As the title states. I need to know the voltge rating of this cap. Thanks!



I understand the Z5U as the temp coefficient, the .05 value, 20% the tollerance but what is the voltage rating!

Dave

No voltage marking usually means 500VDC.


BTW you should not use any X7R or Z5U capacitor to couple signals, they vary way too much in capacitance versus time, temperature and versus applied voltage.

A Z5U can rise to 300% of its marked value when run at 10% rated voltage.

They're also a bit microphonic. And have poor high-frequency characteristics.

They're just barely capable of acting like bypass capacitors, in non-critical circuits.

Agreed, although I always had good results with Erie Z5U's. I like them better than a lot of others, but they're hard to find now.

Larry

Thank you guys. Looks as though I will be discsrding these caps.

Dave

Please don't. I will take them. How many do you have, and what do you want for them? I just bought four hundred 0.01uF discs, and I could use extra 0.05uF caps for my stock. (PM has been sent.)

Hammarlund used ceramic discs for RF bypassing and for RF and AF coupling. I've never seen anyone replace the disc caps with mylars in a HQ-170 or HQ-180 for the alleged shortcomings mentioned above. And I'd bet for the values needed for AF coupling they were either Z5U and X7R dielectrics. Ceramic caps are exellent RF bypass applications. They have much lower internal inductive reactances compared to a wax or mylar cap and are very effective RF bypasses over a wide range of frequencies.

Capacitance change with temperature is easily compensated for by selecting a value that has enough reactance. The engineers who designed those radios knew the limitations of the components they were using and designed around them. I've never been able to duplicate "microphonics" in bench tests. Maybe for audiophile grade gear it might be an issue, but I've seen it in communications type equipment. The only noticeably microphonic discs I've seen were either physically damaged or defective.

But like I said, I'd be interested in any ceramic caps like Dave's that are headed for the dumpster. I'd like to hear from anyone who thought it was necessary to replace the disc ceramics in a Hammurland or other similar communications receiver with a more "modern" device.

Pete

They are yours Pete. PM sent.
Dave

Ceramic caps all look alike on the outside, but they're very different on the inside.

So don't throw out all your ceramic caps. The C0G and NP0 types are very good capacitors, stable and all that. Problem is, the X5U and X7R types look just like the good ones, but have very different insides and much, much poorer and drify characteristics. There's a reason they're required to be clearly labelled with those three letters. They're not all interchangeable. You can use the Xxx caps for bypassing, no problem, as long as the circuit is still bypassed enough at all temps and voltages. And the radio isn't mounted on a jackhammer (microphonics).

An excellent/informative discussion. I never could figure out what those codes meant. Looked in my Mouser (paper) catalog and found most of the code references for operating temperature specifications. Could not find specifications for the following codes: R3L; SL; X5F; Z5P. Anyone have information on those codes, or a site that has complete code references?
BTW-LARRY- I have lots of Erie brand caps.
BOB

MANY thanks, Bob, maybe we can hook up, will send PM....

Larry

Microphonics and C change is mostly derived from audiophool myths.

I challenge anyone to find a 500V .05 disc doing anything of the sort when correctly used.

First of all it is heat that changes the value and that is 99% external for audio coupling and manufacturers have been using those style caps for decades with no ill effects, often during different runs of the same model set and going from paper to disc. Voltage without series resistance does nothing for heat generation and at the impedances involved there is virtually no current flowing either in a Class A amp.

OTOH I would not use a 500V coupling cap of any kind in a tube circuit with more than about 150-200VDC on one end due to spikes riding on the audio signal. This is one of the very few places using a 630V axial lead film or a 1000V disc (which is generally the next higher value altho 600V does exist) makes sense. The factory 500V disc caps in all my sets runing the lower voltages have been fine since built starting in the early 50's.

Do what you want with those caps but IMO they should just be used as suggested.

Pete, Im low on .05's but I can send plenty of .02/600V well made in Japan.

Carl

Sigh. These are not audiphool ravings. They're the industry standard specs for disk ceramics, in force for over 40 years.

The C0G and NP0 ceramics are very good capacitors, low dissipation factor and low drift. They're so good they can be used as resonating capacitors in TV and radio front ends.

