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Old 28th May 2010, 12:42 PM   #11
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Hi Paapt,

Please do not give up so easily. Are you using the coating material from ER Audio? You can clean up the coating using Acetone and redo the coating. Please read the link: Jason's DIY Audio: DIY Electrostatic Loudspeakers / ESLs - The Diaphragm Conductive Coating

The link shows a mistake of rubbing too thick coating which might be the opposite of what you have done.

Rob at ER Audio is a very nice person. I'm sure that if you ask him, he will be glad to help you.

Wachara C.
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Old 28th May 2010, 05:44 PM   #12
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Quote:
Originally Posted by JonasKarud View Post
Measure the voltage over each rectifier diode, the voltage here is about 5250 divided by number of diodes. Use caution, HIGH VOLTAGE!!

It's a fairly common fault that one of the capacitors on the HV bias board
is "open". I always change all the caps and rectifiers on these boards when I refurbish Esl 63 speakers.
The way I read this is to only measure across one diode at a time, so the full ~5kV is not actually measured directly?
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Old 29th May 2010, 06:06 AM   #13
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Quote:
Originally Posted by Tosh View Post
The way I read this is to only measure across one diode at a time, so the full ~5kV is not actually measured directly?
Do not do this. Diodes shall be checked on unpowerd unit only. Give it enough time to discharge.
HV diodes may have high forward voltage drop and sometimes can't be checked with simple multimeter.
You may check the voltage across HV supply though.
Make 1GOhm resistor out of 20 5Mohm resistors, minimum 2W rated. Connnect them in series.
Make a shunt out of two small signal diodes like 1N4148. Connect them in anti-parallel.
Put one end of 1G resistor to the hot end of multiplier, tie another end to first terminal of your shunt.
The remaining end of the shunt goes to the cold end of multiplier.
Now connect microampmeter to the shunt terminals.
You are ready to go. Power the unit.
Current through the resistor you've made is proportional to the voltage.
So @ 5kV and 1G you will read 5 microamps and so on.
Alex
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Old 30th May 2010, 01:17 PM   #14
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Quote:
Originally Posted by paapt View Post
Unfortunately no. My multimeter does not go to the 5000V range.
You can buy a second-hand high voltage probe like this one: 80K-40 High Voltage Probe
They were very common at a time when some people repaired TV.
Now that CRT are gone, you can find some for not much money.
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Old 30th May 2010, 05:12 PM   #15
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There is a mistake in my previous post - the total value is 100MOhm, for sure and 50 microamps respectively.
Alex
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Old 30th May 2010, 06:28 PM   #16
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Quote:
Originally Posted by alexberg View Post
Do not do this. Diodes shall be checked on unpowerd unit only. Give it enough time to discharge.

Alex
Can you please give a reason why not to measure each diode separately, I've done so as long as I can remember. If you find a faulty voltage over a diode, its either this diode or one of the capacitors connected to this diode, or both, that's faulty and needs to be replaced.
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Old 30th May 2010, 06:40 PM   #17
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Jonas what you describe is exactly how I check Acoustat supplies for problems.
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Old 31st May 2010, 03:09 AM   #18
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Quote:
Originally Posted by JonasKarud View Post
Can you please give a reason why not to measure each diode separately, I've done so as long as I can remember. If you find a faulty voltage over a diode, its either this diode or one of the capacitors connected to this diode, or both, that's faulty and needs to be replaced.
Sure you can do this.
Usually isolation on mutimeter is good enough no to get shocked (I do not imply electrocuted).
I would not recommend to do so not knowing how cautious that person will be.
Even small shock can force you to do really fast unpredictable movements - which is rather unsafe.
Alex
Sorry my background is power electronics...
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Old 31st May 2010, 08:52 AM   #19
paapt is offline paapt  Portugal
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Quote:
Originally Posted by alexberg View Post
Sure you can do this.
Usually isolation on mutimeter is good enough no to get shocked (I do not imply electrocuted).
I would not recommend to do so not knowing how cautious that person will be.
Even small shock can force you to do really fast unpredictable movements - which is rather unsafe.
Alex
Sorry my background is power electronics...
Hi again,

I apologize for not understanding you in a completely clear way.

Shall I understand from your words that I may check the voltage between the legs of one diode using a common 1000V probe IF AND ONLY IF I am careful?

(I have a degree in Electrical Engineering but have to say that my specialty is computing, not electronics and especially not high power electronics. Thus I must be extra careful about this.)
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Old 31st May 2010, 10:03 AM   #20
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Yes, thats right, measure each diode separatly with an ordinary digital voltmeter, it shall be around 600 volt DC, slightly lower at the end of the ladder, sligtly higher at the beginning of the ladder.

To play it safe, try to use only one hand when you measure, put one hand in your pocket!

More info:

Quad ESL63 electrostatic speaker service diagnose repair schematic manual

Last edited by JonasKarud; 31st May 2010 at 10:06 AM.
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