Vintage Products

Re: How-To : Replacing old caps with modern replacements

Die_Bogener — Sun, 16 Nov 2008 07:21:00 GMT

Hi,

i would like to add some comments...

Tantal caps were used a lot in the 50-70th, then they were replaced by the cheaper electrolyth types. Today they are still used in power supplys, very often as a smd part.

Tantal is very reliable, even for a very long time, they are still very good in power supply's, they have a low ESR and very good filter characteristics. They have almost no trouble with aging, since there is no electrolyth, they can resist heat and mechanical vibrations. So, it sounds like the ideal capacitor. But there is more...

If not used for a very long time (10-20 years...! ) they tend to burn and explode when used again. I found several of these exploded tantals in computer mainboards of the early 80s, just the 2 pins remained, the rest was gone... and i saw it live, it started to burn on the top and ignited more and more. It was a real fire, that was no fun at all.

I could test and reproduce this effect. If you use an old tantal ( i.e. 4.7uF 16V) and start at once with it's maximal rating 16V, it will burn like a candle. So, never start old hardware without watching it...

The next thing is: Tantal has a very bad filter character used in the signal path for audio applications. I had some old tape decks (B&O and Telefunken) for repair, the owner wanted to play and hear his own old records. I repaired the mechanical deck, replaced all other caps and the sound was original again, but so bad, it was hardly to understand, there was almost no treble and way to much bass. That's the way it was 40 years ago...

The reason was, that there were some tantals used in the sound path. I replaced them by MKS Wima polystyrene types and the sound was perfect, way beyond it's original specification when these decks were new. The sound was clear, loud and almost like todays equipment.

So, if you find tantals in the the sound path, replace them by modern types. Ok, you change the sound, it does not sound like original, but it sounds fantastic for this old hardware.

Martin

Re: How-To : Replacing old caps with modern replacements

yachadm — Tue, 14 Oct 2008 20:05:13 GMT

The single most useful tool to assist in identifying bad capacitors is called an ESR Meter.

It measures the ESR - Equivalent Series Resistance - of a capacitor - in-circuit, so you do not have to unsolder the capacitor to measure it.

Google "EVB ESR" to get to a super, affordable meter made in Portugal, by a gentleman who offers superb after-sales service. This unit is made under licence from the original ESR meter by *** Smith in Oz.

EVB sells fully assembled units, as well as kits, for those of us who like to have fun with a soldering iron.

Menahem

Re: How-To : Replacing old caps with modern replacements

BenSA — Thu, 31 Jul 2008 04:31:11 GMT

Dillen:

Found this excellent picture on Google.
There's really no signs of age to a tantal so an old and a new looks pretty much the same.
B&O tend to like using red and green ones, not that the color matters though but different brands may use different colors.
Sizes vary from apprx 3 - 6mm in diameter and height. The shown cap is 4,7uF 35V with positive lead lowest in the picture.
Martin

Thanks...I always wanted to know what those were!! Never thought of replacing them.....might be the solution to some of my problems on a particular BM1900!!!

Re: How-To : Replacing old caps with modern replacements

PCPete — Wed, 30 Jul 2008 20:05:50 GMT

Wow.

Thanks to everyone who found time to respond to this thread!

To help clarify some very good points raised, here's a summary of the ideas I really want to cover in the guide:

There will be pictures. Lots of pictures! So for newcomers who don't know an electrolytic capacitor from a constipated elephant, it should be very easy to identify, check, and replace faulty or "tired" components. (Hint : a constipated elephant is much larger and less shiny than most capacitors! I hope that helps! )

The cap stuffing (or potting) is only really suggested for large offboard metal-can type caps. It's fairly fiddly, and definitely time-consuming (compared with replacing board-mounted caps, which are a piece of cake to replace), and you don't want to be potting away with no audible result.

However, I do agree that all likely caps should be measured and replaced if they are causing audible problems. That includes tantalums (the older style tantalum caps, in the little plastic drums, are definitely a problem 40+ years on), and even some greencaps and MKTs or polypropylene caps in more recent equipment. (I'll help identify which are which).

The important thing to note (and Puncher raised this point recently) is that you don't always want to just swap out caps unless there is a really clear need to. Electrolytics tend to dry out over the decades, but not all electros do, and some never do. It can sometimes be related to a particular batch, but sometimes, you get lucky, and the caps are OK. In that case, it might be more of an aesthetic repair, where one particular component on one channel is stuffed, but the other isn't, in which case it's entirely up to you.

