LCR meter question for electronics repair people.

Discussion about old PC hardware.

Re: LCR meter question for electronics repair people.

Postby luckybob » 2017-11-27 @ 03:14

gdjacobs wrote:Not the sort of maintenance strategy that will fly with anything having expensive downtime or repair cost. Sure, your car tires will tend to wear fairly evenly (unless your front alignment is bad or the weight distribution is uneven). That won't always be the case, and you should never assume so.


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Moving on...

Ozzuneoj wrote:
luckybob wrote:get a roll of the old lead type solder. Flow a bit onto each joint. remove cap, then remove solder via pump or braid.

I have lead (60\40 I think?) flux-core solder, and I do try to do this, but my technique is probably lacking. Its like the new solder won't stick to the old joint most of the time.

What do you do to prep a solder joint on an old board?


I usually run my iron quite hot for motherboards. My 50W weller does a good job. Just be patient. Honestly It is mostly trial and error. I tend to do one leg at a time and just "rock" the cap out of the board.
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Re: LCR meter question for electronics repair people.

Postby Koltoroc » 2017-11-27 @ 03:42

WTF is wrong with you people?

"Sampling" caps to judge if there might be bad ones is probably about the dumbest thing I have read in a while. This is not QC for a cap manufacturer, this is about repair and maintenance. If you already desolder caps anyway, just recap the whole thing and be done with it. Why are people so insisting on half assing repairs? You are neither saving time or money, you are merely prolonging the guesswork of what might or might not be wrong. And all that over a few cents worth of caps? Cheap Bastards indeed.

gdjacobs wrote:Not the sort of maintenance strategy that will fly with anything having expensive downtime or repair cost. Sure, your car tires will tend to wear fairly evenly (unless your front alignment is bad or the weight distribution is uneven). That won't always be the case, and you should never assume so.


If something has expensive downtime cost you should have redundancy to allow for repairs and if repair costs are high, half assing it will only compound the costs down the line. if either is a problem management is the issue, not the downtime or the repairs.

And here we are talking about hopelessly outdated and obsolete hardware we are keeping around as a hobby and a specific type of repair that costs pennies in parts and a bit of your time. That is the absolute last place where there is any reason to half ass it. If you are too cheap for a few caps or you can't live a few weeks or days without a specific piece of hardware until you have time to properly fix it, you are in the wrong hobby.
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Re: LCR meter question for electronics repair people.

Postby luckybob » 2017-11-27 @ 04:09

Koltoroc wrote:WTF is wrong with you people?

"Sampling" caps to judge if there might be bad ones is probably about the dumbest thing I have read in awhile. This is not QC for a cap manufacturer, this is about repair and maintenance. If you already desolder caps anyway, just recap the whole thing and be done with it. Why are people so insisting on half assing repairs? You are neither saving time or money, you are merely prolonging the guesswork of what might or might not be wrong. And all that over a few cents worth of caps? Cheap Bastards indeed.



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Re: LCR meter question for electronics repair people.

Postby Ozzuneoj » 2017-11-27 @ 05:07

So you two don't really care if the caps you replace on a working board actually need to be replaced? Or do you only replace the caps on boards that aren't working correctly or that you plan on using in PCs you plan to keep for a long time?

I'm not talking about fixing boards with problems while avoiding obvious repairs, like replacing all the caps... that'd be stupid. I'm talking about trying to understand if and when it makes sense to recap a board for preventative maintenance. You people can swear and be belligerent about this all you want but somewhere there's someone who would take this even farther than you that replaces caps in brand new electronics just because they don't trust that the manufacturer used fresh caps... and they would probably call you guys foolish for not doing that. At what point is it actually worth the effort? Do you even KNOW if the caps need to be replaced? What if the old caps were closer to the spec than the new ones you put on? Is it stupid to want to know?

I was asking about using an LCR meter because I genuinely want to know how this works. I'm not going to just jump on the band wagon with every outspoken "RECAP EVERY BOARD AFTER THREE YEARS OR YOU SHOULD NOT BE USING COMPUTERS!" arm chair electronics engineer on a message board and waste a ton of my free time (I have over 40 motherboards in my home that are worth using) and risk damaging or making a mistake on perfectly good boards if they don't even need replaced.

You guys can do whatever you want with your boards. Thanks for the advice.
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Re: LCR meter question for electronics repair people.

Postby Jade Falcon » 2017-11-27 @ 05:12

Takes me about 10 minutes to do most boards with a butane iron, no pump/sucker or solder wire.

Just heat up the leads and pull the cap out. Apply sone flux and put the new cap in, add extra solder if needed and clip the leads. Giving how much of this kind of work I do I always have caps laying around and I just recap anything that could need one now or soon.

Not sure what the big deal is. Its not hard at all nore dose it cost much, most boards maybe 10$ And if you use the right caps you only need to do it every 20 to 30 years. Its not like we're dealing with old tube amps tgat take funky oil or film caps that can cost a lot mote that what we yse in computers.

Just do it and be safe. Last thing you want is a house fire.

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Re: LCR meter question for electronics repair people.

