Why Orange Drops?

[K1ZJH]

Metal oxides and are much more stable than carbon
comps. If you just replace caps and don't check the resistor values it will end
up biting you in the end.

Hammarlund switched over to disc ceramics at least as early as the HQ-140
for coupling and bypassing. 1kV discs are cheap and available.

I'm not sure ESR is a valid measurement for mylar or disc ceramics, since most
ESR meters are using 50 or 100 kHz for measuring ESR.  I'd expect their internal
reactive losses to be more of a concern, and that means making
impedance measurements in the HF ranges they'll be used for.

I'll restuff caps in radios that are early and rare enough to warrant the time and
attention.

All IMHO.

Pete

[K3ZS]

Metal oxides and are much more stable than carbon
comps. If you just replace caps and don't check the resistor values it will end
up biting you in the end.

Especially with old National receivers!

[w3jn]

I'm not sure ESR is a valid measurement for mylar or disc ceramics, since most
ESR meters are using 50 or 100 kHz for measuring ESR.  I'd expect their internal
reactive losses to be more of a concern, and that means making
impedance measurements in the HF ranges they'll be used for.


All IMHO.

Pete

W4AMV used a vector network analyzer from 0-100MHz to measure the ESR in his post above.   I've performed similar measurements with a HP3577A VNA on various capacitors, including ceramic disks.  The limiting factors are the lead inductance (which is really independent of the construction of the capacitor) as well as parasitic capacitance to ground.  In the latter case, tubular caps are much worse than ceramics because ceramics have a much smaller surface area, and the two capacitance "plates" are symmetrical, so they have common-mode parasitic capacitance to ground as opposed to tubulars which exhibit a much higher capacitance to ground from one side or the other due to the outside foil.

[ke7trp]

Hi. The test you performed was on a 100 Volt capacitor which would not be used in the HRO 60 we are talking about here.  In that radio the cap ratings on mine where 400 Volt or 600 volt.  Had you tested a new modern 600volt orange drop, the test would have been at least more interesting. I have a box of 100 volt and a box of 600 volt Orange drops and physicaly, They are very different. In fact, Nothing is the same other then the color.  There are also three main versions of the Orange Drop from my supplier.  The 715P, the 716P and the standard PS.  Various differences there are 5%, 10% and 5% with copper lead.  I use 715p and 716P most of the time.

I dont think it matters on the HRO either way, but I am paying close attention so I can learn more about caps...

C

Great info, Its to bad its for a 100Volt device.

C

Agreed, its not a valid test. In any case "work to xx MHz" is also not a valid argument.

Not sure what you imply... "is not a valid test". I could bias the unit to 100 V, and re measure its Z vs. frequency. So, what is invalid? As far as work to xx MHz... yes, you would need to investigate if this actual Z vs. frequency is compatible with the remaining network, for example, a series R of 5 ohms is not negligible if I am matching to a 1 ohm device.

[kb3rdt]

Anyone know anything about the American Capacitor Corporation?  Looks like  they make caps in the US of A. and  not hand rolled, bees wax and paper sonic superiority stuff. The first distributor I checked will accept orders of $30 or more.  I may go out on a limb and buy some of their stuff  (if I can) just to avoid filling the HRO-60 with Chinese parts. Yes, I know this makes little difference in the big picture but at least I won't be thinking about China every time I turn the big tuning knob.

http://www.americancapacitor.com/

pictures

http://www.americancapacitor.com/case.htm

or maybe these guys

http://www.filmcapacitors.com/

I can't bring myself to re-stuff caps. Bill and Don are some kind of restoration heroes for doing it.


this ones I shot gun shells

[WA1GFZ]

I have a bunch of those caps. I've never had any problems with them. Note, anything with a mil number should be a good part that was built to a mil spec and test method.

[WD5JKO]

Those Poly caps from American Capacitor are nice! ESR in milli-ohms at 100 Khz...

http://www.americancapacitor.com/vcover.htm

Of course we might find out that they too outsource from overseas...

I have used some cheap Polypropylene Caps from Mouser at HF in bypassing. On my Central Electronics 20A, at the buffer stage B+ bypass cap, there is high circulating current from the hi-Q L-C tank. Here the bypass ESR is critical and has a profound effect on stage gain and linearity. When using the Polypropylene cap (.005 uf) the gain went way up. I had to insert a 2 ohm resistor in series with it. That was too much, and I ended up with three 2 ohms in parallel. This suggests to me that the cheap metalized Poly caps from Mouser have an extremely low ESR, suitable for use in low impedance bypassing, even at RF up to 10 Mhz or higher.

