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Old 16th October 2012, 09:48 PM   #651
Legis is offline Legis  Finland
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Quote:
Originally Posted by bolserst View Post
Thanks for the clarification on the recoating and charge ring.
Your experience is very puzzling/concerning as this is the first I have heard of anybody having issues with Licron coating evaporating after a few months of use. I have one pair of panels that have been in daily use for nearly 3 years with no loss of sensitivity or change in charge rate.

Did you notice any difference in the appearance of the coating?
For instance, did you notice a pattern of rings that match up with the perforations in your stators? This might indicate low level ionization from the sharp edges of the stators was attacking the coating.
The coating looked untouched, nothing had changed compared to when I applied it (at least to my eyes). It had not even collected any dust that is worth to mention, even though I vacuum cleaned the membrane (through the stators) only once during this time. I used 4,6kV bias the whole time and the stats were completely turned off for every night to avoid dust collection.

Has someone else noted that the feel of presence, attack and dynamics change when the surface resistance of the coating changes, even though the sensitivity does not change much? The net effect to the sensitivity was only 1,5-2dB, and I could still play >100dB(C) with music material (Radioshack meter), but the sound was much gentler, politier and lacked the huge drive that is there when the surface resistance of the coating is lower (meaning normal Licron). Sounded a tad like the sound was not projected from the speaker/membrane, but little behind it, if it does make any sense.

Last edited by Legis; 16th October 2012 at 10:05 PM.
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Old 16th October 2012, 10:47 PM   #652
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Quote:
Originally Posted by Legis View Post
The coating looked untouched, nothing had changed compared to when I applied it (at least to my eyes).
I'm stumped.
You don't use particularly high bias voltage or stator voltage.
There was no obvious physical change to the coating.

Is it possible that your assembly method could have physically stressed the coating along the spacer boundaries adjacent to the copper tape? I remember you mentioning cranking down on the bolts that hold the front and rear stators together.
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Old 16th October 2012, 11:54 PM   #653
Legis is offline Legis  Finland
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Quote:
Originally Posted by bolserst View Post
I'm stumped.
You don't use particularly high bias voltage or stator voltage.
There was no obvious physical change to the coating.

Is it possible that your assembly method could have physically stressed the coating along the spacer boundaries adjacent to the copper tape? I remember you mentioning cranking down on the bolts that hold the front and rear stators together.
Yes I have dampened the stators with nylon bolts, but I don't think they affect the membrane. The front stator is mainly clamped towards the rear stator, so the membrane should not be affected much. Maybe there could be a slight difference but I can hardly believe it has caused this gradual effect.

I have wondered if the reason is the slightly porous (not completely transparent) surface that the sponge application method gives? Maybe this affects somehow, combined with the very thin layer to which the sponge application results.
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Old 17th October 2012, 03:34 AM   #654
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I tried to measure the resistance on the adhesive side of the copper foil before, and I got so high resistance that my meter couldn't measure. So, I never thought of putting the adhesive side onto the diaphragm. I wonder if you guys have done the same measurement?

Wachara C.
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Old 17th October 2012, 04:35 AM   #655
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Quote:
Originally Posted by chinsettawong View Post
I tried to measure the resistance on the adhesive side of the copper foil before, and I got so high resistance that my meter couldn't measure. So, I never thought of putting the adhesive side onto the diaphragm. I wonder if you guys have done the same measurement?
Measuring the adhesive side of copper foil with non-conductive adhesive I get > 100 Mohm between probes placed one inch apart.
For copper foil manufactured with conductive adhesive, I get about 10 ohm.
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Old 17th October 2012, 05:00 AM   #656
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Quote:
Originally Posted by Legis View Post
Yes I have dampened the stators with nylon bolts, but I don't think they affect the membrane. The front stator is mainly clamped towards the rear stator, so the membrane should not be affected much.
I was wondering about possible clamping stresses on the left and right side spacers adjacent to the copper tape. The thought was this might slowly cut off the inner area of the diaphragm coating from the outer coating strips on the spacers that contain the copper tape.