Postby luckybob » 2017-11-27 @ 05:23

oh don't be silly. If the board is having cap issues, instead of replacing ONE OR TWO just do them all. Why is this such a foreign concept?

the LCR meter I bought is going to be mostly used for fixing old power supplies. Checking power trannies/mosfets & diodes. Caps generally are too cheap to frack with. If I took the time and effort to remove a 5 cent cap, I might as well replace with new ones (in old equipment).

are there circumstances where you can't get exact replacements and need to test caps? YES! Are you going to find them on a mass produced piece of equipment? NOT LIKELY. I recapped a plasma tv last year. Only one cap was visibly "bad", I replaced them all so I don't have to frack with it again!
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Re: LCR meter question for electronics repair people.

Postby Ozzuneoj » 2017-11-27 @ 05:38

luckybob wrote:oh don't be silly. If the board is having cap issues, instead of replacing ONE OR TWO just do them all. Why is this such a foreign concept?

I think we're having a miscommunication here. I've stated more than once that I'm not talking about boards with stability problems. I'm talking about boards that work fine that are "old". If I sell someone a nice old board that is fully tested, should I also recap the whole thing, given my skill level? Should everyone do this who has two hands, at least one eye and a soldering iron? Has anyone ever seen any thorough tests done where people have pulled and tested caps from lots of motherboards? In another thread here I asked if anyone had ever fixed a problem with a board by replacing caps that weren't from the "plague" era or showing obvious signs of failure and no one had anything to say about it.

Again, I have made no mention of boards with actual noticable problems, so please stop changing the subject to boards with obvious cap problems or stability issues. Thanks.
Last edited by Ozzuneoj on 2017-11-27 @ 05:40, edited 1 time in total.
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Re: LCR meter question for electronics repair people.

Postby luckybob » 2017-11-27 @ 05:39

If it isn't broke. Dont fix it.
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Re: LCR meter question for electronics repair people.

Postby Ozzuneoj » 2017-11-27 @ 05:42

luckybob wrote:If it isn't broke. Dont fix it.

Oh dear, okay. Thanks Bob.
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Re: LCR meter question for electronics repair people.

Postby dosgamer » 2017-11-27 @ 14:03

You need a good soldering iron. Motherboards often have 8 layers, maybe even more, with large amounts of copper that will suck the heat away from the solder joint. Removing the solder probably won't work. Do this instead:

  1. preheat the board. A hair dryer will work, or put it in an oven at 100°C. Get it nice and hot.
  2. set your iron to the highest possible setting (450°C)
  3. use lead solder. Lead-free has a higher melting point.
  4. put some flux on the solder joints. Flux that's meant for electronics, not something from a hardware store.
  5. don't try to suck out the solder. Just melt a large blob of solder so it covers both capacitor legs and heat both legs at the same time. Then just pull out the cap once it moves freely.
  6. if possible, get a second soldering iron and use one iron for each capacitor leg.

Recapping is stupid. Recappers are the equivalent of parts changers in the car world. You have to find out what the problem is. It's called diagnosis. If you don't do that, chances are you'll be throwing money at the thing, risk further damage and creating problems that weren't there in the first place by messing with stuff that isn't broken, and in the end the original problem will still be there.

Now, recapping something that works fine, that's just retarded.
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Re: LCR meter question for electronics repair people.

Postby Jade Falcon » 2017-11-27 @ 14:44

How is recapping stupid? Caps fail and its better to change them before they fail and cause more damage. If the caps are known duds just change them before you put the system together and have to pull it all apart to recap and fix possibility even more.

As for recapping something that works fine. That is a waist if it has good caps. If they are known bad caps that anther story. However with extreme overlooking I find my self recapping video cards that have good caps with different rated caps to push more MHZ out of them, but that's not for everyone.

And yes you need a really good iron for motherboard. a 15-25W iron will not do. 50W can work with some boards more so with a preheat but will take a wile. My iron (butane) is rated at I believe 450w and can hit temperature of 1500 degrees, ever see a soldering iron tip glow orange? And yes use the right flux, it will make clean up so much simpler.
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Re: LCR meter question for electronics repair people.

Postby Jo22 » 2017-11-27 @ 20:36

Okay, this thread really confuses me. Sure, recapping is generally good. Preferably before the device fails.
But what's so wrong about testing capacitors before a replacement ?
There's no guarantee the new ones are fine, either. Depending on where you buy them, they could be NOS parts, as well.
Also, some caps are more expensive than others. For testing purposes, it would be nice to know which caps are
still working and which are not. Once the device in question works again, someone can still think about a full recap.
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Re: LCR meter question for electronics repair people.

Postby gdjacobs » 2017-11-28 @ 00:07

luckybob wrote:jesus tap dancing christ...


I was thinking of other example vehicles...
Image
Image

I wouldn't expect the rubber on these to wear the same. You change the tires when the tread depth and general tire condition warrants it (aka you measure the condition of the tires).

Koltoroc wrote:If something has expensive downtime cost you should have redundancy to allow for repairs and if repair costs are high, half assing it will only compound the costs down the line. if either is a problem management is the issue, not the downtime or the repairs.