Aren't orange drops available in multiple flavors? I mean polyester, polypropylene, etc.

   

Jim
WD5JKO

[K1ZJH]

I'm not sure ESR is a valid measurement for mylar or disc ceramics, since most
ESR meters are using 50 or 100 kHz for measuring ESR.  I'd expect their internal
reactive losses to be more of a concern, and that means making
impedance measurements in the HF ranges they'll be used for.


All IMHO.

Pete

W4AMV used a vector network analyzer from 0-100MHz to measure the ESR in his post above.   I've performed similar measurements with a HP3577A VNA on various capacitors, including ceramic disks.  The limiting factors are the lead inductance (which is really independent of the construction of the capacitor) as well as parasitic capacitance to ground.  In the latter case, tubular caps are much worse than ceramics because ceramics have a much smaller surface area, and the two capacitance "plates" are symmetrical, so they have common-mode parasitic capacitance to ground as opposed to tubulars which exhibit a much higher capacitance to ground from one side or the other due to the outside foil.

JN

Isn't ESR usually a spec that shows a series resistive loss in a capacitor at a particular
frequency, the same as the internal resistance for a (battery) cell? Effective Series Resistance...

If you're measuring parasitic capacitances and inductances, where does the "R"
component for ESR come from?  

I always understood ESR to be purely resistive component, with power loss.
Reactive components shouldn't introduce power (heat) loss.

A few searches for ESR yielded this:

In a non-electrolytic capacitor the metallic resistance of the leads and electrodes and losses in the dielectric comprise the ESR.

I meant to say "resistive losses" instead of reactive losses in my first post.

Pete

[K6JEK]

We've Got Yellow caps and Blue Resistors: (Sung to the tune: He's got tan shoes and pink shoe laces)

Tom, N0JMY, of Hayseed Hamfest is pursuing American made caps.  ESC/Westech does have distributors so maybe this will work out.

http://www.hayseedhamfest.com/
http://www.filmcapacitors.com/

They might be yellow, though.  I don't know.  Someone said bright colors make Carl dizzy. They make me dizzy too so I'm hoping for white, not yellow. What's with yellow? Who came down from the mountain and said from now on all capacitors will be yellow or orange?

Dave at justradios didn't seem as interested in chasing down US caps maybe because he's Canadian but he has started stocking new, not NOS, made in USA carbon comp resistors. I have a big stock of blue metal films and a pile of NOS carbon comps with the emphasis on Old but I'm thinking about these resistors. They aren't blue.  Maybe I'd trust them more than my ancient ones.

http://www.justradios.com/reskits.html

ASC caps are advertised as Made in USA on some cap site. They do have a facility in Nebraska. However, ASC stands for American Shizuki Corporation of Japan. Allied has them in their line card but the Allied website is down so I don't know just what they offer.

http://www.ascapacitor.com/

--------

... a polka dot vest and man oh man

[KM1H]

Carl, what do you use to replace leaky caps in an HRO-60 or 50?  Do you test disc ceramics?

I have to admit I assume paper caps are bad,  micas are a 50/50 proposition and ceramics are good. Is it time I revised my biases?

I use discs on most of mine unless Im restuffing using those yellow and brown film caps and with 30's radios Im rarely pushing them above 20M. For audio stages I use whatever is handy and cost effective when values and voltages are high. Ive not fallen into the audiophool myth of piezo effect in discs at least at any power level even an early Super Pro can generate. Even my Scotts have discs in places.

I do not care for the Yellow tubular caps.  Some of them are polorized and being a rookie, I have to look over the schematic if its not obvious as to wich way the cap goes

Unless you use them above 20M or so the inductance is so low in say a .01/400V that you dont care how they go. It was a carry over from the old paper caps that actually used the metal foil as a shield between stages or between grid and plate. Some 30's radios will oscillate with modern caps but its simple enough to put 1/2W 10-20 Ohms right at the grid terminal and 100 Ohms at the screen pin with a disc bypass across both sides of the screen resistor, use carbon only, either kind. All it does is to brute force neutralize and oscillation suppress those old tubes with long internal leads.

