Why should someone replace ALL the capacitors on old Tube equipment?

And that brings in another issue. A lot of that old equipment is really hard to disassemble. So the effort to take it apart is greater than changing all the capacitors, so one might as well while the thing is apart.

Low value capacitors don't cost much, so replacing them all won't kill most people. Electrolytics can be more expensive, but in consumer type tube equipment, there are only a few, in the power supply and bypassing the cathode in the audio stages, maybe a few more.

It shifts with solid state equipment, a whole lot more electrolytics since transistors are low voltage low current (ie low impedance) rather than tube's high impedance. And then with switching supplies, electrolytics see much harder service since they are expected to filter AC frequencies above audio, while previously electrolytics only saw 120Hz or audio frequencies.

That's another issue. The time tracking down one bad capacitor can be costly, if you just replace all the capacitors that may be as fast or faster than figuring out which one is bad (and then another capacitor of the same vintage may go bad the next week).

Michael

Yes, precisely why I feel WW3 is a lot closer and more likely than before. This has nothing to do with my own political party preferences, or anything else, just the "person" himself (president). However, lets NOT get into a political discussion on here. Seems like everywhere on the internet has turned to politics lately. But I still do not feel safe, with the current state of the world and the current US president. It seemed a lot safer before, even though the world in general seems a lot worse than it was in the last few decades.

Trump is using executive orders for everything, that's basically ruling by decree - I don't know how that's any different to a dictatorship.

Definitely sounds like you need a plumber :)

OK

So, what are the BEST ones? For example, I am getting a Hallicrafters sx-99 radio, to recap it, what should I use for the small caps (not electrolytics)? Should I use the "orange drops", or is there something better? I'd rather spend a few bucks more and get the best.

By the way, why are all the caps now rated at some oddball figure. For example, instead of .05, it's ,047? or instead of .003 it's .0033.

Same for the 'lytics instead of 30mf, they are 33mf and so on.....

What do those look like? Are they the ones with colored dots that look like dominos? (But I think those are mica caps, if I'm not mistaken).

I remember those squarish brown ones with the leads on the bottom, those were supposed to be superior. (Silver mica, maybe?)

And the round ceramics were said to be good too.

Can you explain that. I dont understand... (I would think that a 'lytic in a power supply would only need to filter at 120hz, or would some filter at 60hz also, depending on the configuration?

I totally agree. You cant identify parts anymore and if you can, you cant get them. Especially ICs.

In the 60s and 70s, I loved to work on electronics. Mostly tube stuff. The early transistor stuff was not too bad, but as soon as they began using ICs, I lost interest in working on it.

Now, 40+ years later, I am gtting back into it, but only working on antique tube stuff, which is what i enjoy. Modern stuff is far too complicated, far too small (hard to see with my aging eyes too), and does nothing but frustrate me.

Sure, I have built every computer I have owned (or rebuilt from parts of thrown away ones). But with computers you just change boards, not individual components.

I guess going back to the tube stuff makes me feel young again!

It's a very complex issue. Your feelings are just that, yours.

I have been reading alot of websites about caps. One of them said the wax coated ones were less leaky (for moisture), than the old plastic coated ones. I am referring to the ones called "black beauties", that have color code bands on them.Yet, back in the early 70's, I knew a guy who was a retired radio-tv repairman as well as a Ham operator, and he used to say those "black beauties" were far better than the wax ones. (as well as the other plastic encased ones with the numbers on them instead of the color bands).

That's conflicting info. Yet I know that all of them are paper caps.

They call it "preventive maintainance".

Lets NOT go there.....

In all honesty, I think WE ALL LOST. But we would have lost with either of the lousy candidates we had to pick from.

Enough politics..... Lets stick to electronics. A lot more fun, and likely a lot safer too.... I'd rather get zapped by a high voltage power supply than a president with his fingers on the nuclear botton.

I could see them failing in the HV sections of ol CRT televisions and monitors. Alot of stuff seemed to fail at those high voltages.

But in radios and audio amps, they seem darn near fail proof....

Capacitors such as .047 have been around a long time. I don't know why it is such an odd value as I doubt the extra .003 would be noticable in the circuits most of them are used in. As the tollorance on most of the electrolytics are very broad I don't understand the odd values either.

The capacitors operating at 100 KHz and over are in the switching supplies that are most often used now. That puts a lot of strain on them that the old 60 Hz didn't.

I have started working on some of the surface mounted devices. It does take different equipment, but not hard to replace the bad components in most cases. You just have to invest in a stereo mcroscope for about $ 200 and a hot air rework station. For just the hobbiest there are some that have the hot air bun and soldering iron for less than $ 100. Tweezers instead of needle nose and very small solder and liquid flux. Lots of good info and how to on youtube.

I only started doing the SMD after I retired at 62.

I did put together my computers up to about 10 years ago. Then found I could get a used one off ebay for almost nothing that will do what I want. That is almost less than MS wants for some of the operating systems and the used ones have the operating system on them.

Sorta. The timer was basically a miniature electroplating bath, which used a the current flow to move ions of something, from one end of a glass cylinder to the other. A coulomb is 1 amp for 1 second and can count both electrons and ions, as in the bath. I have a box buried somewhere with the project notes which might have the data sheet. Meanwhile, I think I may have found the patent, or rather a later patent as the one I used was in about 1976: I'll dig through the citations later...

