In my youth, the most common caps I replaced were 'lytics. Next in line were wax coated tubular paper caps. Only once do I remember replacing a "black beauty". That was because it had a crack down on side of it, which tells me that it was likely bad, and if it wasn't, I knew it needed to be replaced anyhow, before it did absorb moisture and fail. I did replace a few ceramic disks, but that was bcause I broke them while unsoldering other stuff.
I can totally understand what you are saying. However, I am not so sure about whether I would want to replace all of them in certain parts of a radio or tv. Here are my thoughts on this.
Lets take my Hallicrafters SX-99 (which I paid for but dont have yet). That radio is 62 years old. (made in 1955). The seller said it works fine, (and I was sent a video of it working. I did detect a very slight hum. (But the video's audio is not the greatest).
So, as soon as I get it and play around with it, I will replace the electrolytics in the power supply and any other 'lytics (if there are others). Even if there is no hum, I'd replace them, just based on age.
However, this is a working radio. I ask myself if I really want to replace all the other (small) caps. [Then I say to myself.... if it works, dont fix it].
But, I know there are caps in specific circuits more likely to fail, than in other circuits. Those would be caps connected to the high plate voltages, especially at the audio output tubes and in the power supply. I also know that if those short out, they can damage other parts, such as tubes, resistors, and more. So, I would likely consider replacing those. I might even consider replacing ALL the caps in the power supply, and all audio stages, and feel safe doing that, since those caps are not real critical as far as affecting the overall performance of the radio, even if the new caps are a little different in their capacitance.
Where I do NOT feel comfortable changing them, are in all RF and IF stages. The reason is that I know that a cap/coil circuit plays a big part in the inductance, which affects the radio alignment. I am not equipped to align the radio coils, and would prefer to leave them alone, as long as the radio is getting good reception.
I also know that those RF and IF stages do not operate on as high voltages as do the audio output stages. So, once again, I ask myself, "Do I really want to risk throwing this radio out of alignment, when it's working fine, and knowing those caps are not as likely to fail".
I answer myself "Probably not".... (As long as the radio is working well, dont screw up a good thing.... Then too, if the caps in those circuits are .05 or .003, I WANT a .05, not a .047. (And it seems that .05 is no longer made).
So, if I'm satisfied with the performance of this radio, I will replace the 'lytics regardless. I may also replace all caps AFTER the volume control, as well as all caps in the power supply. But I will likely NOT touch any caps in the RF and IF stages.
That's my thinking on all of this right now. Not just for this radio, but anything..... Now, if it were simply an audio amplifier, I'd likely replace all the caps, because audio is not all that critical.
To quote a good friend of mine, "There are only two kinds of paper dielectric capacitors. Those that are bad, and those that are going to be bad."
The paper caps in the RF and IF stages are bypassing and coupling capacitors. They need to be changed as well.
"Working" is a subjective thing. Known failure prone parts are just a time bomb waiting to convert working to not working. And possibly causing collateral damage when they fail.
Back then, they liked "round numbers." Then the industry standardized on incremental changes. As a matter of course, .02 now is .022, .03 is .033 and .05 is .047. Unless you're playing with tuned audio filters, the difference is statistically zero.
-- Jeff-1.0 wa6fwi http://www.foxsmercantile.com
No
housed in a glass cylinder, similar to a common 3AG glass fuse. Inside was some chemical solution. When a few volts of DC was applied, electrolytic action caused one end to slowly turn dark, thus indicating the amount of time that the DC was applied. Sorry, but I couldn't find the vendor or an equivalent online. When the required maintenance was performed, the indicator would be replaced as it could not be reset. "
They used something similar in time lapse video recorders. When those links or whatever went, you are required to replace the video head.
YOU ask around about the radio. There's a point where capacitors got better, so the bypass capacitors may not need replacing. With some old radios, it even happened during the production run, so the specific radio early in the run may need the capacitors replaced, while later the capacitors were better and don't need replacing.
SOme specific radios may have some problem that is common, so there'll be warnings "change this capacitor right away, or else it may take other things with it". Those may not be that the capacitor is likely to fail, but that if the capacitor fails, it can do damage.
SOme vintage and/or models of radios suffer because the capacitors inside the IF transformers go bad over time. Asking about the radio will uncover that sort of thing.
There were periods when a brand of capacitor came along and got heavy use, only later it's discovered that they don't have long life. It's those that are the issue, not "all capacitors".
But those low value capacitors are the ones least likely to go bad. Any capacitor can go bad, but generally this is about old types of capacitors. Nobody uses paper capacitors anymore, but those were used for audio coupling and bypass capacitors decades ago, and not only can go bad, but have limitations based on how paper capacitors are made.
Small value capacitors (like below .001uF) are much more likely to be ceramic or mica, which generally are okay, at least after a certain point in time. I don't think those are included in the "change all the capacitors" except if the radio is really old, or a specific model has some known problem. Yes, if you change the low value capacitors, you risk upsetting alignment or calibration, and you may inadvertently shift wiring that needs to stay where it is.
Any component can go bad. This is about doing most of it all at the same time because once the radio is apart most of the work is done. And some capacitors are way more likely to give trouble.
Michael
And with names like "Black Beauty" and "Orange Drop", who would question at the time that they weren't good products?
Michael
What you are saying here is true for almost everything produced. All cars have certain common problems specific to the brand/model. Same for other machinery, and for electronics and even plumbing faucets and so on...
I would like to find out what problems are specific to the Hallicrafters SX-99. Where is a good place to look?
