em 150% of the rated voltage and warm 'em with a hair dryer for a few minutes, while watching the leakage current. You can see it drop from milliamps to microamps. That's not how manufacturing does it. Their installed and at the end of assembly line, full power is applied. They either work or they don't. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
Replacing Large Electrolytics
On Sun, 2 Sep 2018 06:03:04 -0500, Fox's Mercantile
wrote: On 9/2/18 3:15 AM, whit3rd wrote: It doesn't take 24 hours, though: with a current-limited supply, just give 'em 150% of the rated voltage and warm 'em with a hair dryer for a few minutes, while watching the leakage current. You can see it drop from milliamps to microamps. That's not how manufacturing does it. Their installed and at the end of assembly line, full power is applied. They either work or they don't. I remember when part of my job was fixing power supplies. Some that failed the automatic part of the test last thing on one day would work the day after. I never found out why that happened but I assumed it was an electrolytic so I changed the lot. Steve -- http://www.npsnn.com |
Replacing Large Electrolytics
On Sun, 02 Sep 2018 06:03:04 -0500, Fox's Mercantile wrote:
That's not how manufacturing does it. Their installed and at the end of assembly line, full power is applied. They either work or they don't. That's all very well for *brand new* capacitors! -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition. |
Removing Large Electrolytics
On 2018-08-28 10:47, Cursitor Doom wrote:
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote: I've got a box full of the oil & paper caps that come in cubiod cans and they all tested fine (I have an awful lot of vintage spares here). Enjoy your PCBs. |
Removing Large Electrolytics
On Sunday, 2 September 2018 20:38:38 UTC+1, +++ATH0 wrote:
On 2018-08-28 10:47, Cursitor Doom wrote: I've got a box full of the oil & paper caps that come in cubiod cans and they all tested fine (I have an awful lot of vintage spares here). Enjoy your PCBs. and not the good type NT |
Replacing Large Electrolytics
On Sunday, September 2, 2018 at 4:45:44 AM UTC-7, Stephen Wolstenholme wrote:
On Sun, 2 Sep 2018 06:03:04 -0500, Fox's Mercantile wrote: [about electrolytic capacitors] Their installed and at the end of assembly line, full power is applied. They either work or they don't. I remember when part of my job was fixing power supplies. Some that failed the automatic part of the test last thing on one day would work the day after. I never found out why that happened but I assumed it was an electrolytic so I changed the lot. Electrolytics have to be formed (kept under bias for a period) before they develop the dielectric (oxide) layer, AND that layer is continuously renewed when they're under bias. On the shelf, however, it degrades. Some switchmode power supplies (the old Apple II types) rely on timing capacitors for startup sequencing, and the power filter electrolytics are NOT the prime suspects when such a power supply doesn't work. You can often fix those power supplies by leaving 'em turned on overnight. The most plausible reason for this is that the timing capacitors (not the big filter caps) have to be re-formed. This syndrome can't be improved with new filter capacitors (I've tried). Once they work, they're reliable again. |
Replacing Large Electrolytics
Once upon a time on usenet John Robertson wrote:
On 2018/08/25 11:23 AM, Cursitor Doom wrote: On Sat, 25 Aug 2018 10:39:13 -0700, John-Del wrote: Heat and charge cycles do affect a capacitor's life, but they're not the only factors. Humans who smoke, drink, and do drugs have a shorter life than those who don't, but we all will die eventually. Hmmm. Not really a valid analogy! I've had plenty of electros in stock go off value, become leaky, and go up in ESR just from sitting in a nice quiet bin. I don't install any cap without running through my Z meter, and I will toss an entire lot of caps if one is bad. I managed to find 8 electros in my bin that could used in parallel to get the equivalent of the failed ones I've removed. I've checked them all for ESR, leakage and Capacitance and the readings I've got have come out indistinguishable from new caps of the same value & voltage rating. I've picked the best 6 (with the lowest ESR) and am re-forming them over the course of this weekend. I'll report back in due course on the success (or failure) of this method. I certainly wouldn't want to hit them with their rated voltage straight away after so long in limbo as that *would* be inviting disaster. The final test is leakage, set the cap up with an ammeter in series and put it on a power supply running around 75% of the rated maximum voltage. Leakage should be very low after the cap has stabilized. Here is a nice write-up: https://www.nmr.mgh.harvard.edu/~reese/electrolytics/ Heathkit made a great cap checker that we use to check older off the shelf NOS caps. Has the Magic-Eye tube and everything - except ESR. Thanks for that link. -- Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders) |
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