physical size of power supply filter capacitors matter?

[mikepukmel]

I found these Nichicon 18uf 500v polarized electrolytic capacitors, cheap, a little over 2 bucks.

They are radial so won't be a snap in replacement for old amps.

The data sheet says "suited for ballast application".

They are about 1/4 the physical volume of similar rated 16uf 475v or 22uf 500v F&T.

I haven't been able to get comparable data sheets for both capacitors.

Are the smaller capacitors usable for guitar amp power supplies?

Which ratings should I look at when comparing capacitors?

Thanks
Mike

[Justin Thomas]

My first question would be, "what's the temperature specification on those caps?" Generally for guitar amps it's either 85°C or 105°C. Should be on the data sheet somewhere.
It's not much of a secret that Sprague Atoms are WAY oversized, and F&T (which I like and use) are better in that regard, but I'm sure they're still a lot bigger than they would absolutely HAVE to be. There's a certain amount of "show" that goes into manufacture of parts specifically marketed to guitar and amp builders, and cosmetic considerations for vintage restorations. Wouldn't look as good to have a bunch of thimble-sized caps in the doghouse of that Super Reverb...

Justin

[Tom Phillips]

The physical size doesn't matter as long as the relevant specifications are suitable for your application. The full set of specifications is vastly more extensive than the information that is not made available by the various musical instrument specialty parts suppliers. You said "The data sheet says "suited for ballast application." Can you post a copy of that data sheet so we can see the other information listed? If you will tell us the model number of the Nichicon caps you are looking at then we should be able to locate a copy of the full Nichicon data sheet.

Attached is an example of a data sheet for the UPW line of Nichicon capacitors. With this type of information one can evaluate the actual differences between the various capacitor models which, when the seller only lists the capacitance and the voltage rating, would otherwise appear to be identical. A similar data sheet will be available for the Nichicon cap line that you are interested in using. Can you find the actual Nichicon part number?

Nichicon UPW Cap Data Sheet.pdf

Edit: When you buy one of the house branded caps you usually can't determine exactly what you are getting. Furthermore, there is no guarantee that the seemingly identical part that you buy one day is the same as the one you bought last year. The seller may not even know if their supplier made changes. That's why we often rely on field reports from other users to evaluate the overall quality of a given brand.

[mikepukmel]

sure, thanks. The data sheet (at least what Mouser has)

https://www.mouser.com/datasheet/2/2...cy-1219498.pdf

The data sheet says 105C

https://www.mouser.com/ProductDetail/647-UCY2H180MHD

[Tom Phillips]

sure, thanks. The data sheet (at least what Mouser has)
https://www.mouser.com/datasheet/2/2...cy-1219498.pdf
The data sheet says 105C
https://www.mouser.com/ProductDetail/647-UCY2H180MHD

In addition the data sheet states "High ripple current and Long Life product withstanding load life of 10,000 to 12,000 hours at +105°C." Seems like a good quality component.

Note that the load life is specified at full voltage and max rated temperature. At lower temp and voltage the useful load life significantly increases. Lower end parts have load life ratings, when you can even find the spec, of as little as 1,000 hours.

[mikepukmel]

Thanks Tom. I haven't found 105c rated caps on the amp parts sites. The F&T's are most all 85 and have to dig for that as well. One of my friends from high school, who has done electronics work for a long time, said the 105c caps will be more stable, even though you won't ever run them that hot.

***

Wow, 1000 hours, thats only a couple or 3 years of practice time!

[Tqi]

Wow, 1000 hours, thats only a couple or 3 years of practice time!

To put it in perspective, that's the same estimated lifespan as the standard 63PS Soviet Output Pentode (Side note, the 6P3S-E military-grade version is 5000 hours). Imagine if you had to replace your entire set of electrolytics every time you changed output tubes!