Let me know what would be useful to measure.

The 400 and 600V ones most use in .047 and .1.  Simulate the actual lead lengths used in radios including the associated wiring. The radios are full of stray L and C that must be considered.
By not valid I was referring to the small physical size with 100V caps.

I'm not an audio phool so don't any of youse jokers jump on me about this!   
I didn't believe it at first but it's true and does make an improvement in noise.

If that happens they are poor choices for that particular circuit.

They are not cheap like a disk but you get what you pay for they have a better tone to audio then others they say. But I think the frequncey so low or high we can't even hear them but you use film cap. looks like yellow shot gun shells.

Pure audiophoolery and there are several sites devoted to debunking them

Oh, yea, for what it's worth those white tubular caps are quite often early generation mylar dialectrics and usually dont go bad. You may want to remove 1 and bust it open to see what the dialectric is.

HP and others used a film Black Beauty in the 50's and all the ones Ive tested in gear or NOS are still perfect. They have red lettering.

And if you're old like Carl, bright colors make you dizzy. 

I like to be dazzled by young blonds and readheads, not bluehaired old cows

Old mica caps bear watching, too.  Disc ceramics seem to hold their values, but I have had quite a few of these to short out (that's why I use two in series for the blocking cap between plate and mechanical filters in my 75A-4).

Micas are going leaky left and right the past 10 years or so and getting worse, even NOS of the sealed dipped variety. Its a silver migration issue Ive been told by a ham chemist. Early dics were also a problem into the 60's. National got stuck real bad by CD with .1/50V in the first run of the HRO-500 and I replaced literally thousands while there as they were used everywhere. Later the .01's at 500V used in the NCL-2000 and elsewhere started going leaky or intermittent....they are all black discs. Ive also replaced a lot of tubular and dogbone ceramics, especially in Collins and some National. Be careful as some are used for TC and its pretty hard to find some TC value replacements.

I tend to stay with carbon comps for anything that handles considerable power, since I have found the newer film resistors to be delicate, often opening up at a relatively slight overload or an accidental short with a meter test probe.

I tend to do the same as Ive thousands of NOS and long lead used ones that have been staying well within tolerance. However Ive had to repaint many of the old dogbones using whatever I had that came within tolerance of what I needed; I figure after 60-80 years they are thru drifting.
Lately Ive been using the new Ohmite OX/OY family when a 1-2W carbon replacement is needed. They seem indestructible even in parasitic suppressors and as RF swamping resistors in older Alphas. etc. Available at Mouser of course.

Anyone know anything about the American Capacitor Corporation?
I can't bring myself to re-stuff caps. Bill and Don are some kind of restoration heroes for doing it

Dont know anything about ACC but Ive been restuffing for at least 30 years and do them regularly for customers on high end ham and consumer sets as well as selected ones of my own. I know several who enjoy it so much they even do it to AA-5's that they own and a few do it to vintage TV's.

http://www.justradios.com/reskits.html

Their basic cap kits are all no name Chinese crap as you find at hamfests and radio shows. There have been many reports of failures over the forums and Ive stayed far away from them. They do have some HV 'lytics of 500V and up Ive been tempted to sample as they actually have brand names but Ive no experience with them. I tend to stick with what I know works.

OK, Im through for now having started at the top and worked down so excuse some duplication that others already addressed....Im to lazy to edit

Carl

[w3jn]

JN

Isn't ESR usually a spec that shows a series resistive loss in a capacitor at a particular
frequency, the same as the internal resistance for a (battery) cell? Effective Series Resistance...

If you're measuring parasitic capacitances and inductances, where does the "R"
component for ESR come from?  

I always understood ESR to be purely resistive component, with power loss.
Reactive components shouldn't introduce power (heat) loss.

A few searches for ESR yielded this:

In a non-electrolytic capacitor the metallic resistance of the leads and electrodes and losses in the dielectric comprise the ESR.

I meant to say "resistive losses" instead of reactive losses in my first post.

Pete

You are correct, but ESR is necessarily going to be a complex number - I think since the complex portion isn't really useful the measurement is generally written as a single-term impedance.   Note that W4AMV posted a Smith chart with his analysis noting the varying impedance (that's really what it is) at various frequencies.  As you know Q factor more commonly used in RF circuits as a measurement rather than ESR, but however you want to discuss it, 5 ohms in a ~10K-100K impedance tube circuit is a negligible factor.  The self-resonant frequency of the component, although the Q is very low, could be significant however.