Not to dwell on it, but this is the classic argument between preventative and predictive (just in time) maintenance. Do you swap something just in case, or do you try to collect and use data to squeeze as much lifetime out of it without significantly sacrificing reliability? Repairing something that's perfectly functional which you know has lots of service life ahead of it is a waste of money in business, pure and simple.

For vintage computer hardware, I'm not saying it's wrong to swap all the caps. Early failure won't be a big deal. However, it's not wrong to keep existing caps in place either if you're confident they're in good shape. For instance, where boards have a mix of good series Japanese and crap caps with similar ages, replacing the junk parts while leaving the other is going to be fine 99% of the time.

Jo22 wrote:But what's so wrong about testing capacitors before a replacement ?


Precisely. In fact, testing with an LCR meter is the best way of determining if caps have failed on your board at all. Even a malfunction is not definitive as the caps are one of several contributors to unreliability (although probably the largest). Age is probably one of the poorest of indicators.
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Re: LCR meter question for electronics repair people.

Postby Ozzuneoj » 2017-11-28 @ 02:18

gdjacobs wrote:
luckybob wrote:jesus tap dancing christ...


I was thinking of other example vehicles...


I wouldn't expect the rubber on these to wear the same. You change the tires when the tread depth and general tire condition warrants it (aka you measure the condition of the tires).

Koltoroc wrote:If something has expensive downtime cost you should have redundancy to allow for repairs and if repair costs are high, half assing it will only compound the costs down the line. if either is a problem management is the issue, not the downtime or the repairs.


Not to dwell on it, but this is the classic argument between preventative and predictive (just in time) maintenance. Do you swap something just in case, or do you try to collect and use data to squeeze as much lifetime out of it without significantly sacrificing reliability? Repairing something that's perfectly functional which you know has lots of service life ahead of it is a waste of money in business, pure and simple.

For vintage computer hardware, I'm not saying it's wrong to swap all the caps. Early failure won't be a big deal. However, it's not wrong to keep existing caps in place either if you're confident they're in good shape. For instance, where boards have a mix of good series Japanese and crap caps with similar ages, replacing the junk parts while leaving the other is going to be fine 99% of the time.

Jo22 wrote:But what's so wrong about testing capacitors before a replacement ?


Precisely. In fact, testing with an LCR meter is the best way of determining if caps have failed on your board at all. Even a malfunction is not definitive as the caps are one of several contributors to unreliability (although probably the largest). Age is probably one of the poorest of indicators.


This is definitely more along the lines of how I maintain my equipment.

Talking about age being a poor indicator of needing to replace things... I have a nice old ~1985 RCA stereo receiver that crapped out on me the other day. Someone gave it to me last year and I hooked it up in my garage to run some old (1972 I think) Pioneer CS99s. I'd been using it for about a year, then the stereo died because the glue they used to hold things tight to the PCB became corrosive over time and finally ate through the legs of a diode. It is such a nightmare to take down though, I'm not going to bother trying to fix it now. Prior to this, the FM reception was fantastic, the clarity of the sound was impressive for its age and I had no problems with it. I've never heard "radio" sound as good as it did on this old thing. The caps were all original and there were no signs of it ever being worked on before this (too bad someone didn't chip that nasty glue off 10 years ago).

Also, my IBM 5150 (from probably 1985-87) has all original everything and works perfectly, every time I turn it on. Heck, even the old CS99 speakers I have in the garage didn't honestly sound any different after I spent a good chunk of money and time recapping their massive crossover networks (granted, they are a terribly designed over-complicated mess and aren't the best example of a vintage high fi speaker)... I did that project based on recommendations from people on message boards.

The only time I have experienced any failures or problems that were related to bad capacitors were on ones that were notoriously problematic. Failing SMD caps in an IBM M2 keyboard, leaky or swollen junk-brand caps from the plague era and bad tantalums on 25+ year old parts that haven't been used in decades.

My whole point for creating this thread was to learn what kind of meter I would use if I wanted to pull a cap from a working board and measure it to see how far away from its original spec it is. Or for that matter, for checking caps I have laying around that I've picked up over the years. I want to know more about this process. I want to know why some people are so re-cap happy, or are so vehement about caps being garbage if they're more than 5 years old... and yet no one can even give me anecdotal evidence of a device that was fixed by replacing caps that weren't obviously leaking\swollen or known to be problematic. I have a family, volunteer work, a job, many hobbies and many other things I do besides recap boards, so I want to know why I should care so much about doing so, and why some seem to think that a vintage PC enthusiast deserves to be beat senseless with a Model M for being so lazy and stupid as to not want to buy and replace dozens of caps with no evidence that it needs to be done.

Anyway, I'm still looking for recommendations for LCR meters that would be suitable for me. The Der EE DE-5000 seems like a nice unit. I read something about it not having a capacitor discharge circuit... which again, isn't something I'm familiar with. Is this a non-issue? Are there any comparable meters that can discharge caps too? I just want to cover my bases to lessen any failures\mistakes since I'm still learning about this stuff.
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