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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Feb 2018, 1:26 pm   #21
Andrew2
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Default Re: Tants

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Originally Posted by MrBungle View Post
I have learned that anything that isn't yellow and isn't less than about 20 years old should be got rid of quickly. Blue ones are especially nasty.

Yes I know this isn't very scientific.
I bought a large bag of yellow ones at a rally (many moons ago) and used them as decouplers in many projects. None of them lasted long, they went leaky or short and generally led me a merry dance.
I held on to them though, and tentatively carried on using them until they started going bang on first switch-on. Then they got chucked!
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Old 15th Feb 2018, 4:45 pm   #22
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Originally Posted by Argus25 View Post
I would totally disagree with this....unless the electrolytics you are referring to are radial through hole parts or axial parts. Most modern electros are surface mount now, in most modern gear. This is a very big problem.
This is a vintage radio and repair forum Hugo, so I would have thought it was taken as read that I was referring to though hole components rather than surface mount.

Regards
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Old 15th Feb 2018, 4:55 pm   #23
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Default Re: Tants

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Originally Posted by Andrew2 View Post
I bought a large bag of yellow ones at a rally (many moons ago) and used them as decouplers in many projects. None of them lasted long, they went leaky or short and generally led me a merry dance.
I held on to them though, and tentatively carried on using them until they started going bang on first switch-on. Then they got chucked!
That's probably why they were selling them at a Rally
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Old 15th Feb 2018, 7:04 pm   #24
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Default Re: Tants

Tantalums - whatever colour - don't age well, and should be treated with the same degree of intrinsic suspicion as classic 'waxies'.

Assume they're guilty until proved otherwise!

This applies even to the cylindrical metal-cased 'mil-spec' ones: they're a known issue in things like the Clansman PRC320 power-supply [module-5] and associated PLL/ramp-generator, where their leakiness can put a nauseating 'warble' on your SSB signal or flip a CW signal well-outside the receiver passband on a random basis. While you can still source replacement tantalums [with associated NATO stock-number] for around 80 each! the smart money replaces them with current-production generic 130-centigrade-rated wire-ended electrolytics which do the job just fine.
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Old 15th Feb 2018, 10:57 pm   #25
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Default Re: Tants

My first Tek 465B had one of those wet tantalum "milspec" units in it across the 55v line. Had a massive hole in the side of it. Replaced with electrolytic of course. Think RS wanted 22 for that tiddler.
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Old 15th Feb 2018, 11:57 pm   #26
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Hi

From memory, say 30 years ago, I don't remember seeing many catastrophic failures of tantalum bead caps. It would seem the failures are linked to ageing coupled with being operated close to their voltage rating.

The surface mount tants seem to have a good reputation for now but what will they be like in the next 20 to 30 years? I guess this is all academic really since it's well past the expected service life of most equipment.

I also recall reading about similar failures with certain monolithic ceramic capacitors, also connected across supply rails. Are these generally known for being problematic or could it have just been an isolated case?

Regards
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Old 16th Feb 2018, 12:02 am   #27
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Default Re: Tants

The SMD ceramic MLCC capacitors are pretty nasty. If you hand solder them particularly or they become fractured which doesn't take a lot of effort, they can go short. I found this out on a board I did recently that I hand soldered. Stuffed it on my PL154 with 2A limit and it blew the thing off the board after about 3 seconds. Kemet 0805 100nF jobby.
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Old 16th Feb 2018, 1:20 am   #28
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Default Re: Tants

Those ceramic SMDs go pretty loud.
The example I have got scared its owner off.
He let me have a go at blowing myself up.
I just cleaned it up and fitted a new fuse. It worked again.
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Old 16th Feb 2018, 2:21 am   #29
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Default Re: Tants

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Originally Posted by Philips210 View Post
This is a vintage radio and repair forum Hugo, so I would have thought it was taken as read that I was referring to though hole components rather than surface mount.
But the remark I replied to was about replacing Tantalum capacitors with electrolytics wasn't it ?

I don't see many (if any) Tantalum capacitors in vintage radios, either valve or transistor radios, but there may be some very late model transistor radios that have them. In fact, in my extensive vintage valve and transistor radio collection, not a single one of them has a Tantalum capacitor in it. So I would have to have been psychic to conclude we were just talking about through hole parts in vintage radios only.

