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Help finding the problem... grounding issue?

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London

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Hi. I built the attached circuit as a prototype and tested it and it worked perfectly. Its basically straight from this EL driver's datasheet.

I then hand soldered about 200 of them by hand. Sure I had some one-off problems here and there, but for the most part it worked.

Eventually I started having them assembled over-seas and out of every 100 I get between 8 and 15 returned to me because the EL panel won't light up. I've been just replacing them because I've gotten busy, but just now I decided to test the defective ones. The odd thing is that the proper voltage (~85VAC) is getting to the EL panel (pins VA, VB) but when an EL panel is actually connected, it spikes the voltage beyond the panel's range (~136VAC). If I ground one of the pins, the light comes on.

I'm hoping this is a "well duh, its this" to one of you. I really know very little about electronics. The product is only "special" because of the shape of the board for its application, the circuit I was just copying the datasheet. I don't get why they all worked when I hand soldered them and now some don't. I've done a continuity test on every pin/pad and everything SEEMS like its soldered properly. I've tested the resistors and they're all fine. I don't know how to test the other components (caps, inductor, diodes, etc) however on one board I've replaced EVERY componenet except the main chip and nothing fixed it. Replacing the chip fixed it. To me that confirms its a "bad" chip, but then I don't get why grounding and EL pin seems to "solve" the problem (or does it? that's another question... can I ground that pin and send it back or is that potentially causing a problem?)

Any help/advice appreciated. Thanks.

L
 

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Can you give us all the componet values as well as power supply voltages? Maybe the inductor part number would be good as well.
 
SABorn - All 8 of the chip's pins show good continuity but yes, I did re-solder them just in case.

ronv - yes, I can. I'll repost momentarily with that info.
 
I was looking for info concerning ripple current for the cap and I could not find it to see if the cap was appropriate.

Does an EL panel require a grounded plate behind it?
 
Have you asked Supertex for help? I find mfgs of specialty ICs most helpfiull in the support of their product. E
 
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