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Message started by Penguin on Aug 8th, 2017 at 5:54am

Title: A1 panel arcing over
Post by Penguin on Aug 8th, 2017 at 5:54am
Hi Everybody, I have not been around here for a long while... One of my panels started to arc over, i used Dow-Corning 748 sealant at the place where i found it to arc over, it seemed to have fixed the problem for a while and now I have a new arc over in the near vicinity of the first place.  Is this something normal?  Do you find that once the panel starts arcing it is a loosing battle and it will just keep migrating to new locations?  Is there a way to determine this by some sort of inspection where the insulation is weakened? 

dee
;-D

Title: Re: A1 panel arcing over
Post by Jian on Aug 12th, 2017 at 2:43pm
One of my speaker, 945, is starting to arc, too. I guess the panel is going to fail one day. I will try to use silicone to see if I can cure the problem. Otherwise, I donít know what I can do except sending the speaker back to Sound Lab.

Title: Re: A1 panel arcing over
Post by HJP on Aug 13th, 2017 at 5:46pm
[quote author=75683F0 link=1502196863/1#1 date=1502574226]One of my speaker, 945, is starting to arc, too. I guess the panel is going to fail one day. I will try to use silicone to see if I can cure the problem. Otherwise, I donít know what I can do except sending the speaker back to Sound Lab.[/quote

IIRC, there is a "fix" in the archives of this web site outlining how to re-insulate a stator wire breakdown.  If you are experiencing charge migration between a stator wire and the diaphragm (not stator to stator), its 95% sure its the dialectric sleeve on one of the stator wires in a specific place experiencing breakthrough leaking.  Re-insulating this place will usually solve your problem.

Arcing on the other hand is a violent "short" between a pair of stator wires of opposite polarity (between one of the rear and one of the front wires in a specific place) through the diaphragm.  This will burn a significant hole in the diaphragm and usually necessitate its replacement as well as the offending stator wires.  This is immediate and catastrophic (and somewhat unusual).

Most likely you are experiencing charge migration and leakage breakthrough as previously explained which in all likely hood can be fixed.

If not in these archives, it definitely exists and is documented somewhere, perhaps on SoundLab's own site.

Title: Re: A1 panel arcing over
Post by Penguin on Sep 15th, 2017 at 12:16pm
tried the silicone treatment....the arcing happened where the yellow wire is connected to the copper ring, it was rather difficult to et the goop behind the strator wires and don far under the frame, but the arching is gone, now i get a rushing sound and a light pop when i turn up the bias.  I still must have a leak, but how do i locate it?  no visible clues.


dee
;-D

Title: Re: A1 panel arcing over
Post by Penguin on Sep 19th, 2017 at 4:38pm
Still making strange noises and it discharges somewhere.  Any ideas how to locate it?  is the re a tool of some sort to detect it.  Use a funnel and tube, any suggestions?  In total darkness i cannot see any flickering anywhere.  Can it be  under the frame somewhere?


dee
;-D

Title: Update on the arcing over
Post by Penguin on Oct 10th, 2017 at 7:16am
So located the popping sound the culprit was the bass transformer.   The bass transformer was replaced....i can now properly bias the panel....but if i crank it up real loud, i still get an arc over. so i am limited as to how loud i can play them.  kinda annoying.  The question now, how to isolate this.  I put the whole thing together...and still have this arcing.   It appears that the arcing happens on bass impulses.  maybe just use a drum recording, any have any other ideas?

dee
;-D

Title: Re: A1 panel arcing over
Post by HJP on Oct 11th, 2017 at 11:40am
Dee,  In my experience, if its charge migration between a bad stator wire and the diaphragm, you should be able to see the location of if you turn off the lights at night in a darkened room.  Turn up the volume enough to start the leakage with a suitable recording (drums, whatever brings it on).  You should be able to see the sparking. Once you locate the spot, the fix I mentioned earlier involves a new longitudinally split insulating sleeve a couple of inches long that gets inserted around the offending stator wire and is set with an internal insulating adhesive (could be silicone, can't remember) inside the sleeve.  Can't remember where this fix is located but it does exist and is very detailed step by step specifically for SoundLabs.

Just using silicones by themselves around the offending wire is likely to be only temporary.  I've done this many times myself with Infinity Servostats years ago but eventually they started to leak again.  The sleeve repair should be permanent.  Otherwise, I'm afraid the speaker would have to go back to SoundLab.

Title: Re: A1 panel arcing over
Post by Penguin on Oct 12th, 2017 at 7:50am
You said sleeve?   That sounds quite intriguing....

What is the sleeve material you use?  What is the wall thickness you recommend, and the material?  Any sources for it?  The Published fix from Soundlab only mentions the use of RTV on both sides of the panel.  This is one of the best advise is had in a long time BTW.

dee
;-D

Title: Re: A1 panel arcing over
Post by HJP on Oct 12th, 2017 at 10:22am
Dee,

The repair I have alluded to answers all your questions.  I wish I could remember where it was to guide you to it.  Have you checked the old archives on this site?  It might be there.  So, unfortunately I don't have any definitive answers.

I can tell you that a Teflon sleeve of appropriate diameter to fit around your stator wires would definitely stop the charge migration.  Its one of the very best insulating materials out there for this application if you can find one that would fit.  I think a silicone filler inside it should be OK since the Teflon would be the primary dialectric.  SoundLab may be able to help you with this too.  You might give them a call.

If you have a newer panel with the smaller stator wires (older panels were 20 wires per facet, newer ones were something like 28 and smaller in diameter, not sure but much more than 20).  The reason I mention this is, if you have the newer panels with smaller wires, you may be able to get some insulating sleeve material from SoundLab made for the older thicker wires that would be large enough to wrap around your smaller wires (if they still have some??).

Good luck.

Jerry

Title: Re: A1 panel arcing over
Post by Penguin on Oct 12th, 2017 at 4:17pm
Thanks Jerry,†

I think Capton or Silicone Rubber is more commonly used in high voltage wires.† Since there is not much room between the older thicker wires i need to get some thin wall small id teflon tubing and split it.† i have 1/8" od teflon but i think it is rather thick walled PTFE tubing.† i saw 1 mil Capton tape that is 7500 Volts† i was looking for small tubes with 2 to 5 mill wall thickness but no avail.† The original place where i had the arcing is where the copper perimeter foil is attached to the yellow plug feed wire, not really an active area of the membrane, i had no qualms about filling it up with RTV.† RTV has a dielectric strength of 10 to 18kV/mm† insulating PTFE film is around 60 to 170 kV/mm.† I assume if i fully fill the cavity between the stator and the membrane with RTV i can withstand about 30 to 48 kV of potential difference.† At that point the membrane is immobilized at is quiescent position. Assuming max 12 to 14 KV membrane bias, and† about 6kv peak for full power into the speaker. (38 V into 4 ohms, and 1 1:90 step up RMS to peak * sqrt 2)† i have a 30% safety margin for breakdown voltage just using RTV.† †But for an active area of the panel, the sleeve would be much better since only one side has to be altered.† †Has anyone tried self adhesive Capton tape?† Two layers wold be good for 15 kV.

dee
;-D

Title: Re: A1 panel arcing over
Post by Penguin on Oct 16th, 2017 at 1:28pm
Mystery solved....the last arching was not the panel, but i had some of the speaker cable terminals very close to each other, on high volume it arced.  Was strange, but i saw it in the dark. I reset the terminals, all is good now.


dee
;-D


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