Quote:
I have wondered if the reason is the slightly porous (not completely transparent) surface that the sponge application method gives? Maybe this affects somehow, combined with the very thin layer to which the sponge application results.
It's certainly possible, but I haven't experienced anything similar to date.
I will keep my eye out for similar behavior with thinner, sponge applied Licron coatings on some of my test panels.
The reason I had previously asked about any changes in appearance was that I did some destructive testing of Licron coating, subjecting it to hours of heavy corona discharge and ozone. Once I started to notice changes in the physical appearance of the coating in the areas of most vigorous corona I could also measure increase in the resistance. These areas appeared to be thinned and slightly more hazy.
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Old 17th October 2012, 08:28 PM   #657
Bazukaz is offline Bazukaz  Lithuania
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Hi,

So finally I have been able to source a full can of Licron crystal, as the current small sample is running out. I have had to carry it to the plane, so spilled the pressurized can to small bottles.
Anybody knows what is the shelf-life of it after having received contact with air(bacterial attack, etc.) ?

Regards,
Lukas.
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Old 18th October 2012, 02:14 AM   #658
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Quote:
Originally Posted by Bazukaz View Post
Hi,

So finally I have been able to source a full can of Licron crystal, as the current small sample is running out. I have had to carry it to the plane, so spilled the pressurized can to small bottles.
Anybody knows what is the shelf-life of it after having received contact with air(bacterial attack, etc.) ?

Regards,
Lukas.
Told ya! Use water based staff! Check Finland distributor of 6300/6400
Armeka Engineering ESD | Yritys Ask for 4oz bottle.
back to the subj
I believe it would be O'K as long as solvent stays in as in any lacquer/paint. It's alcohol based: go figure.
quote
10. STABILITY AND REACTIVITY
STABILITY: Stable under normal conditions.
POLYMERIZATION: Will not occur.
CONDITIONS TO AVOID: Heat, flames, ignition sources, and incompatables.
HAZARDOUS DECOMPOSITION PRODUCTS: Hazardous decomposition products include oxides of carbon,
silicone, and nitrogen.
INCOMPATIBLE MATERIALS: Oxidizing materials
end quote
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Old 18th October 2012, 11:36 AM   #659
AndreaT is offline AndreaT  Italy
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Hello Bazukaz,

the next time you wanna buy a can of Licron Crystal, I kindly suggest you to buy it in Europe.

You should contact (as I did) the master distributor ITW Contamination Control: www.itw-cc.com

ITW Contamination Control
Saffierlaan 5
2132 VZ Hoofddorp
The Netherlands
Tel. +31 88 1307 400
Fax. +31 88 1307 499
Email: info@itw-cc.com

They will address you to the nearest /proper reseller.

Regards,
Andrea
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Old 19th October 2012, 04:05 AM   #660
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Quote:
Originally Posted by Legis View Post
Has someone else noted that the feel of presence, attack and dynamics change when the surface resistance of the coating changes, even though the sensitivity does not change much? The net effect to the sensitivity was only 1,5-2dB, and I could still play >100dB(C) with music material (Radioshack meter), but the sound was much gentler, politier and lacked the huge drive that is there when the surface resistance of the coating is lower (meaning normal Licron). Sounded a tad like the sound was not projected from the speaker/membrane, but little behind it, if it does make any sense.
After thinking about your description a while, I think I may have experienced something similar once with an Acoustat panel. It seemed to be totally lacking in low end authority and sounded a little more distant. The panel did have slightly less output than others I had on hand, but not enough to make me think that was all there was too it. After more careful measuring with mic positioned close to diaphragm, there were some areas of the diaphragm that weren't producing near the SPL of other areas. The far field result was that for midrange and higher frequencies, the SPL was not that affected although there was some phasiness induced from the multi-source effect. For low frequencies, the areas of the diaphragm not receiving as much driving force were being driven backwards by the areas around them that were receiving full driving force, resulting in diminished bass authority.

After cracking the panel open, I could see damaged areas in the coating that were leading to the problem.
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