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Old 13th March 2013, 03:30 PM   #61
Bazukaz is offline Bazukaz  Lithuania
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Hi,

Quote:
Originally Posted by portreathbeach View Post
So basically I should get the parts together to build the power supply and also the step-up transformers for the stators and experiment with panels? Sounds fair.
Exactly. You need to gain some experience before building a final set.

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Originally Posted by portreathbeach View Post
Is the schematic that Jazzman uses a good one to use? It seems simple enough to build and I'd rather use this type of circuit than a switch mode type.
It is good. While it does not provide precision tuning of bias supply voltage The schematic is simple to build and reliable. No possible interferences from switch mode operation. There is a set of definite output voltages after each multiplier stage; any of these can be used.

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Originally Posted by portreathbeach View Post
Another quick question. I can get the mylar from eBay no problem, but wanted to know what the best coating to use on it is. There are several different sprays and compounds, like graphite etc. people are using, what is a good coating to start with, nothing too expensive or hard to work with would be preferable.
Please read this thread :

ESL Diaphragm coating

There are a variety of formulations. Currently Licron Crystal is very popular here. Other antistatic coatings may work, also there are companies who sell the coating specifically formulated for ESLs.
Graphite is not the best material to start with. It is very difficult to apply in a layer having sufficiently high and uniform resistance. If you simply rub graphite on the resistance will be far too low causing charge migration and increased distortion. Wiping with alcohol can help but the process becomes long and difficult, and you will need some equipment to measure if resistance is uniform and high enough.
Also there is no possibility to selectively exclude areas of membrane like bolts, neither to remove the layer with solvent and re-apply again.

Lukas.
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Old 13th March 2013, 04:16 PM   #62
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Yes I would start of by building the Bias supply.
This will help you to get accustom to high voltages and use it to test various coatings for breakdown failure.

The biggest mistake I have seen happen is when one gets every thing glued together only to find their stator coating was inferior and failed, ruining a perfectly good piece of mylar as it is not exactly cheap in small quanities.
Here is great thread dedicated to many of the things found suitable for stator coating use,

High strength Dielectric Coatings, fact or fiction

You can vari the bias voltage by choosing different taps along the multiplier stack or you can use a chipamp to power the supply stepup tansformer as I had mentioned earlier.
This would be much easier to do then developing some some sort of switching type.
I took me a couple of months and many blown FET's to develop my circuit into a reliable one.
A chipamp makes this much easier to do.

I made my first supply from a old 340v tube amp transformer with about 12 stages (I think) and was plenty at about 5.8Kv.

Later I added more stages when I started testing coatings and stuff.
But ultimately I used less by the time I got my first panels built and running.
After I had learned more about the coatings was when I was able to build a panel that could sustain a much higher voltage.

If you can get 6v/240V transformers for the step-up transformer stage these may be a better choice.
A 240v type of winding will most likely be one complete winding rather than having two 115V windings that are Bifilar wound.

Bifilar winding's add a lot of stray capacitance to the transformer and there is an imbalance of the voltages across the whole winding when they are tied in series and could cause a breakdown failure.

But you have to be pushing them rather hard in order for these conditions to occur and work very well under normal conditions

As for the diaphragm coating I started out using graphite and this was very messy and many times was unreliable as it didn't bond to the mylar well and it would lift off and the panel would stop working.
It was almost impossible to get a consistent high resistance coating.

This was when I discovered Licron and never turned back way back in 2003 when it first came about.

Many have used other similar products such as Staticide with good results I have not tried this product yet.
There is a whole thread dedicated to diaphragm coatings as Lukas has posted.

There have been a few other substances that have been used from liquid detergents,PVA white glue,antistatic computer screen cleaners to F21 turtle wax products that have been claimed to work a well.
I have not tried any of these yet, But there is always a never ending search for a good inexpensive coating.
All of these are mentioned and discussed in the diaphragm coatings thread.

jer

Last edited by geraldfryjr; 13th March 2013 at 04:19 PM.
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Old 13th March 2013, 07:16 PM   #63
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Thanks for the threads. Licron seems to be popular, but it sure is expensive, 32 for 8 oz aerosol spray can! What coverage can be expected from a single can? as I will need to make several prototype panels and don't want to spend a fortune
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Old 13th March 2013, 07:42 PM   #64
Bazukaz is offline Bazukaz  Lithuania
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Quote:
Originally Posted by portreathbeach View Post
Thanks for the threads. Licron seems to be popular, but it sure is expensive, 32 for 8 oz aerosol spray can! What coverage can be expected from a single can? as I will need to make several prototype panels and don't want to spend a fortune
8 oz can is quite a lot if you apply it thin.
In my case the usage is about 4-6ml/m^2 when applied with a cotton wipe, so one spray can should be enough for several tens of sq. meters. I think that's more than you are willing to build over you life . Surely it has some storage life limitation.
Note that it is important to have a very good contact between licron and copper adhesive strip which is used to supply charge.Otherwise corona can eat the coating near contact point. Apply licron before gluing copper tape and then on top where copper and mylar meets by using a small brush.

