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Old 3rd April 2012, 08:24 PM   #1
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Default Which 40 mfd 450v caps to choose

I need to replace the original 3 section power caps in a pair of Fisher 30A mono amps. They are 40/40/40mfd. 450 v. I can get suitable can caps from Antique Electronic Supply supposedly made on the original Mallory equipment that will go right in. Is this the best sounding choice? would I be better off with 3 seperate caps like the Sprague atoms? I heard they were good. Don't know if the newly manufactured 3 section cans will be as good or better than the originals. Cost is not a concern, just want the best sound possible. These are amazing amps and I don't want to screw them up. Anyone out there have experience with these new electrolytic cans? Alot of tech's won't fool with them and like to use seperate caps mounted inside the chassis instead of on top. Is this for convenience? cost? or sonic reasons? Any thoughts on this subject would be greatfully appreciated, thanks.
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Old 3rd April 2012, 10:04 PM   #2
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Cost and life spec. I've used the cans from FP (supplier to tubesandmore.com and triodeelectronics.com) and they work fine in my H182 organ. The old ones are a ***** to get out, I have to use a 130 W iron to soak the solder off and usually end up tearing the tabs off the old can. Furthermore, if FP has a spec for life or any test data, I haven't seen it. I replaced the can cap in my ST70 in 1972 because the power was 7 w/ch with the original dynakit can cap. Since a new can installed by the dealer was $50, and I paid $60 for the amp, I installed then four axial sprague atomlytics tied together in a bundle, which got me to 17 VAC into 8 ohms. The power was back down in 1980. A new from Stereo Cost cutters CDE can cap went in about 1982, was only used about 4 hours because I couldn't buy new output tubes. Got the new output tubes from JJ in 2011, enjoyed 35 W/ch one night and the next night the CDE can cap blew the fuse and leaked. I've installed Panasonic and Nichicon radial lead caps under the deck, 39 uf and 22 uf instead of 40 and 20. 450 V instead of 520V the dynakit had originally, no problems yet after 6 months. You can buy Panasonic, Nichicon and Rubicon caps in 3000 to 10000 hour predicted life grade, whereas Vishay Sprague caps (still made in USA) have no life rating that I can find. I presume they are about the same as the old atomlytic which was a quality cap but had nothing special as a sealant. The organ is still running fine on the FP caps I put in it in 2009, but it doesn't get the hours of use the hifi does. I use terminal strips from T&M or triode to install the radial lead caps under the deck, and buy new 600v wire from t&M as required. I put steel mesh in the old can holes, tying it in with twists of steel wire.
As long as there is enough capacitance, I don't hear differences between FP cans and Panasonic or Nichicon radial caps. There was a huge difference in sound on the organ when I replaced the old dried up 1968 caps, nearly every cap, some cans, some radial or axial. I put a few 1000 hour multicomp (newark) or CDE caps in the first H182 organ, I won't be buying that grade again. I did a sound check after nearly every cap installed, since I make a few bad joints occasionally, barring those problems nearly every cap installed improved sound quality or function. 71 e-caps went into the H182, and I have 4 more organs to do. Just finishing putting all new e-caps in a Hammond A100 that had such low hours the screws that allow you to oil it still had all the lead hole expanders (which means it had never been oiled.)
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Last edited by indianajo; 3rd April 2012 at 10:13 PM.
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Old 6th April 2012, 01:43 PM   #3
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Thanks Indianajoe for your insight. Sorry to be so dumb, but I didn't realize I could get life specs on the caps. Perhaps that is where I should focus to make my choice. Those must be some fine caps from the orig. Fisher factory since they can last 50 or so years. I have a few pairs of these amps all running on the original filter caps. Can't imagine putting up with something that only lasts a number of years. Very doubtful that the new versions will hold up like the originals. Any advice on what brands are available with long life specs in addition to Rubicon, Nichicon, Panasonic? Panasonic has often been mentioned as good quality and you say they are available in 10,000 hour, is that right? Is 10,000 about as good as it gets? Thanks again for being the only one to respond so far, Chris
