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 Post subject: Check your new electrolytics before installing
PostPosted: Jul Tue 25, 2017 8:44 pm 
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I just want to offer the suggestion to all to check those new electrolytics before you install them. In the last 6 months, I've put into 2 radios new electrolytics that were bad. Turn on the radios for the 1st time after rebuilding--terrible hum, as if you never took out the old 'lytics--tack in another new 'lytic loosely, all becomes well, and that bad new 'lytic is clipped out, & thrown in the can...which is a shame...So from now on I'm checking my new caps before installing them.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Tue 25, 2017 8:54 pm 
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Thanks... but gee ....
That's really a VERY VERY rare occurrence.
So strange... I've NEVER found a new bad cap in over 100 radios I've restored.
So.. it is quite unusual. ... certainly as far as I'm concerned.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 4:26 am 
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Location: The Old Dominion VA 23518
HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them. In the last 6 months, I've put into 2 radios new electrolytics that were bad. Turn on the radios for the 1st time after rebuilding--terrible hum, as if you never took out the old 'lytics--tack in another new 'lytic loosely, all becomes well, and that bad new 'lytic is clipped out, & thrown in the can...which is a shame...So from now on I'm checking my new caps before installing them.


Brand? Source of the caps? It's scattershot without some context. :?:

Me? 3 bad "MIEC" electrolytics, and several bad axial film caps, various, non-brand name types, with no provenance.

I tend to buy all Panasonics - they never give me trouble. Cheap, reliable, and free shipping - so easy peasy on the wallet too. I just wish they continued with the FC series electrolytics, my favorites.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 4:45 am 
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Some years ago, several major manufacturers produced entire runs of defective electrolytics.
This was due to a missing element in the chemistry of the electrolyte.

Hopefully all of those are in landfills, but you never know.

It's always possible for problems to exist on a smaller scale and get by Quality Control.
Of course, that assumes the manufacturer has such a department in the first place.

- Leigh

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 5:46 am 
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HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them.

+1 to this advice from HERSHEY; I could not agree more. Not so much with brand-new, freshly-purchased electrolytics from a reputable supplier, where failures are extremely rare. But rather for those that you may have purchased a few years ago and have been on your shelf for several years. And unless they have date codes, who knows how long they were on the shelf of your supplier before you purchased them?

Hence the reason that I always test and reform electrolytic caps before installing them. In my case I use a Sprague TO-4 TelOhmike, but there are many other options for testing them. Any electrolytic cap more than a few months old will need at least some level of reforming. Usually, with a brand-new cap of good quality, this reforming occurs upon initial power-up and all is well. But not always. My personal experience has proved to me that any electrolytic cap whose voltage is brought up gradually, while monitoring and limiting current (thus eliminating excessive heat buildup within the cap during the reforming process), is much more likely to reform properly than one whose full rated voltage is applied immediately.

This precaution may seem silly to some, but defective new electrolytic caps do indeed exist. More often it is not that they are totally defective, but rather that they may give erratic symptoms or take an unusually long time to properly reform, while bringing their voltage up slowly and monitoring/limiting current with a vintage R-C bridge-type metered cap tester such as a Sprague Tel-Ohmike, which in some cases (even if they do eventually reform) might lead one to consider whether he really wants to install them into a piece of high-quality radio/audio gear which he is restoring. And even more especially, when investing the additional labor to "restuff" them into original cap shells/cans.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 6:42 am 
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Poston Drake wrote:
HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them.

+1 to this advice from HERSHEY

+2, and not just Electrolytic's. Last year I built a home-brew receiver, and when it just wouldn't work right, began testing components. One of those little yellow .05/630 that I had just bought was the culprit. I now check ALL capacitors before I install them into any circuit.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 10:55 am 
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Poston Drake wrote:
HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them.


This precaution may seem silly to some, but defective new electrolytic caps do indeed exist. More often it is not that they are totally defective, but rather that they may give erratic symptoms or take an unusually long time to properly reform, while bringing their voltage up slowly and monitoring/limiting current with a vintage R-C bridge-type metered cap tester such as a Sprague Tel-Ohmike, which in some cases (even if they do eventually reform) might lead one to consider whether he really wants to install them into a piece of high-quality radio/audio gear which he is restoring. And even more especially, when investing the additional labor to "restuff" them into original cap shells/cans.


I'd like to add that any of the Sencore Z-meters (LC75 through LC103) that test for leakage work as well. For me, a simple ohmic check was all that was needed to find a bad NEW "MIEC" capacitor - resistance across it was less than an ohm - new. The LC102 confirmed it, and no reforming was possible, as the current wouldn't drop below a few hundred milliamps - it was just heating up the cap.

And so ended my adventure with no-name capacitors. I was already a skeptic - and with Mouser joining the Panasonic distributorship in the last decade, prices at Digi-Key fell for most electrolytics and film capacitors I was already buying, so a win-win, less expensive brand name stuff and free shipping to boot. (to wit: 0.047uf, 630V Panasonic caps just 19c in 100/qty....) Yes, axials are not available, but the radials do just fine. I do miss the clearance prices I got at Allied Electronics two years ago - axials (Mallory and Illinois Capacitor brands, absorbed by CDE) for just pennies each, although most were only 400V types. Still, 37 dollars for 1400 capacitors, shipped.