[WA1GFZ]

Piezo effects of ceramic caps is real. I'm not sure an audio fool would notice the effect but you hit XR7 with a lightning pulse and the value dives during the pulse. I'm seen the value drop to 1/2 during a lightning pulse. It recovers if the dielectric isn't cracked.

[KM1H]

If you got hit with a lightning pulse your own crack would be reacting too

[w3jn]

Chapter 7 of this Op Amp Applications Guide has a very good discussion on the effects of real-world capacitors and resistors, including piezo-electric effect in ceramic caps, dielectric absorbtion, etc.  None of these is all that applicable to re-capping a 60 year old tube radio, but it's interesting to see how differences in capacitor construction can affect circuit design.

http://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html

[WA1GFZ]

TNX John, I collect this stuff.

[K6JEK]

Chapter 7 of this Op Amp Applications Guide has a very good discussion on the effects of real-world capacitors and resistors, including piezo-electric effect in ceramic caps, dielectric absorbtion, etc.  None of these is all that applicable to re-capping a 60 year old tube radio, but it's interesting to see how differences in capacitor construction can affect circuit design.

http://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html

Thanks for the link. Chart from the end of chapter 7:

[The Slab Bacon]

Another interesting aspect of capacitor replacement is the values chosen.

Back in the days of crappy waxed paper caps when failure was very common. Many companies used 600v caps for some circuits because they were thought to be more "robust". If you looked at the circuit that they were working in, you find that they were running at 150v (or something like that). A real good example is : Why do you need a 400v rated cap in a cathode bypass application? ?

Also, many cap capacitance values were chosen strictly by price more than the circuit constants. After all, the actual cap tollerances ran anywhere between
+20-100%. Manufacturing tollerances were not all that accurate back then unless you bought the real high end or "special purpose" stuff.

I have given a handfull of talks at the Mid Atlantic Antique Radio Club (and others have discussed it ad nauseum) on recapping radios and selecting capacitor values for the application they will be working in. And to this day I still hear members discussung "where did you get those .0XX caps at".  If they remove something like a .05 @600v cap, they wouldn't even consider replacing it with a .047 or even a .022 in place of a .02  or using a 400v cap in place of a 600v cap when it is used for a screen bypass running at just over 100v. Geeeeeezzzzeeee......................GIVE ME A BREAK! ! !

Let's face it, a good a new .02 is still better than a bad or shorted .03..................

[The Slab Bacon]

Oh yea, just FWIW, I usually keep a szhtload of 400v "epoxy drops" around (the small ones) in the more common sizes and use them for just about everything.

Every once in a while if you go threw Mouser or Digi-Key's catalogs you will find an odd value cap that they must have special ordered and got stuck with at a very cheap price. One time I bought 500 .0123s @400v for something stupid like 15 or 20 cents a piece. I dont remember the exact price, but it was real cheap, so I loaded up on them. Sounds like a .01 to me................  

[KM1H]

I buy a lot of my stock that way from local and fleabay surplus dealers.

For a bypass the beancounters approved the lowest value that would work in many cases and the difference between a .01 and .015, .05 and .068, .1 and .14, etc are totally meaningless. On top of it they are usually all industrial grade premium types, not no name China crap.

[w3jn]

I scored several 500-ct boxes of super-dooper high quality polyprop .082/630V caps on eBay some years ago for about a half penny a cap.  I sold several boxes for $50 and still have some - but nobody wanted 'em on eBay apparently because of the odd value.  I use 'em to replace .1 and .05s.

Agree with the cathode bypasses.  I have scads of 200V caps that always go in that circuit instead of using 600 volters.

[ashart]

To add to the confusion level, one should consider that different dielectric materials result in different "temperature coefficients of capacitance" (read:  the capacitance is different when it's warmer)!

Admittedly, this is not often a big deal in typical bypass and coupling applications, but in some applications one must be on guard!

Thus, where a capacitor's actual capacitance is performance-critical, one should select capacitor types having low temperature drift.  This is generally more true of tube gear than solid-state gear, because of the difference in operating-temperature changes, and more true of any equipment subjected to greater temperature changes than encountered in the cushy environment of an ordinary hamshack.