If you look at the standard values used for resistors and capacitors and inductors, you can see that they tend to be spaced in a way which creates something approximating a geometric ratio - that is, each value in the series is 1-point-something times the previous value. The higher-precision value "kit" has a total of 24 values over each decade. The common lower-precision value kit has six values (every fourth, from the 24-value higher-precision range).

The relationships aren't exact - 0.047 would be 0.046415... and some of the other "traditional" values are even further off of the geometric curve. But, that's the basics of it.

I imagine that when picking the values which would go in the lower-precision set, it was easier to just choose the same nominal values as were used in the higher-precision set, and specify a lower tolerance (e.g. +/- 10% for a cheap film cap, or +100/-20 for a 'lytic).

I'll defer to the those from the antique radio forum, who have more experience with this than me.

I have helped various friends rebuild old HF radios. I tend to replace parts involving RF with parts that have the same temperature coefficient. So, mica caps get replaced with silver mica caps. Ceramics get replaced by ceramics of approximately the same value, voltage, and tempco. Film caps are potentially a problem, but I've seen few of those in old tube radios. Bumble bee, black beauty, and orange drop caps are junk. There's no temperature coefficient involved with those, so just whatever I can find that has similar values in polycarbonate or polypropylene. This should help:

Get out your calculator and estimate the acceptable range of values based on the tolerance. For example, a 0.047uF +/- 10% cap can vary between 0.042 and 0.052uF. Therefore, a 0.050uF is just fine. Actually, if you measure the caps involved with an LRC meter, you'll find that they vary well outside of the original specifications. Just because a capacitor is marked +/-10% doesn't mean that the circuit requires the same tolerance range.

Most cheapo electrolytics are +100% -20%. So for 30uF, anything between 60uF and 24uF should work. Again, electrolytics are not that critical (or very accurate). Occasionally, there will be an electrolytic in some kind of audio filter that has to be fairly accurate. You can use the schematic to find those. The rest (power supply, decoupling, interstage audio coupling, cathode bypass, etc), can be fairly loose with the tolerances.

You won't find any MLCC caps in tube radios. You'll find them in computah equipment in the form of large SMT chip caps, sometimes with leads and dipped in epoxy: The caps are evil and fragile. They vary in capacitance with mechanical pressure and make a tolerable capacitance microphone. Touch one end, but not the other, with a soldering iron, and the temperature differential will cause internal cracking and eventually a short.

Silver mica. They're very good parts and rarely die unless you cram too much power through them as in a transmitter. Watch out for the tempco on those. It's printed on the case as NPO, N750, N1500, Y5V, Y5P, etc.

Those are called "disc ceramic" capacitors: Same warnings are silver mica.

Well, ok. I don't know of any tube radios that use switching power supplies, so yes, the highest frequency a tube radio power supply will see is 120 Hz. However, you comment was "for electrolytic caps, it seems that the newer ones have a much shorter life than the old ones did". By "newer one's", I assumed newer capacitors in newer circuits, namely switching power supplies. My guess(tm) is that newer capacitors will have the same long life as the originals (20+ years) when used as a replacement in a 120 Hz power supply.

Sigh. My collection of test equipment looks more like a museum than a working test bench. I also find myself fixing 40+ years old test equipment as I do fixing radios etc. Looking at the old stuff, all it does is make me feel old and tired.

Good luck.

Nope. The black beauty caps are di film dielectric, which is a sandwich of mylar and paper. I think they might have been injected with oil after assembly, but I'm not certain. You must have missed something in your youth as everyone I knew that was fixing TV's would break one open to see what was inside.

The preceding caps were bumble bee caps, which were oiled paper dielectric. The succeeding caps were orange drop caps which are metalized mylar dielectric.

I had forgotten that the resistors were valued at some math function. Did not know the capacitors and inductors were the same, but seems reasonable. As pointed out, almost nothing in electronic components is exact for normal circuits.

Sorry that you totally missed the point. Losing has NOTHING to do with it. The current president would be just as great of a danger to the country and world if he were a Democrat. Creating an additional nuclear threat in today's unstable world was not the smartest thing to do.

You won -- but what did you win?

A vindictive, vengeful, thin-skinned, unstable*, erratic* person with his finger on the nuclear button. Sounds like a "win" to me.

NOT!

• BTW, these two words were used by the Wall Street Journal when describing the current president.

Sorry, personal, individual "feelings" has NOTHING to do with moving the Doomsday Clock ahead. The whole world might take exception, do ya think?

In my opinion, the Black Beauties with color bands on them are bad news. Worse than wax dipped paper caps. They crack, leak oil and sometimes fail hard -- short circuit. As far as I know, all the Black Beauties with bands are oil filled.

I've seen old 50s magazines with full page ads claiming wonderful things for the oil filled Black Beauties and it sure seemed like a good idea. Steel can paper in oil caps are much more reliable than wax dipped paper caps, why not paper in oil in a plastic tube? Didn't work out that way, I don't know why. Maybe the plastic outgassed something nasty into the cap. Some of the paper in oil Black Beauties had standard numeric marking rather than bands. The paper in oil Black Beauties can be identified by a soldered lead on one side of the cap.

The second generation Black Beauties were actually OK. They used a mylar-paper dielectric which held up about as well as all the advertising promised for the first gen Black Beauties.

But the damage to the reputation of the Black Beauty had been done and the Orange Drop became Sprague's high end film cap.

** Complete bollocks.

Electro cap dissipation is lower at high frequencies cos the ESR is lower at such frequencies.

The no 1 reason for short lifspan is being sited next to heat sources, like power resistors and heatsinks.

The no 2 reason is bad manufacture by no name brands in China etc.

..... Phil