Tants are mainly used in other newer gear mainly, test gear often, and they come as either surface mount or through hole. My 1990's vintage 2465B scopes for example have a mix of through hole, surface mount tants & through hole & surface mount electros. Most vintage Tek lab gear of the generation before that uses bead tants (unreliable like the one I posted a picture of)

Whenever I see the surface mount electros, I replace them with surface mount Tants to avoid the electrolyte leakage issues they have. I would never go the other way and replace surface mount Tants with surface mount electros.

Hugo.
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Old 16th Feb 2018, 3:31 am   #30
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Default Re: Tants

German manufacturers such as ITT/SEL and Grundig started using those drop tantalums from the mid to late 1970's. I think that actually classifies as vintage already.

Contrary to what I read here, they aren't always reliable in the signal path either. I've had a Grundig preamp cracle and rumble similarly to what a faulty transistor would cause, which turned out to be caused by a tantalum cap.

Last edited by Maarten; 16th Feb 2018 at 3:37 am.
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Old 16th Feb 2018, 4:06 am   #31
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Default Re: Tants

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Originally Posted by Maarten View Post
German manufacturers such as ITT/SEL and Grundig started using those drop tantalums from the mid to late 1970's. I think that actually classifies as vintage already.
Yes you are right. I first started to see bead Tants in European made Audiometers in the mid 1970's. By about 1983 surface mount Tants started to turn up in items like Seagate disk drives, possibly earlier. I first saw a video camera, made with nearly entirely surface mount parts in about 1982 or 83. The JVC GX-88, some of the parts still through hole. Surface mount is old now. But I didn't see the surface mount electro until the late 80's or early 90's and these are the greatest curse of all, yet very popular in modern electronics.

So I guess now, we can call them vintage as the term generally applies to something over 30 years old.

( I also remember those ITT Tants, but they seemed ok..at the time)
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Old 16th Feb 2018, 6:03 am   #32
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Default Re: Tants

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Originally Posted by MrBungle View Post
If there was one across both rails that sounds like a design flaw.
(EAI1000 Analogue computer). I agree. There are several tantalum capacitors connected between the +8V and -8V rails (these being the supply to the op-amps, etc in the unit), not from a supply rail to ground. I don't like it. That machine is a mixture of some very good design (like some of the precision analogue parts) and some very poor design (the so-called edge connector for one of the option boards was just bit of bent spring wire that never made proper contact). Looks like the thing was built to a price, alas.

As a result I replaced all the tantalum capacitors I could find on all PCBs. When the supply rails get shorted together it tends to end up with one of them at the wrong polarity wrt ground which is not good. ICs that use both supply rails and have a ground connection may get damaged by this.
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Old 16th Feb 2018, 9:46 am   #33
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Default Re: Tants

Blaupunkt were very fond of using tantalum Bead caps, at least in their car radios & stereos from the early 70s onwards. The Italian firm, Voxson, who designed and originally made the Radiomobile 103S, 104SR, 106S & 108SR Track players, also used them in those and other car stereos. IIRC, British designed and built audio equipment didn't make so much use of tants.
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Old 16th Feb 2018, 10:07 am   #34
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Re post #16 and #29, I get challenged for stating points that most people agree with, I get the impression the replies were being awkward, I can't understand it.
Quite often, I don't get answers to questions I put in threads that I start or threads that I contribute to, it seem to fall on deaf ears.

I've tried to help others over the years sharing my experiences in the repair business and have often helped out members with components and information. I like to give credit to members' efforts and recognise the high standards of restoration that can be achieved. I planned on posting many more experiences of the repairs to vintage equipment but I'm not so sure now.

I have also been very grateful for the help from some members and moderators but now I don't honestly know why I bother posting messages on this forum, I am beginning to get very disillusioned with it. Maybe there aren't so many active members these days compared to 10 years ago.

I am going to step back and consider my future here.

Symon
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Old 16th Feb 2018, 10:32 am   #35
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Default Re: Tants

This is my fault. I should have made it clear that I was referring to vintage tantalum bead capacitors from the 70's/80's with particular reference to the 1977 Skantic tv I'm working on at the moment.

