SSlmixed.com Forum

Tech discussion => 4K,6K,8K Series => Topic started by: jwhmca on August 12, 2014, 06:08:44 PM

Title: 82E242 (EQ) intermittent short? **SOLVED**
Post by: jwhmca on August 12, 2014, 06:08:44 PM

Hi Guys,

I have an 4k that has this intermittent short on the 242 EQ. It will blow the 611 +18 fuse. Pull the card out, there is a dead short across the +18 C48 and other things... in a few moments the short goes away...!?!

Diodes, caps, IC's can do this... shot in the dark here, but has anyone had intermittent dead shorts on SSL cards?

Title: Re: 82E242 (EQ) intermittent short?
Post by: Matt Sartori on August 13, 2014, 09:05:00 AM

not really but it's worth replacing the components in that area and clean the tracks and pcb with isoprop before placing new components on.

Mattia.

Title: Re: 82E242 (EQ) intermittent short?
Post by: waltzingbear on August 13, 2014, 06:01:10 PM

I am assuming that you are using a meter to measure R to say the short goes away.

That seems to indicate that some active device is involved as it is allowing the DC charging of the circuit when off. If it was a cap, that could be always shorted. Try removing the chips and see if that makes a difference. Then any other active components. and same test.

If you have a sensitive enough R meter you can sometimes follow the route to the short by watching the very small value of R as you move the probes around. Takes practice and good technique.

Alan

Title: Re: 82E242 (EQ) intermittent short?
Post by: jwhmca on August 20, 2014, 05:59:45 PM

Turns out: It was the "Shrink tubing" that SSL used on the trace side for a couple of add on components... the stuff had grown conductive over the years...

Title: Re: 82E242 (EQ) intermittent short? **SOLVED**
Post by: sintech on August 20, 2014, 06:21:39 PM

Fantastic, well spotted, and a very good tip for us all to watch out for in the future.

Thanks for sharing.

Title: Re: 82E242 (EQ) intermittent short? **SOLVED**
Post by: jwhmca on August 20, 2014, 06:52:59 PM

What about having a "solved" section...? See my post in the comments section.

Title: Re: 82E242 (EQ) intermittent short? **SOLVED**
Post by: radardoug on August 21, 2014, 09:23:46 PM

Was it actually the shrink tube, or had a solder dag punched a hole in the shrink tube?
If the shrink tube went conductive, everybody has a big problem. And tube going conductive seems unlikely. To blow the fuse it needs to be close to a dead short.