And if you do intend to swap out caps willy-nilly, it's probably best to be able to identify the most likely suspects before digging out a soldering iron, or you could be in for a long and tedious repair. Again, I hope I can help identify the worst offenders.

In any case, there's a lot of information to cover, and there's more than one way to pot a capacitor (pardon the pun), so hopefully I'll be able to help identify the usual suspects, as well as helping to give some users the confidence to understand which components may need replacing, how, and with what.

I'm not an engineer or a rocket surgeon, but I hope I can cover most of the excellent suggestions and requests. Keep 'em coming!

I also do a little photography, and I know a pixel from a popsicle (the popsicle is the cold yummy thing, right? ), so hopefully the guide won't be a huge, pixellated monster filled with boring text.

Thanks again to all who have made suggestions, and if you're an interested lurker, please do ask if you'd like to see something not mentioned here addressed.

This is such a cool forum. Thanks to everyone who's taken the time to respond. Keep them coming!

And stay tuned!

Re: How-To : Replacing old caps with modern replacements

Puncher — Wed, 30 Jul 2008 16:20:53 GMT

As a bit of an aside - I recently replaced the crossover electrolytics in my RL60's after twenty odd years (mine from new).

I was gutted to hear no marked improvement nor, afterward, no measurable differences in the capacitors, old or new. I must admit to being completely flumoxed, I had assumed they would have slowly deteriorated over the years without me noticing and I would hear a bright, new top-end. - I certainly wouldn't advise anyone buying old speakers to assume the crossovers might be OK - if you aren't sure, change them anyway, it isn't a huge job.

The details are HERE. - look for the pdf attached to my post.

It just goes to show you never can tell (and you certainly can't assume).

Re: How-To : Replacing old caps with modern replacements

Dillen — Wed, 30 Jul 2008 15:23:02 GMT

Found this excellent picture on Google.
There's really no signs of age to a tantal so an old and a new looks pretty much the same.
B&O tend to like using red and green ones, not that the color matters though but different brands may use different colors.

Sizes vary from apprx 3 - 6mm in diameter and height. The shown cap is 4,7uF 35V with positive lead lowest in the picture.

Martin

Re: How-To : Replacing old caps with modern replacements

BenSA — Wed, 30 Jul 2008 14:51:37 GMT

I think this is a very informative thread especially for people like me who really enjoy trying to do their own repairs. Firstly though I know what an electrolyte capacitor looks like and I can replace them but i have never heard of a tantalum capacitor? Maybe someone could post a pic of an old one and what a new replacement would look like?

Thanks

Re: How-To : Replacing old caps with modern replacements

Dillen — Wed, 30 Jul 2008 12:25:23 GMT

Nice post but I tend to disagree a bit with you regarding PCB mounted caps;
I've repaired thousands of B&O things and it's my experience that PCB mounted caps
are just as prone to failure, and maybe even more so, than the large aluminum cans.
Especially the red and orange cylindrical ones that B&O have used heavily are
given candidates. Also some of the "japanese"-type of PCB mounted caps can give
problems, I'm thinking of the ones found in f.e. Beogram CD X where a large number
of 22uF caps provide many hours of repair fun.
Also the tiny, mostly green, ones found in the Beocenter 2100/2200/4000 range are prone to failure,
here the pins seem to oxidate off, presumably because of leakage of the electrolyte fluid.
I don't do many VCR's or TV's but also here the PCB mounted caps easily count for
the majority of faults.
Die_Bogener posted a wonderful thread about the VX5000 machine and the volume of caps problems found here.
That famous capacitor used in many B&O CD decks also springs to mind - and here it
will actually have to be the correct brand and type of cap to make it work.
Fitting a modern component with "far better specs" won't do.

The large cans can be faulty, of course, but it's my experience that it's not quite
as often as many people think, at least when it comes to B&O audio stuff from
the 70's and 80's. Of course they should be checked when restoring the set and any
bad readings or signs of leakage is of course a good reason to replace them.
Large caps, well electrolytic caps in general, from the 1940's and 50's are a completely different issue though. The same goes for the wax-coated paper type that
are practically always leaky.
I like to replace them all on sight as a matter of cause.