I'd be interested in which of the old caps were known to have "issues". or to fail. Sure, they are all old (in any tube equipmnent), and they are paper caps, which are no longer made, but I'm sure some brands were better or worse than others. And just because newer caps are made from plastics rather than paper, does not necessarily make them better. Plastics can have issues too. Not to mention that everything made today is made for a short lifespan. Considering that, if most of the old paper caps still work, 50, 60, or
70 years later, they obviuosly were not poorly made or a poor design. I always say, "New does not necessarily mean Better". Today, this is quite apparent in a lot of things. Old cars far outlast the new ones, old homes were built better than new ones, and while many will disagree, I'll take Windows XP, or even Windows 98, (I use both) any day over Windows 8.x or 10. So, often times, new is NOT better and sometimes it's worse.One thing I've noticed is that all caps seem to be a lot smaller these days. (For the same value and voltage). I'm taking a wild guess, when I figure this is because paper was thicker than the plastic materials used today. But is this really better? Thinner means that high voltages have a shorter distance to arc across, causing a short. And which of these plastics will still be good in 5 years, or 20 or 50 years? Paper caps seem to have passed the test of time. We wont know if these newer materials pass the test of time or not, until we get there.
I'm not saying any material is better or worse, because I am only guessing, but it does appear that old technology, made from things like steel, wood, brick and other natural materials, are lasting longer than most plastics. It's like when Chevy started using plastic timing gears in their engines, which soon proved to fail much sooner than the old steel ones.
So, are the newer caps really better? I dont know... I can only go with the advice of those in the repair end of the business, and that is all based on time. The manufacturers always claim they have a better product, because they want to make sales, so their words mean nothing.
When I finally do get to recapping this radio, I am still clueless what type of modern caps to use. In the old days, they were all paper caps, and it just came down to knowing which manufacturer had a better reputation. But now there are multiple different plastics in use, which makes it a lot harder to know what to use.
Everything will fail some time in the future..... It dont matter what it is. But will it be tomorrow, or 100 years from now? So, somtime in the future, every paper cap, as well as every modern cap is going to fail. But at my age, I only have to think 2 or maybe 3 decades at most into the future. After that, it's someone else's problem.
It could have been PURPLE HAZE!
I know from years of personal experience that "Black Beauties" were
*notoriously* bad. However, I always thought the Orange Drops were pretty good. Not so?
Back in the mid 60's into the 70s, I was told the black beauties were one of the better caps made. But after reading a lot of websites about caps, it now appears they have proven to be bad.
On the other hand, back then, and still now, it appears that the orange drops were highly rated, as well as being some of the most costly. Except for one poster in this thread, I have never heard anything bad about them. One of the websites I was reading said they are one of the brands to consider for recapping, but went on to say that there are cheaper caps which work just as well.
Back then, I used a lot of orange drops as replacements and I never had problems with them. I will say that I did not always like the fact that their wires come out of the bottom, since for non-circuit board applications, they were a little clumbsy to fit into some places, versus the tubular caps with wires on the ends.
The preferred values were worked out so you can fill the spaces between them with series/parallel combinations.
I've never seen mica in TV or monitor HV sections - and I can't think of any advantage from using them for that.
The whole thread is based on a bit of a generalisation - you have to apply a bit of common sense.
Generally; coupling and decoupling caps close to tubes that run hot are good candidates.
Caps that may affect tuned circuits tend to be close to small signal tubes that run much cooler.
I always thought those were oil filled, but I see I was wrong. I looked on the web too, and it appears that most of them were filled with a boric acid solution, which is not really harmful. They all had the tiny vent hole in the top, and had a large threaded mounting on the bottom, which required a sizable nut.
It's been years since I touched one of them. I only remember (vividly) getting sprayed by one of them many years ago. It was boiling hot and it hurt like hell. After that incident, I just replaced them before I even pluggd in anyting that had that type of cap. (Or put a soup can over them temporarily) They were probably the worst caps ever made.
Here is a pic I found online.
Thats all I have too, and some of it has not been used in years and may likely no longer work. I'm not looking to get heavily into this stuff anymore. My eyes are not that good anymore either. I just want a project or two so I have something useful to do indoors during these long cold midwest winters. In the warm weather I am mostly outdoors working on building stuff and fixing antique machinery. But in winter it's either stare at the lousy programming on tv, waste a lot of time reading (a lot of crap) on the internet, or do something with rewards, which means restoring some ancient electronics. I'll never fit in with the current cellphone/facebook crowd.....
-- I overheard a young guy bragging about his new Iphone. I walked up and told him I had something better, AN EARPHONE! :)
I discovered that from experience. BBs were notoriously leaky, both electrically and physically.
I never worried about the cost -- I always figured the labor to put in a good one or to put in junk was the same.
Ditto and thus the reason for my original question.
True in my case too. I also used them along with 88 mh toroidal telephone loading coils to make Mark / Space filters for radio teletype decoders --and the orange drops were very stable. (I know, I'm dating myself in this day and age of software/sound card RTTY decoders). :-)
You and me brother. You and me. ;-) As a side note, I'm still playing with RTTY and using a real machine. A Lorenz Lo-15c. ;-)
-- Jeff-1.0 wa6fwi http://www.foxsmercantile.com
On 2/4/2017 1:49 PM, snipped-for-privacy@tubes.com wrote: > Back then, I used a lot of orange drops as replacements and > I never had problems with them. I will say that I did not > always like the fact that their wires come out of the bottom, > since for non-circuit board applications, they were a little > clumsy to fit into some places, versus the tubular caps with > wires on the ends.
They are good parts. A bit over priced however. And yes, radial leads instead of axial. Can be an issue when you're replacing axial lead parts.
-- Jeff-1.0 wa6fwi http://www.foxsmercantile.com
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.