The X and Z prefixed caps are A COMPLETELY DIFFERENT ANIMAL. They look the same on the outside, but the dielectric ceramic is completely different-- it's a much higher dielectric constant material, so you can pack in almost 10 times the capacitance in the same size disk, compared to C0G and NP0. This compactness comes at a high price, the dielectric constant varies WILDLY with time, temperature and voltage, adding up to 30% or more. And they have LOUSY dissipation factor, like 5% typical brand new from the factory. And the capacitance goes on a downward slide from day 1, about 6% change per year. Don't believe me, go read the specs:

http://www.ece.ucdavis.edu/vcl/asap/asa ... /X5R_D.pdf

http://www.skywellnet.com/BME%20Hi-MLCC.pdf


Fortunately most bypass applications are non-critical as to exact capacitor value, so there's no problem with having a dozen X5R bypass caps sprinkled around the chassis of your radio. The problem comes in believing that because there are so many of those, it's also a good idea to use them in more critical locations. Not quite so. You shouldnt use them in any tuned circuit or tone control, or audio coupling application. Not unless you can tolerate their ditzy behavior.

Sigh again. Couplates used ceramic discs for audio coupling. Bare ceramic discs attached to the substrate.

Hammarlund receivers used ceramic discs throughout, including audio coupling. I've never encountered microphonics in any set that used ceramic discs for audio coupling, unless the disc was defective. HQ-150 receiver: 0.02 disc ceramic (C40) right off the detector to the first audio. Audio coupling through an off the shelf Couplate to the last audio. I guarantee those weren't C0G or NP0 caps. In seventy years, I have yet to see a restorer raise an issue or identify a problem with Hammurland's use of those devices for audio interstage coupling. Moving ahead, the exact same components being used in the HQ-145. I could keep pulling manuals, but I suspect if these were a problem, Hammarlund would have gotten the hint around the first few production runs. In a high Z circuit (class A grid input, as others noted) small changes in capacitance have less effect than might be expected. The value for the coupling cap is chosen to have a very low impedance over the intended frequency range. When looking into a 1 megohm grid impedance, small variations in the coupling cap's value become insignificant.

They wouldn't be my first choice, but apparently they were used for that purpose in the electronics industry. THD in most AM receivers is mostly limited by tradeoffs for the AGC filter time constants or limitations in the detector than any distortion that might be introduced due to type of capacitor used for the audio stages.

Ref: http://www.classeradio.com/detector.pdf

Pete

Dave,

Back to your original question about the voltage rating:

It would help if you could supply some dimensions for the cap. And, is there anything stamped on the back?

This value, in the Z5U tempco, was used for power supply bypassing in low voltage solid state circuits. Some manufacturers made 6V and even 3V parts. I'm not sure about RMC. The low voltage parts are much smaller than those rated for higher voltages. The leads on the pictured part look kinda small, so perhaps the cap is fairly large; but this is speculation.

RMC was Radio Materials Company, owned by P. R. Mallory, in Indy.

Perhaps you can find a vintage catalog that would list the dimensions for each capacitor. This would help judge the likely voltage rating.

And to join in the fun, I have to say that although the Z5U caps are definitely no good for tuned circuits, they will likely do well enough elsewhere in a small radio. As already stated, you want a COG or NPO part for tuned circuits.

For in-between requirements, an X7R tempco might be a better choice than the Z5U. But I doubt if you could tell the difference in a small radio.

Ted

Ted

Dave was kind enough to offer to send me the caps. I'll be using them for cathode
bypass duty in boatanchor IF and RF stages when they arrive.

Pete

BS, the actual specs have been in place a long time but the audiophools couldnt interpet their own birth certificates


1000% pure BS at least for the disc ceramic item discussed here.

In the real world it is: For instance, a Z5U capacitor will operate from +10 °C to +85 °C with a capacitance change of at most +22% to −56%. An X7R capacitor will operate from −55 °C to +125 °C with a capacitance change of at most ±15%.
In the real world under a tube radio the temperature comes no where close to the limit above and the small change has no effect on the audio in a bandwith restricted radio




Please stop annoying us with more stupid links of caps not even remotely related to this discussion. SMD of all things; your running 1000% on the BS meter so far.

Voltage doesnt even enter the specs and neither does C change over time with the discs. So please stop the ridiculous posts with total misinformation not related to the subject.

Better stay away from Audiokarma as your truly ditzy sources.

Carl

I'm sorry I wrote 300%, I meant 30%, which is fully documented in the documents I pointed to.

It matters not a single tiny whit that it refers to SMD parts, the spec has to do with the ceramics, not the shape.

And I repeat, the X and Z caps are ( and you glossed over this part ), definitely all have a HIGH DISSIPATION FACTOR that cannot be ignored, its easily 5%.