I would certainly not trust these over good quality electrolytics.
Cheers,
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Old 16th Feb 2018, 11:06 am   #36
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Default Re: Tants

Quote:
Originally Posted by Argus25 View Post
Quote:
Originally Posted by Maarten View Post
German manufacturers such as ITT/SEL and Grundig started using those drop tantalums from the mid to late 1970's. I think that actually classifies as vintage already.
Yes you are right. I first started to see bead Tants in European made Audiometers in the mid 1970's. By about 1983 surface mount Tants started to turn up in items like Seagate disk drives, possibly earlier. I first saw a video camera, made with nearly entirely surface mount parts in about 1982 or 83. The JVC GX-88, some of the parts still through hole. Surface mount is old now. But I didn't see the surface mount electro until the late 80's or early 90's and these are the greatest curse of all, yet very popular in modern electronics.

So I guess now, we can call them vintage as the term generally applies to something over 30 years old.

( I also remember those ITT Tants, but they seemed ok..at the time)
The Thorn 2000 colour TV from 1967 used quite a few bead tants as did many other British colour tellies.

John
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Old 16th Feb 2018, 1:37 pm   #37
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Default Re: Tants

Quote:
Originally Posted by Philips210 View Post
Re post #16 and #29, I get challenged for stating points that most people agree with, I get the impression the replies were being awkward, I can't understand it.
Quite often, I don't get answers to questions I put in threads that I start or threads that I contribute to, it seem to fall on deaf ears.
Symon, I agreed with you on post 16 , you were talking about through hole parts, and I was remarking on surface mount, so when the wires were uncrossed we are in agreement, no challenges.

So through hole tants (especially bead types, if old) are better replaced with through hole electros. But probably, surface mount tants are better either left alone or replaced with surface mount tants, and in my view at least, surface mount electros should be avoided. The trouble is, they are cheap and widely used and they are taking down a lot of equipment, making repairs difficult, as time goes by.

Often remarks I make get ignored too and it happens a lot to many, so you are not alone, I think its just the way forums work. I hope you keep posting.

Hugo.
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Old 16th Feb 2018, 1:59 pm   #38
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Default Re: Tants

Blue (or any other colour) tants have - so far as I'm aware - always been trouble if you don't use them properly. Back in my Marconi days as a student and then young design engineer in the late 70s and early 80s, the internal 'preferred components' catalogue had a warning printed in bold about these capacitors. It said: 'Not to be used across circuitry with a source impedance of less than 1.5 ohms'. What this meant was - 'don't use as supply decoupling'. Good advice indeed, and I've followed it all my years as a design engineer - don't do it, despite what the manufacturers might say.

Age (and lack of use) certainly make them worse, but they were bad news from the beginning. I can still see that warning in the Marconi 'Preferred Components' catalogue and I think of it every time I snip one of the wretched things out - at least if there's anything left of it other than charred remains.

Les Lawry-Johns was dead right and so was the person responsible for the warnings in the Marconi catalogue!

Best regards,

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Old 16th Feb 2018, 2:16 pm   #39
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Default Re: Tants

Quote:
Originally Posted by Philips210 View Post
Re post #16 and #29, I get challenged for stating points that most people agree with, I get the impression the replies were being awkward, I can't understand it.
Quite often, I don't get answers to questions I put in threads that I start or threads that I contribute to, it seem to fall on deaf ears.

I've tried to help others over the years sharing my experiences in the repair business and have often helped out members with components and information. I like to give credit to members' efforts and recognise the high standards of restoration that can be achieved. I planned on posting many more experiences of the repairs to vintage equipment but I'm not so sure now.

I have also been very grateful for the help from some members and moderators but now I don't honestly know why I bother posting messages on this forum, I am beginning to get very disillusioned with it. Maybe there aren't so many active members these days compared to 10 years ago.

I am going to step back and consider my future here.

Symon


You are not alone Symon.

It happens to me all the time, perhaps its because I post too much.
I don't really mind being ignored, I talk to myself anyway, but I do get sick of certain members who jump down my throat with sarky one line answers at the slightest of opportunities when I am a little off beam.

I just reckon they have a different purpose in life, mine is simply to enjoy life, the rest, if they don't like it can suck it up.

I know I am no longer perfect, but I'm working on it.

Sorry, Mods, off topic but Symon and I have something to say too.
To get almost back on topic of steaming tants, La Plume de ma TANT !
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Old 16th Feb 2018, 3:14 pm   #40
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Default Re: Tants

This thread is starting to ramble and a few confrontational posts have been made, so the mods think it's time to close it.
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