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Old 19th November 2007, 03:42 PM   #41
SY is offline SY  United States
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See my post #21 above.
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Old 19th November 2007, 04:44 PM   #42
Calvin is offline Calvin  Germany
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Hi,

I used simple black school pen ink. It seems to me though that the kind of ink was of lower importance than the kind of glue!
With Tesa clear liquid glue (all purpose, waterbased) it worked very well, with the competing brands like UHU (looks the same, smells the same, tastes the same, costs the same) it didnīt work at all.
The resistivity could be changed with the amount of doping. But I regularly used only 1 to 2 tiny drops of ink with ~100mL of diluted(!) glue (it looked just slightly greyish). You can too reduce the resistivity by a second coating or by spraying (ie thicknes of the coating).
I like that this coating is really totally transparent.

jauu
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Old 19th November 2007, 05:17 PM   #43
gvy is offline gvy  Belgium
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Thanks for sharing Calvin.

I had identical experience over the years with the VELPON school glue + airbrush ink.
I have been always very happy with it. (no problems in many years of use with different ESL's)

The strange thing is that from the 4 hybrides that I have made about 1 year ago for my home theater (my most recent builds) , one did completely fail (no output at all).
yesterday I openend it and measured some things, finally cleaned the membrane with ammaonia and recoated it and it is OK now.
So for the first time I have had a coating problem.
And also a second one has about 4dB less output. So that one I want to redo also.

That is the reason that after all these years of ESL building I want to reconsider the coating issue.

Maybe they ve changed the formula of the VELPON????

geert
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Old 19th November 2007, 08:37 PM   #44
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Geert!

Are you sure it's the coating?

Isn't it dirt collected over time? A common failure of esls.

Is there a contact failure? (could be measured)

Maybe you should measure the resistance of the old coating keeping in mind that dirt forms an insulating part which can be overcome by using a wetted coin (e.g. soap solution) to improve contact. This may leave some stains on your mylar.
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Old 19th November 2007, 09:29 PM   #45
gvy is offline gvy  Belgium
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Quote:
Originally posted by MJ Dijkstra
Geert!

Are you sure it's the coating?

Isn't it dirt collected over time? A common failure of esls.

Is there a contact failure? (could be measured)

Maybe you should measure the resistance of the old coating keeping in mind that dirt forms an insulating part which can be overcome by using a wetted coin (e.g. soap solution) to improve contact. This may leave some stains on your mylar.

Hi Martin Jan,

Those ESL's were only 1 year old .
The ones in my living room are much older and a friend of mine has a set I've made 6 or 7 years ago and they still play well.
All are coated with VELPON school glue with some drops of airbrush paint.

I too find it strange that one of my most recent did completely stop playing.
I have checked the high tension connection and that looked still OK.
I always make a copper tape ring around the complete membrane and solder theHT wire to it .
I measured the membrane surface resistance with the megger at 2500V and it became very high.?????
So I simply cleaned of everything very thorougly and recoated the membrane and now it plays OK.
I did some measurements yesterday and the efficiency is the same as my others now.

That is the reason I am going to try some new experiments with coating.

There could have been 1 reason.....
I do use a small electrical heating in my home theater (in my basement) and that did have it's place near this particular ESL....
Maybe the coating dried out completely?
Strange that it didn't recover after I replaced it , if that was te reason.



greets
Geert
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Old 20th November 2007, 07:31 PM   #46
Nevod is offline Nevod  Russian Federation
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gvy
I'm afraid that VELPON glue is not sold in Russia. Though, some comparable glue can surely be sold, but it won't be easy to find it. What's VELPON composed of?

One guy has tried to use doped Nylon coating, adding some NaOH into nylon to reduce resistance, and dissolving it in vinegar essence acid. The coating proved itself not to be stable, af it fell off in several months. He also applied coating inbetween two layers of mylar, and it fell off as well. Though, glue is ought to be more stable.

In double-layered coating, the top layer of nylon or teflon is actually only used for protection, and does not create too high a resistance. Using carbon black instaed of graphite was proposed, but it's hard to find a consistent source of carbon black.

Teflon is used in commercial ESL, so it can be somehow made to stick to mylar Maybe, coronary prepared mylar is coated with dissolved hot teflon. There are several kinds of teflon, they all have almost the same properties, but different temperatures of melting. And, afaik, it is possible to dissolve teflon in some reagents on temperatures well below melting point. Besides, it is used in electrets.
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Old 20th November 2007, 08:24 PM   #47
Calvin is offline Calvin  Germany
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Hi,

which ESL usesTeflon in any form? And for what purposes?

jauu
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Old 20th November 2007, 10:35 PM   #48
al2002 is offline al2002  India
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I was told that the membrane of the tweeter section of the Cadence ES hybrid is made of Teflon. Have not take one apart to verify this, though.

Quote:
Originally posted by Calvin
Hi,

which ESL usesTeflon in any form? And for what purposes?

jauu
Calvin
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Old 21st November 2007, 01:18 AM   #49
Nevod is offline Nevod  Russian Federation
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Calvin
Sound Lab states that they use Teflon coating.
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Old 23rd November 2007, 02:38 PM   #50
daanve is offline daanve  Netherlands
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Are you referring to this information ?

" Also, a new micro-thin teflon-based coating on the membrane eliminates fatigue due to continual high-level signals with the resulting large membrane excursions. These technical updates provide a significant improvement in both performance and reliability, which is crucial in meeting the greater demands of higher listening levels. "

This is more to do with the mechanical/structural aspects of the membrane.

micro-thin teflon coating
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