What kills me is the availability of hordes of no-name capacitors at dozens of online vendors that have no datasheet. Are the caps that bad? No QC testing, or is it greed? Further, the datasheets you do find are either worthless (no power factor or ripple current listed) or are "fake" or copied without care. I've seen a "CSE" datasheet for some film caps that is a clear copy of Illinois Capacitor's MWR series - right down to part number breakdown, despite CSE's vendor showing different part numbers and not offering the same values/voltages...CSE being a "close by association" name vis-a-vis "CDE", a brand name that we all trust.

If I'm gonna take my time to repair or restore an item, why would I risk it with some no-name part, when dollar-for dollar I can put a name brand in the radio or TV and never look back? (Full disclosure: I also repair some industrial electronics, as a side job - refrigeration control boards, switching power supplies (mattress industry), and just recently, some old 90s motherboards for CNC controllers..and capacitors are a huge failure item there too...)

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jul Wed 26, 2017 1:19 pm 
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I recently refurbished 3 70s Pioneer receivers. This involved over 200 electrolytics. The replacements were all Nichicon from Mouser. One cap was bad right out of the gate. Out of curiousity, I opened it up and found a mechanical problem that suggested that others from the same type and lot could also fail. Since such things are statistically rare, I just wrote it off and moved on. If I were to do 3 more similar sets, I would not screen all the caps before installing.

With tube stuff---where bad caps can do more damage---I always test electrolytics, but this is done in initial startup in the set....meter on the B+, input coming up slowly with a Variac,etc.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Aug Thu 03, 2017 9:07 pm 
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HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them...
To date, I've never found a dead new one... however, as a matter of course, I always check and reform new electrolytics on a Sprague Tel-Ohmike TO-6A, watching the charge and forming current go down to a very low level (depending on capacitance.)
Cheers,
Roger

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Aug Thu 03, 2017 11:53 pm 
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I normally test from 10 to 50% of electrolytics I get, depending on the source and manufacturer. Can't remember the last time I found really bad ones (like shorted or leaky), but it has happened.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Aug Fri 04, 2017 2:25 am 
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Johnnysan wrote:
I normally test from 10 to 50% of electrolytics I get, depending on the source and manufacturer. Can't remember the last time I found really bad ones (like shorted or leaky), but it has happened.

I agree with Johnnysan. A really bad one is extremely rare, although they do exist. More common are some that take an usually long time to reform, or give erratic symptoms during the reforming process. Even if they eventually reform and test OK, this is a "red flag" for possible future problems.

Also agree with Johnnysan: If you have purchased a sizeable batch of electrolytics, same source and manufacturer and same value/rating, have tested a representative sampling of them and all test good and reform properly, little reason to test every single one of them. But even so, if they have been on your shelf for several years then the situation is different.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Aug Sat 05, 2017 1:33 am 
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I also test every new component before installation. Some years ago, I ran into some new electrolytic capacitors which had rather high power factors, but everything that I have tested lately has been O.K.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Sun 03, 2017 5:46 am 
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I have seen a counterfeit electrolytic out of China that had used, salvaged caps inside with a wire soldered on them to extend the PC leads to make a radial 'lytic.
In the one I saw, it actually had a 470 mfd 35 VDC cap in it, but he casing was marked 1000 mfd 50VDC.

So I check all caps, 'lytic or not and all other parts before installing. Over the 45 years I had my business I saw enough DOA parts that testing on any replacement part was mandatory before installing.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Wed 13, 2017 10:46 pm 
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HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them. In the last 6 months, I've put into 2 radios new electrolytics that were bad. Turn on the radios for the 1st time after rebuilding--terrible hum, as if you never took out the old 'lytics--tack in another new 'lytic loosely, all becomes well, and that bad new 'lytic is clipped out, & thrown in the can...which is a shame...So from now on I'm checking my new caps before installing them.

Yes, I agree. I had it happen recently with a batch of 20 caps I had ordered. But, I test (to one degree or another) every component before I install it. Time consuming but worth it.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Thu 14, 2017 3:58 pm 
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WPE9IJF wrote:
But, I test (to one degree or another) every component before I install it. Time consuming but worth it.

+1 to this. Yes, it is time consuming. But not nearly as much so as troubleshooting for a defective "new" component in a newly recapped radio. Especially if your previous work involved "restuffing".

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Thu 14, 2017 10:17 pm 
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Inasmuch as I have almost never found a "bad" new part yet in over a 100 old radio restorations and several amp builds.. I choose to go with the odds.
If I ever DO actually get a bad new part and put it in service ... and then if it fails.... The amount of time and effort to locate and replace it is minuscule compared to testing everything when it arrives or at the time of installation.
But in a way.. I do have to "test" my precision resistors before installing them because the colors are so darn hard to distinguish... yuk.
I can't tell brown from red from orange on those things.

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