Last edited by Bazukaz; 13th March 2013 at 07:49 PM. Reason: Extend
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Old 13th March 2013, 07:47 PM   #65
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Oh, if it would cover tens of sq. meters, that isn't too expensive at all. I didn't want to end up buying can after can after can of the stuff just experimenting.
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Old 13th March 2013, 08:08 PM   #66
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I have had my original can of Licron since 2003 and out of the 3 or 4 small sets that I have made I have rediaphragmed them maybe 2 or 3 times as some had a set of thicker replaceable frames.
And I still have about 2/3's of that same can.
And I have a nearly full can of Crystal formula that I got back in 2010 as I have only used it a few times.
It goes a long way!!

I posted some pictures a while back of one of the original diaphragms that I made in 2003 and it still works today except for the holes that are in it now.
It never wore off even after much deliberate environmental abuse for 7 years.

I have this documented in one of the threads.

jer
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Old 13th March 2013, 08:30 PM   #67
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Right, I will definitely be using it then. A lot of people are saying they have had good results with it and if it goes as far as you said and it lasts for years, then that is proof enough for me

I have enough information I think now to gather some materials together, so hopefully later in the year I can start experimenting. I have a few other projects on I need to get done (conservatory and landscaping the garden) before I can start building any more audio gear, oh and it's always a tough one explaining to the wife why you have to keep building audio stuff! But at least she does appreciate the quality of the finished results, she can hear the difference in quality from most of the stuff I build when compared to a fairly expensive Denon AV amp and Monitor Audio speakers.

She was a little concerned about the voltages present on ESLs as we have a 12 week old baby that will soon be crawling and toddling around, but as I'm and electrical engineer by trade and explained how they work and that the current is very small, she seemed to turn to the idea.

Thanks again. I'll post some pictures when I get around to building.
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Old 13th March 2013, 08:51 PM   #68
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Very good, it will be great to see another successful DIY ESL build!!!

When I first got going everything I saw I would wonder to myself "Hey I wonder of that would work!! ".

I think I spent about $200 on different materials to try only to find that my first set cost less than $20 to build and lasted for nearly 9 years had I not burned them up pushing them past there limits.
Well, I still have one of the those two panels anyhow and all of the other ones I made too!

jer
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Old 13th March 2013, 09:13 PM   #69
tyu is offline tyu  United States
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Quote:
Originally Posted by Bazukaz View Post
Note that it is important to have a very good contact between licron and copper adhesive strip which is used to supply charge.Otherwise corona can eat the coating near contact point. Apply licron before gluing copper tape and then on top where copper and mylar meets by using a small brush.
This is vary true...This is were most of the panels fale..An run the Copper all the way Around the panel...you get the most output out of panel this way...It can be good for 2-3 more db output...
An If you can bild the panels so you can open them...i find after 6monts...thay can lose 20% output from dust..open an clen an it like new panels agin.. Just my 5cent....Good luck

Last edited by tyu; 13th March 2013 at 09:17 PM.
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Old 13th March 2013, 09:48 PM   #70
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Depending upon where you are, Humidity can sometimes be an issue when using copper for a charge ring as it corrodes very easily.

I have always used aluminum tape for my charge rings and connections to the diaphragm and never had an issue with it even after 9 years and have been beat up with road salt.
Even though I don't live in a high humidity area anymore either.

But since then I have switched to using a conductive glue made out of some white glue (Elmers), water, Graphite and a few drops of dawn dish soap to keep it from beading up as it is painted on to the frames.

This method works beautifully and will never ever corrode.

It can be applied directly upon the licron coating or just sandwiched against the coated mylar, either way as long as it is making contact it will work.
Since it is conducting HV the resistance of the material has no effect on the system.


jer

Last edited by geraldfryjr; 13th March 2013 at 09:50 PM.
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