Upgrade Caps

[quomaya2]

Do you think that these capacitors would work and sound well in C1-C4 in an St-35?

http://cgi.ebay.com/5-SPRAGUE-400v-0-1uf-BLACK-BEAUTY-Tube-Amp-Capacitors_W0QQitemZ190206134913QQihZ009QQcategoryZ36336QQrdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem

[quomaya2]

Do you think that these would work and sound well also?

http://cgi.ebay.com/5-0-1mF-1000v-PAPER-IN-OIL-SOVIET-K40U-9-CAPACITORS_W0QQitemZ180195720568QQihZ008QQcategoryZ71573QQrdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem

[rhing]

According the the eBay listing for the Sprague Mylar film caps:

These are used out of unused WW2 Military radios. A lot of radios and transmitters built for the war were never even turned on, and were sold to surplus houses still in the sealed box's. Parts that were sold to the Military were always tested to the limit for tolerance.

Funny thing is that Mylar wasn't invented until after WWII. It was invented in the early 1950's. This looks very suspicious.

I can't speak about the PIO caps. They come from overseas, and I am always reluctant to purchasing anything from the old Soviet Union or former Eastern Bloc nation using my credit cards or PayPal. There are too many scammers out there. Just my $0.02.

[dcriner]

The first listing is for used Sprague Black Beauties. They are very often leaky (paper dielectric, not mylar). Leakage often leads to their exploding (splitting). Since these are used, some of their leads may be cut too short? I have encountered many exploded Black Beauties in old radios.

The Russian oil caps remind me of Sprague Vitamin Q caps, at least by appearance. Vitamin Q caps are good.

[quomaya2]

So, only paper dielectric black beauties are leaky, because the ones I found are mylar.

[TerrySmith]

Look at Phil's old radios, http://antiqueradio.org/recap.htm, for a really good tutorial on capacitors.

Old capacitors are highly UNreliable, they tend to short which causes many different things to happen such as that weird pop or sizzle, or at worst thermal meltdown of your expensive output tubes!

Any modern capacitor sounds very good, from the cheapest Xicon gumdrop, to the expensive "botique" brands. I usually buy what phisically fits best.

[TomMcNally]

Here is another link about not using Black Beauties

http://www.tmworld.com/article/CA439412.html

The caps called for in the parts list will work just fine, it's
doubtful there will be any sonic advantage to anything else.

[dcriner]

So, only paper dielectric black beauties are leaky, because the ones I found are mylar.

Perhaps so - but the "mylar" black beauties advertised above (on eBay) were supposedly pulled out of radios built during WW2 - before the advent of mylar.

Leakage can be measured with a high-voltage cap checker. You can also use a capacitance meter (even though a high-voltage test is better) - if the cap's value measures high, it is likely because of leakage. Lastly, you can use a digital ohmmeter - the resistance should read infinite.

I recommend that any NOS caps be tested for leakage before installing them in an amp.

[K-MAN]

The old mylar Sprague cap's are popular with people making guitar amps I believe because they give it a certain type of sound that some rock players love. My friend usually has allot of Black Beauties left over when he recaps radios and he sells them on ebay for a good price because of the big demand for them.

[EWBrown]

Most of the five or six decades old caps of that series (black beauty, bumblee bee, black cat, etc) were never designed to last 50 years, and most are gone bad even just from sitting around for so long.

FWIW, most WWII vintage radio restorations include replacing ALL of the caps except for variable and tuning caps. Even the old carbon comp resistors have usually drifted well out of spec as well.

Capacitors and beer don't "age" very well Yellow_Light_Colorz_PDT_02 Yellow_Light_Colorz_PDT_04

I've used the Russian K40y series PIO caps, with excellent results, though I purchase them from either "kwtubes" or "sovcomm" as these both are good sellers with excellent reputations and service. I don't know about "silver silk", so I can't comment pro or con. The ST35 doesn't need the 1KV rating, the 400V caps are more than good enough and easier to fit on the PC boards. These are closely equivalent to the vintage Sprague "Vitamin Q" capacitors of long ago.

My other favorite "eastern bloc" seller "anthonywest" seems to have disappeared from e-bay.

/ed B in NH

[DerekVa]

Capacitors and beer don't "age" very well Yellow_Light_Colorz_PDT_02 Yellow_Light_Colorz_PDT_04

I've used the Russian K40y series PIO caps, with excellent results, though I purchase them from either "kwtubes" or "sovcomm" as these both are good sellers with excellent reputations and service. I don't know about "silver silk", so I can't comment pro or con. The ST35 doesn't need the 1KV rating, the 400V caps are more than good enough and easier to fit on the PC boards. These are closely equivalent to the vintage Sprague "Vitamin Q" capacitors of long ago.

/ed B in NH

Ed - is it safe to say that the Vitamin Q Sprague caps are an exception to the 'capacitors don't age very well' maxim? Most of the ones I've used (provided they don't leak) have worked well.

-D

[EWBrown]

THe PIO caps like Vitamin Qs seem to last forever. The old lower cost dry paper caps don't age well, and tend to deteriorate over time, and using any of them that are 40-50-60 years old is inadvisable. They may measure as "good" but can quickly break down under normal voltage operating conditions.

The K40y9B (K40U9V) PIOs are very mich like the Sprague VitQs, and the green K75 Russian PIOs are Polyprop In Oil, and are still quite good.
VitQs can be pricey, the K40Us are fairly inexpensive from any of the "easteru bloc" vendors.

I posted more info about these a couple years ago under the term "Kommie Kaps" (which is a term I borrowed from some folks over at Bottlehead).

Decrypting Those Mysterious Russian Capacitors:

http://diytube.com/phpBB2/viewtopic.php ... highlight=

/ed B