My hazy memory suggests that mylar caps are not very temperature-stable at all, compared to some other types of caps.  Polycarbonate and polystyrene caps are much better in that regard.

The same hazy memory tells me that disk-ceramic caps are available in several types, with some having excellent temperature stability and some being downright lousy.  That is true of disk caps generally, not just the "temperature compensating" types that have specified temperature coefficients.

Tantalum caps generally have better temperature characteristics than electrolytics.

All of the above thoughts are from my pre-retirement memory of 20 years ago - time marches on - so does capacitor design - and one should carefully review current engineering literature.


-al hart
www.w8vr.org

[K6JEK]

To add to the confusion level, one should consider that different dielectric materials result in different "temperature coefficients of capacitance" (read:  the capacitance is different when it's warmer)!
...

For your viewing pleasure in case you don't have these committed to memory, the codes for ceramic capacitor temperature characteristics. Just to make this fun, there are two sets, one for temperature compensating caps and one for caps that claim no such magnificence. For years I thought an X7R was a sports car.  Imagine my disappointment.

These are just screen shots straight out of the Wikipedia article.

http://en.wikipedia.org/wiki/Ceramic_capacitor

[KM1H]

Maybe Im a bit denser than usual today but Ive no idea what those charts mean

Its no wonder TC is such a black art

Carl

[K5UJ]

For your viewing pleasure in case you don't have these committed to memory, the codes for ceramic capacitor temperature characteristics.

I don't know what this has to do with orange drops.  You study this stuff when selecting caps for loading in an output pi network, DC blocking on PA anodes and h.v. choke bypass.   It matters when the cap has to handle a lot of current on a low frequency like 1800 kc and you don't want a value drift but you don't want to use a big tx mica.  so you have the temp codes for the dielectric; the other factor though is the environmental heating which is of concern if the caps are near the tubes (DC blocking caps).   you have two classes, class I and Class II dielectric and IIRC, Class II is what you want for RF ceramic caps.   

[W2WDX]

Hi All,

I generally prefer the tubulars to replace papers. It's a fit thing mostly and the performance differences, even on the higher bands, is insignificant in my experience. I dislike OD's in general; appearance, working with them, fitting them in some cases.

I don't have the data and opinion is formed more from observation.

While we on the issue of caps, with replacing lytic's particularly in PS applications, I always stick with the original values. I can give you examples of me selling transmitters in particular to a Hammy Hambone. I had one replace the new caps in all the supplies in a transmitter and then contacted me saying he wanted his money back because the transmitter wouldn't tune, and he couldn't adjust the bias, and other issues. I had him return it to me so I could look at it, since it worked perfectly to spec when it left here.

Sure enough the cap values were all 3 to 4 times higher in the "better" caps he put in. Turns out he had a ground loop issue in his audio gear, and thought the transmitter was humming. The voltages in the transmitter were all about 20% too high (except for the plate), and the idea of even adding series resistance (a bandaid for a bad approach, IMHO) didn't occur to him. Indeed, as it was the transmitter was all out of whack due to the differences in voltages coming out of the PS. He even removed a series resistor added to a diode that replaced a selenium on the bias supply because it wasn't on his schematic.

So I replaced all the capacitors back to the original values (and put back the series resistor in the bias) and everything worked fine. Now this was the case in this specific transmitter, and I know it is not as critical with others. However, I have never understood why values that work in the first place, particularly in choke input PS's with good regulation, are changed to a higher value.

But I'm off topic. Suffice it to say, I do prefer tubulars and find them to work well for bypass & coupling applications. I do tend to use either Polypropylene or even Teflon in some cases though. For circuits requiring stability, I do tend to be more particular and go with ceramics of the higher precision, better tolerance types (C0G or NPO). Z5U and 2E6 ceramic types I avoid completely, due to microphonics issues, particularly in audio stages especially modulators. I discovered in my B&W 5100B what I thought was feedback from my modulation transformer was actually microphonics in the modulator from a few Z5U type ceramics for coupling that found their way in there at some point. For HF or VHF tuned circuits I generally use any good quality silver mica.

Measuring the value of given capacitor to be used, using a heating and cooling method during testing as well, is also highly recommended.

John