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K40y-9 K42 outer foil markings

75.192.236.185
Posted on November 7, 2010 at 14:43:25
Taz


 
I know this has been an area of discussion with several threads discussing this topic in the past. I did searches regarding capacitor orientation of the K40's and here are some results I found:

1. "On the Russian caps,the plus side always goes in the direction of the writing unless the Russian that was building the cap at the time was partying on too much Woodka or Vodka and then you may get whatever."

2. "Orienting the writing of the cap from left to right, the left lead is the internal winding and the right lead is the outer winding. "

scenario 1 - so this means + side will be the right side assuming your holding the cap correctly with the writing going from left to right. (i.e arrow points to positive side)

scenario 2 - so this means the + side will be the left side; *(i.e the arrow points to negative side)

Which is the proper way ? I know many say this is not an issue with non-polarized caps, but if there is a way to determine the outer foil it really does make sense to try and connect it in circuit to minimize noise.
After all we go through all the trouble to properly design good grounding topologies to minimize noise, why not take advantage of this orientiation.

* on the k40's there is an inverted C with an arrow inside that points to the right when viewing the cap with the writing going from left to right.
K42's just have a symbol on them.

 

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RE: K40y-9 K42 outer foil markings, posted on November 7, 2010 at 19:41:25
Neff


 
Using a K40Y-9 on a high gain circuit can induce hum. Use tinned copper wires under a piece of heat shrink & ground the metal case. Any induced hum will be removed.

 

RE: K40y-9 K42 outer foil markings, posted on November 7, 2010 at 21:41:24
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 I find just grounding the case does it also but I agree with you about the better leads.Using some nice copper wires or even stranded silver plated or copper makes a big difference in many areas.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: K40y-9 K42 some confusion about grounding, posted on November 8, 2010 at 06:10:15
Taz


 
I was unaware that using these caps (K40's, K42's) on a high gain circuit could induce hum. My confusion with grounding the case is that I often wrap these caps in clear shrink to keep the case from contacting any other part of the circuit, thus causing a short. This is usually due to the tight spaces working with vintage gear.

How would u couple the ground to the case to ensure good solid contact? Are you suggesting that the shrink will do the trick?

Just want to be clear.

 

RE: K40y-9 K42 Michael are you using them this way?, posted on November 8, 2010 at 06:17:53
Taz


 
Hey Mike.

Are you grounding the case with a wire in your projects? If so, how to you secure the ground to the cap? (i.e. maintain good contact with case) Also, can you clarify on how to locate the outer foil on these caps. From my reading in the forums here, you seem to be an expert on these caps.

I think if you have a correct process on how to locate the outer foil, assuming the Russian guy who made the cap labeled it properly, the hum will go away without grounding the case.

Just a thought. I think if you have to run a drain from the cap case then these caps are not good for low level signal use and an alternative would be a better choice.

 

RE: K40y-9 K42 Michael are you using them this way?, posted on November 8, 2010 at 08:36:05
tubegarden@aol.com
Audiophile

Posts: 540
Joined: June 28, 2007
 Hi Taz,

If you install both caps using whatever orientation method you like, and measure hum, try reversing both caps. If the hum goes away, you are done. If not, you may think you know more than is actually happening ;)

Happy Ears!

Al Marcy

 

RE: K40y-9 K42 some confusion about grounding, posted on November 8, 2010 at 09:10:01
Jim McShane
Dealer

Posts: 5928
Location: Chicago
Joined: January 13, 2003
 Inducing hum is not some specialized property of the K40/K42 caps. I suspect ANY cap you put in the same location that's of the same physical dimensions and lead lengths will do the same thing.

IMHO the orientation of the outer foil makes a small difference - and only in the most sensitive circuits. And then only when the outer foil has a low impedance connection to ground.

It's easy to solder to a K40 case. Take a small file and remove the shiny silvery colored outer plating (and paint if any is present) until you see the copper underneath - it only takes a few file strokes. Remove a small "pad" area, then clean that area with alcohol or a non-residue cleaner of some sort. Using normal electronic solder then solder the wire to the case. It doesn't take a big iron, I can solder just fine with my 35 watt Weller iron. It works great.

Then use some heat shrink as a "strain relief" to hold the wire in place.

It's a one minute task is all!!

 

RE: K40y-9 K42 Michael are you using them this way?, posted on November 8, 2010 at 12:44:49
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Taz
usually what I do is just lay it snug to the chassis.Thats usually all it takes.Its only in rare situations where you have to do that but also,you can wrap wire around the capacitor body and ground it.Also,I have seen regular film and foil caps cause hum in a preamp with the bottom cover removed and yet,I have seen k40s in that same preamp cause no hum with the bottom removed,as long as the caps were grounded at the case.Go figure! I guess it just depends how you set them up.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: K40y-9 K42 some confusion about grounding, posted on November 9, 2010 at 14:42:18
Neff


 
Yes, the heat shrink provides good enough contact. I tin each wire (time consuming) and fan the wire out with for a large contact surface.

 

RE: K40y-9 K42 some confusion about grounding, posted on November 9, 2010 at 14:46:47
Neff


 
I prefer no heat with wire under heatshrink myself.

 

RE: K40y-9 K42 some confusion about grounding, posted on November 9, 2010 at 18:37:28
Jim McShane
Dealer

Posts: 5928
Location: Chicago
Joined: January 13, 2003
 I always prefer a "gas-tight" connection which the solder provides. After "x" years corrosion will almost certainly work its way under the tubing and corrode the wire.

There is so little heat involved in soldering to those cases once the bare copper is exposed that I could hold the cap in my hand while soldering in most cases. As I said, my 35 watt iron was plenty of heat. As well, there is likely more heating going on from normal lead soldering than the ground wire attachment.

 

RE: K40y-9 K42 outer foil markings, posted on November 11, 2010 at 06:18:02
Thermionic27609
Audiophile

Posts: 411
Joined: March 29, 2009
 Taz,

If you have an oscilloscope, it's not that hard to test for the outer foil lead. Hook the ground and scope input across the capacitor on a sensitive setting and wrap your fingers around the cap. Note the scope reading. Then, reverse the leads. See if you get a lower or higher reading on the scope. You should get a lower reading when the outer foil is connected to the scope's ground lead.

Alternatively, if the capacitor has a sufficiently high voltage rating, you can use something like a Fluke VoltAlert--an inexpensive device electricians use to test for hot AC wires. Hook the capacitor across your house AC. Use the tester to find the Hot lead and then scan the body of the capacitor. If Hot is connected to the outer foil, you'll usually get a Hot reading over most of the body of the capacitor. If Neutral is connected to the outer foil, it will shield the Hot wire, and the tester won't show a Hot reading from the capacitor body.

Once you get the hang of it, you can do it very quickly. If you use the AC line method, make sure to discharge the capacitor via a resistor before installing it.

 

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