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Old 21st December 2011, 01:11 PM   #1
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Default Power supply capacitor question for tubelab simple ss

Just a few questions I had before I go around blowing up caps.

I was wondering if this would be safe to substitute the cornell dubilier caps in the power supply of a tubelab simple se with similar nichicons.

The reason I'm asking is because the cde caps are lower esr. the nichicon caps don't even have esr listed on the datasheet (unless I'm missing it or it's written differently)

Capacitors in question
cap specified
http://www.mouser.com/ProductDetail/380LX470M500J012

cap I was wondering if I could substitute
http://www.mouser.com/ProductDetail/Nichicon/LGN2H121MELB30

according to the datasheets, located here http://www.cde.com/catalogs/380-382.pdf and here http://www.nichicon.co.jp/english/pr.../pdfs/e-gn.pdf
the cde cap rated for about 1.1amps max ripple @ 120hz and the nichicon is rated at .6 amps ripple current.

more details about my planned amp
power transformer (ordered) is the edcor xpwr059 750V (375-0-375) at 175mA (side question, can I expect a B+ voltage of about 375*sqrt(2) if the center tap of the secondary is used as ground with 2 FRED diodes?

output transformers
edcor CXSE25-8-5K (5k primary w/ ul taps, 8ohm secondary)

I will be using diodes instead of a rectifier tube (ordered ISL9R8120P2 FRED)
and a 5H 200ma choke CXC100-5H-200mA resistance 58 ohms
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Old 21st December 2011, 02:20 PM   #2
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The Nichicons would be fine if the larger 30 mm diameter will fit. CDE is rated better but the ripple current will be in the same range as load current (maybe 150 mA) - plenty of margin with either one.

You'll have over 550V at start-up - that's within the typical surge rating but pushing it.
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Old 21st December 2011, 03:16 PM   #3
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would you suggest putting some extra power resistors in series with my diodes? or is there anything else I can do to fix this? I think the choke I'm using has less resistance than other chokes (only 58 ohms) less than the 150 ohm resistor used if the choke is omitted Simple SE schematic

And on another note, I'm a bit confused on the orientation of transformer windings. mainly which wire on the secondary is used for cathode feedback. I attached a picture with my best guess, and the diagram from the edcor site. My logic was that common= ground, but I'm not sure if that's right.

Click the image to open in full size.
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Old 21st December 2011, 04:35 PM   #4
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I haven't caught up on email yet since being on a 3 day road trip with only smartphone internet. I can answer the questions here.

I am away from home on a little vacation, but I have boards with me and I can ship from anywhere. The post office lines are a lot shorter here in a small town in West Virginia than back home in Fort Lauderdale.

Quote:
I was wondering if this would be safe to substitute the cornell dubilier caps in the power supply of a tubelab simple se with similar nichicons.
As many of us have found out 500 volt caps have become rather hard to find. It seems that Panasonic has ceased production, the CDE's have gone extinct and are rather scarce, and what's available is expensive. I bought some of the Nichicons from Mouser and have put them in a board. The board works good, but I have only ran it for a few hours so far. The Nichicons are rated to operate at 105 degrees C where tthe CDE's are only good to 85C. This is why the Nichicons have a lower ripple current rating. I do not expect any problems and I will be using them in a SSE parts kit if they pass my torture tests. I run the amp in all sorts of extreme conditions to make sure the parts aren't going to die at a young age, including running the amp in a closed wooden box (very hot) while playing my guitar through it.

Quote:
side question, can I expect a B+ voltage of about 375*sqrt(2) if the center tap of the secondary is used as ground with 2 FRED diodes
You will only get 1.4 times the secondary voltage with no load or a very light load. I have not tried the Edcor power transformer but I would expect its unloaded secondary voltage to be near 400 volts. This means you will be near 550 volts at power on before the tubes warm up. Most tube amp supplies deliver 1.2 to 1.3 times the secondary voltage with silicon diodes since the diodes only conduct for a small fraction of the time. I see between 450 and 480 volts of B+ in an SSE using the 375-0-375 volt Allied or Hammond power transformer. The actual voltage depends on your line voltage, how distorted your power line voltage is, and the bias current.

At this voltage you will need to reduce the bias current by raising the value of the cathode resistors on the output tubes. Most EL34's or 6L6GC's will glow red under these conditions, but the Electro Harmonix 6550's or KT88's seem to be OK with the 560 ohm resistor. That's what's in my amp.

Quote:
would you suggest putting some extra power resistors in series with my diodes?
I have built amps without the resistors and seen no issue, but this forces rather high peak currents to flow through the diodes for a small fraction of the line current cycle. These sharp current pulses can make the power transformer buzz and can couple hum into the amp through the power transformer. Adding resistance will help reduce the peak currents. You can use a single resistor in the transformer center tap instead of two resistors.

Quote:
I'm a bit confused on the orientation of transformer windings.
There is no standard polarity for transformers. Unless the manufacturer puts the dot next to the wire on the connection diagram the user has no way of knowing which way the trransformer was wound.

I have an amp built with older Edcor CXSE transformers. Mine have blue and black secondary wires. Unless someone post an answer that has used the same transformers you have, the only way to know for sure is to try it both ways. The correct connection will be thee one that gives a lower volume with the CFB turned on. If the amp gets louder or oscillates wheen the CFB is turned on, reverse the wires.
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Old 21st December 2011, 05:52 PM   #5
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by tubelab.com View Post
...
As many of us have found out 500 volt caps have become rather hard to find.....
Weber has 600V and 500V and in sizes reasonable for audio tube amps. Who knows where they get them but it looks like Weber is having them custom built as they come with the "Weber" brand name on them.

Example price: 40uF, 600V, 105C $2.75

I have no idea how long they last or much else about them other then they seem to work and 600V at 105C for $2.75 seems like a deal.
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Old 21st December 2011, 06:52 PM   #6
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I hhave used Weber speakers in guitar amps yeaars ago when Ted waas running the company. They rock!

The can caps look like the same caps sold by JJ, but I have no idea who makes them. The other caps are axial lead which will not fit in a Tubelab board but might be good for a point to point build. I have never tried them though.
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Old 22nd December 2011, 08:36 AM   #7
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Quote:
Originally Posted by tubelab.com View Post
As many of us have found out 500 volt caps have become rather hard to find. It seems that Panasonic has ceased production, the CDE's have gone extinct and are rather scarce, and what's available is expensive.
F&T still produce a nice line of 550/600 Volt electrolytics, both axial leads and can-type (screw-mount). I have not seen radial ones, though.
I get mine from AskJanFirst (no affiliation) and so far they have not let me down (reliability and sound-wise).
I guess, this might be mainly an option for the European forum-members.
But I thought it might be of general interest since these caps are quite reasonable in price and good performers.

Cheers,
Martin
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Old 22nd December 2011, 04:30 PM   #8
kevinkr is offline kevinkr  United States
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FT caps are sold by a number of vendors here in North America as well, (Antique Electronic Supply last time I checked was one) and AskJanFirst also ships to the USA.
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Old 22nd December 2011, 05:23 PM   #9
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Quote:
AskJanFirst also ships to the USA.
That's where I got my D3A's.
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Old 23rd December 2011, 03:55 AM   #10
ke4mcl is offline ke4mcl  United States
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im using F&T 500v lytics in a pair of magnavox console amps. i restored the console and use it at least once a week for hours. no issues yet and its been over 3 years. i got the caps from tube depot.
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