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Old 6th April 2012, 07:00 PM   #4
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If you look at newark.com click passive components, click capacitors, click aluminum electrolytic, you'll find that the cap table has hours life shown. I don't know any other vendor that shows these numbers, they make you download the datasheet and read it.
Don't put a minimum on hours life the temperature grade mixes them up. 105 deg C caps might last longer but 85 is adaquate for tube equipment. Check your dropping resistors before ordering, they are often heat damaged and over value. Don't buy under 400v rated dropping resistors. (this forces you to 2 or 3 watts usually). Metal film resistors are the current standard part, not carbon composition.
Newark is in NC, but for delivery to a house make sure to click USPS as the shipping option, and make sure you check stock before you buy. Click "hold and ship all at once" or you may pay 2 or 3 shipping charges for out of stock stuff. I usually put a minimum and maximum capacitance and minimum voltage when I buy e-caps, to get the best bargains. "Stale" newark caps come at a discount, and must be charged up with a battery or DVM to 2v or so before use, (reformed). An ohms check does it. Mouser.com has okay service , is in TX, and has links to cap datasheets, but you have to look up the life numbers on datasheets. T&M and triode don't list the cap life and don't link to the datasheet, although for tubes and 600 V wire and terminal strips they can't be beat.
United Chemicon has a crummier ripple spec at end of life, so I view their life numbers as fudges to look better than the others. They have been made in C**** also. Also CDE. Xicor has been all C********, also. Some vendors like mcmelectronic.com don't even tell you what brand the cap is , or life, or ripple spec, or anything. Theirs are "audio grade" if you like beautiful words that don't mean anything.
If you have a VOM with a 20V AC scale, or a VTVM, check the voltage going into your speakers at full power. {V^2}/R tells you the watts out where R is your speaker ohms ( you can measure that if you don't know, calibrate with aknown resistor as 1-10 ohm measurements are sensitive to the battery state). DVM's lie a lot at these low voltages on the AC scale, and the fluke meter the factory loaned me wasn't any better. VOM, VTVM, or scope to make this measurement. 0.7*Vpp on scope gets Vav for power measurements.
The McIntosh salesman in 1971 caught my 35 W/ch amp putting out 7 W/ch, I doubt if your fisher caps are any better. They didn't have epoxy capacitor sealant in 1960, only rubber. Look at the 1960 tires on your 1960 car for what rubber does. What, no 1960 tires? Well your caps are just as bad, oxygen is everywhere. My organ caps were all working, but it sounded like a kazoo. Every one I put in made it sound better, and 6 of them doubled the volume for every pair I put in. After the caps are in your amp still may need rectifier tube (B+ voltage is low compared to schematic) or output tubes (power is still low with new caps and B+ okay). I bought some JJ output tubes last year from T&M, the ST70 is back to 35 W/ch.(17 VAC at 8 ohms). Beeping music instead of symphonic is better for power measurements, as synthesizer beeps out of a radio are like a test wave out of a generator. Slum a little to find a station with beeps for "music" and turn up the volume.
Before making high voltage measurements (above 25 VDC) read high voltage for newbies at the top of the thread here. Simple rules, deadly voltage if ignorant.
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Last edited by indianajo; 6th April 2012 at 07:13 PM.
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Old 9th April 2012, 01:31 PM   #5
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Wow Indianajo, thanks again for all the good advice and info! I will check out newark asap. Take care, Chris
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Old 9th April 2012, 05:22 PM   #6
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Just general practice and results ATMO - not to be mistaken for hard science ......

They don't make electrolytics the way they used to. They make them better. If the objective is a solid, good-sounding repair, I would happily go with 3 x 47uF / 500V F&T branded axial caps or something like a 47uF @ 450V modern radial from someone like Panasonic or Nichicon (whichever had a better fit) and call the job done. Either way, I want to see a 105C temp rating in tube gear.

You can go with the CE caps, but they have proven a bit less reliable than the major market stuff.
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