Acoustat diaphragm - damaged coating - Repair - diyAudio
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Old 31st July 2014, 09:21 AM   #1
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Default Acoustat diaphragm - damaged coating - Repair

Oh oh...

I bought 8 pannels second hand, washed them 'as usual', and discovered 'holes' in the lower area of the coating. I can see through the diaphragm, two nice windows about 1 to 4 cm in diameter. First time for me...

I checked the HV with my probe : there is no more conductivity/HV in that area...

I repaired one of them with a silver liquid made for the auto's glass heating system repair... Works -the HV comes back in the repaired area-but I've not any confidence in the robustness of my repair, and the resistivity of this product is almost zero...

By 'luck' the area is close to the side of the pannels so I can remove the wires for any surgical intervention ...

Any idea ?

PS : I'm suck at computer, and could not post any picture on the forum. Look bellow for the location of the defects. Same location for all damaged pannels.


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Old 31st July 2014, 09:28 AM   #2
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Yes...
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Old 31st July 2014, 09:40 AM   #3
SY is offline SY  United States
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You do NOT want to use silver there! The coating needs to be very high resistivity, which generally means carbon, and very thin. This prevents charge from migrating.
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Old 31st July 2014, 12:50 PM   #4
tyu is offline tyu  United States
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I have Acoustat panels with 1" holes....that still work great... cant hear any diff.. an thay dont get biger......
less there Big.....play frist see if you hear...the fix my be wrose than playing with the holes....
i have had over 20 Acoustat panels in 30years....these panels are Vary hard too Kill.....i just pik up panels when i can.............good luck

Long live Acoustat panels...................
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Old 31st July 2014, 09:19 PM   #5
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Hmmm...that's the first time that I've seen the coating come off an Acoustat panel. Based on your photo, it almost looks like some of the coating was removed by means of a solvent, rather than losing adhesion to the substrate. I wonder if someone tried to clean the panel with a solvent, or a solvent got spilled/splashed on the panel. Who knows...many years have passed since its manufacture.

In any case, any attempts at repair will likely result in a worse problem. Using any sort of metal-bearing liquid as you described is not a good idea and is very much the wrong resistivity - it could even lead to arcing in that area.

As Tyu suggested, listen to the panel first. Although certainly not perfect, the defect may be hard to detect, especially if the panel is with a larger array of panels.
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Old 1st August 2014, 06:37 AM   #6
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You could use Licron to recoat those area's.

FWIW

jer
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Old 2nd August 2014, 11:50 PM   #7
john65b is offline john65b  United States
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I was just going to suggest licron crystal also - is there an issue getting the licron on the louver and wires? Will it become "charged" if sprayed? I guess as long as the diaphragm does not collapse onto the louver/wires its ok...
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Old 3rd August 2014, 12:02 AM   #8
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I don't think there would be much of an issue.
As long as you can get it in there to wet the diaphragm you might be able to get in there with a small brush to spread it around to coat the bad area.

Due to the construction it would be difficult to make a bridge that would cause any leakage to the stators that are heavily coated with PVC.

You can also spray it into a small container to use for coating with a small swab of some sort and this would cut out any chance of overspray getting anywhere that it should not need be.

FWIW

jer
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Old 3rd August 2014, 12:42 AM   #9
tyu is offline tyu  United States
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As Jim powers from ML told me in the 90s .............thay never wash panels....thay use 30-40lb compresset air .... but most people dont have air....so wash ....why not ML sales panels....

Jim,s not makeing any more Acoustat panels!
i did wash my panels but i stopet.....like this panel the coating well come off now that the panels are older..... 5kV 24/7 for years...in the heat....cold...wet.....this is what i found.....
I stopet because i would rather have a working panel than a cleaner one.....with less output

this is not all crud in the pic....the dark is some coating


long live Acoustats....................
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Old 2nd June 2015, 10:20 AM   #10
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... Thanks for the precise answers. I could not to find the Licron Crystal in France, so I keep on looking for and otherwise will have ship it from the US. Sadly I already applied the 'silver coating' in the damaged areas.

The Spectra 44 work nicely. All the mods done, -including the heavy and rigid frames- gave to them dynamics which make them sounding a little less 'ESL'. Result is good, in the 15/20 k$ range would I say. I also modified the louvre so it is less directive. Works good too.

I also damaged a pannel while trying to glue a defective HV wire.... The wire is now glued to the diaphragm. This pannel I will sacrify (!) and try to change the diaphragm with the infos given by M.James. I'll give you news ....

Regards,
Mathieu
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File Type: jpg Spectra44-13.jpg (582.6 KB, 36 views)
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