To preserve the original look, it's indeed possible to fit a modern component inside
the emptied shell of the old one but it's a fiddly job and really only worth doing
in rare, old or specifically valuable sets.
The paper wrapping of wax/paper caps can be scanned and wrapped around
modern components to keep the innards looking original the same way.

Tantals will develop the odd fault but are generally very good components.
The pattern seems to be that if one tantal fails in a set, the others will probably
also be bad or at least marginal so it's either all stay or all go (Beogram 4002 and 4004).

Ceramic caps and polyester caps are generally very reliable components and I wouldn't
dream of replacing any of them unless physically damaged or otherwise proven faulty.
Besides, many caps of this nature works in carefully adjusted circuits and a replacement
will often require readjusting of the circuit, a waste of time and completely
unnecessary unless of course the actual component was indeed faulty.

We like photos, so please go ahead and post some.

Martin

Re: How-To : Replacing old caps with modern replacements

Jandyt — Wed, 30 Jul 2008 04:42:01 GMT

I have sent you a PM Pete.

Re: How-To : Replacing old caps with modern replacements

PCPete — Tue, 29 Jul 2008 18:22:33 GMT

Wow. Sounds like this is an interesting issue for some people.

While I can't really help with cap replacement in terms of millinery (sorry davefarr ), I can hopefully do something for electronic 'hat' replacement.

I'll post an update in a day or two (I have to find a way to post images as well as write some text). Please bear with me, I'm flat out in my day job (audio/video repair/recovery), but this will be first on my spare-time list. (You could say I have low capacity, but that would be a terrible pun ).

Stay tuned!

PCPete

Re: How-To : Replacing old caps with modern replacements

PCPete — Tue, 29 Jul 2008 18:15:16 GMT

Andrew, the problem you describe could have been caused by a number of issues.

But if the problem you experienced did disappear after turning off the unit, then the simple test will be to see if the humming reappears. If it does, then one of the possibilities could be component changes over time.

I'm not sure how old the Beosystem 7000 is... if it's a 60's or early 70's model, then that might suggest components are the cause.

But it could also be due to any number of unrelated issues. (I sound like a politician, sorry about that!). Maybe if other folks have seen the same problem you have (and if the 7000 systems were popular, other users might be seeing the same problem you describe), it would be easier to confirm.

That would include issues with the power in the house, external electrical fields, speaker leads routed in parallel with house wiring, and others more exciting and unrelated.

Unless the humming reappears, I'd hold off on replacing caps for the time being - it's a reasonably fiddly job to do (even just swapping caps without putting them inside the old ones), and it could just be one or two components at issue, and figuring out which is which could be a bit of a task.

But if the problem reappears, it's one thing you can try!

Cheers,

PCPete

Re: How-To : Replacing old caps with modern replacements

rabble — Tue, 29 Jul 2008 11:24:57 GMT

Hi Pete,

I have a Beosystem 7000 hooked up to a pair of Beovox 5000 type 6206 ( with cubes)

A while ago I went on vacation and turned off the power to the sytem, when I cam back all previous humming from the receiver disappeared.

To my ear the speakers sound good, do you think that replacing the caps (where) will make a big difference?

Andrew

Re: How-To : Replacing old caps with modern replacements

davefarr — Tue, 29 Jul 2008 06:23:24 GMT

Peter,

please go for it and post your cap replacement info. I'm an electronnics novice and before I break out the blow torch thingy to weld the insides of my failing units, any help is appreciated. When I first saw a thread on cap replacement, I thought it was a fashion statemement about hats!. As an aside, I look like a prat in a hat and once reduced a whole shop full of people in the Lake District into hysterical laughter just by trying on hats.

Re: How-To : Replacing old caps with modern replacements

wirralsimon — Tue, 29 Jul 2008 04:56:19 GMT

Please post away! It is something that quite a few of us will need to tackle over the next few years as our kit ages.

Simon

Re: How-To : Replacing old caps with modern replacements

Jandyt — Tue, 29 Jul 2008 03:37:47 GMT

Get'm on Pete!

If you make one person happy, then it's worth it. I for one would love to see a blow-by-blow account of cap replacement.
I haven't tackled it yet, but with lots of older B&O, I'm sure I will soon.

Andy T.