So to repeat: use whatever caps you like, but it's helpful to note that caps that look alike MAY NOT BE VERY SIMILAR IN SPECS. The C0G and NP0's are very good capacitors. The identical looking X and Z's look the same, bypass almost as well, in fact a little better if you consider the benefits of low-Q bypassing networks, BUT THEY ARE NOT SO SWELL FOR HANDLING SIGNALS. A capacitor that varies 10% in capacitance versus voltage is NOT going to be a great choice for putting in a LC circuit, or any kind of tone control. If you look in well-designed stuff, like HP test equipment, pre 1980, you will see PLENTY of X and Z caps, but they're limited to being used as bypasses. When the signal has to actually go through a capacitor, they switch to better quality caps.

I don't get this from any audiphool rag and I agree that a whole lot of the golden-ear writings are way over the top.

It most certainly does as the SMD parts are cramming a lot more C into a small package. You wont even see a Z5U in a low value disc anymore in production.



I didnt gloss over anything, just chose to ignore it as another defective comment. You spend far too much time reading SMD and other dense packaging specs. That .05 DF is at most 1.5% and maybe less as that is in the older and larger size.



You seem to be in a rut and keep repeating that myth while you keep changing the wording. While I would never use a Z5U at the plate of an audio amp as a tone cap Ive no problem using it in the prior stage or in the grid circuit as long as its sized properly such as a 500-600V part. It takes experience plus reading more than current SS apps spec sheets along with audiophool sites to be able to make proper substitutes. And as mentioned on ARF several times many manufacturers went from paper to mylar to disc in the same model during production life and as costs for ceramic went way down. So quit annoying us with the constant drivel.



Meaningless noise again as no signal level is provided nor is there any proof presented that any tube radio is affected at the low levels driving into the audio amp.
There is also a considerable body of proof of over 50 years that shows the typical 1000 to 4700pf Z5U plate blocking disc ceramic cap used in 1000-1500W ham amps has any detuning effect....and again when sized properly. You dont use a 3KV cap with a 2700V B+.

Carl

Thanks all for making this a very informative thread!

Yes, but which versions? Probably not the type in the photo at the start of this thread. That seems to be all that some people are trying to get across.

Sorry, but you're wron, wrong, and wrong again.

The specs for a letter-digit-letter capacitor are an industry standard, and do not vary between capacitors that a the size of quarters or the size of pinheads. The three letters directly and unambiguously map to temperature coefficients, size has nothing to do withit. I llinked to the specs for SMD caps, but they're identical for old-style caps.

See: http://en.wikipedia.org/wiki/EIA_Class_2_dielectric

You're still missing the point when using as an example the plate coupling capacitor out of a power amplifier tube. There a lousy cap is not a problem, as the cap is chosen to have very low impedance at the frequency of interest. That way it doesn't matter if it drifts 30%, it's large oversized value swamps out any variations. Also being large, it has very little voltage drop across it, so voltage changes don't apply. Also it's feeding a tuned circuit which is going to suppress any harmonics caused by the capacitor acting like a varactor. That is a totally different application than in a circuit where the voltage across the capacitor and the charge stored and returned is critical, such as in a tone control, or in a LC tuned circuit.

And there's no point in lowballing the cap change at 1.5%, the manufacturers curves admit that it's 4 to 6%.

And they're definitely microphonic, I used to change them out of RCA movie projector amplifiers -- in one production run they used 0.47 pretty red disk caps which small, modern, and a microphonic disaster.

For more info You might also look over Bob Pease's book "Troubleshooting Analog Circuits", ISBN 978-0750694995, he has several pages on the little-appreciated quirks of ordinary capacitors.

Have you ever seen a .02 ufd disc ceramic cap with a +80, -20% tolerance
that was anything other than a Z5U or similar crap dielectric used for high value capacitance
ceramics? There are about 20 such devices in a HQ-145, including a coupling cap in an early
audio stage.

Personally, I've never seen very many high stability ceramic caps made in values much over 700
pF.

I'll post a photo of the underside of a HQ-150 for those who need the visuals.

http://i271.photobucket.com/albums/jj12 ... CF1578.jpg

Carl pretty much covered all of the bases regarding this subject in his last post,
and nothing in the HQ-150 goes against what he stated in that post. Quote:

While I would never use a Z5U at the plate of an audio amp as a tone cap Ive no problem using it in the prior stage or in the grid circuit as long as its sized properly such as a 500-600V part. It takes experience plus reading more than current SS apps spec sheets along with audiophool sites to be able to make proper substitutes.

Pete

edited model number to HQ-150