[Asterisk-Users] Re: Boards falling out...

[Steven Critchfield]

On Wed, 2004-02-04 at 12:12, Colin Anderson wrote:
> I have used hot glue for many years with no problems. Decent adhesion, but
> can be picked off if ness. I showed this to a systems integrator that had
> problems with shipping PC's upside down and boards would become unseated. He
> used this on thousands of systems and the problem was eliminated. 

Hmm, sounds like something the Digium resellers could do. I can see the
commercial now....

<cheesy announcer voice>
Is your access to <insert local emergency number> important to you. Do
you want to not have to go looking for your tools in the middle of an
emergency. For the low low cost of $29.99, we will throw in a hot glue
gun and 3 sticks of glue to solve all those earthquake related failures.
</cheesy announcer voice>

> -----Original Message-----
> From: Stephen R. Besch [mailto:sbesch at acsu.buffalo.edu]
> Sent: Wednesday, February 04, 2004 10:14 AM
> To: asterisk-users at lists.digium.com
> Subject: [Asterisk-Users] Re: Boards falling out...
> 
> 
> Greg Kedrovsky wrote:
> 
> > I have a TDM40B, 4-port fxs card. Each port seems to have it's own
> > little board on the fxs card. Each little board is not sodered in, but
> > rather "hangs" (I have a vertical case for the server) on what I would
> > call jumper pins (sorry, I'm not a profession geek, just a wannabe). One
> > of my little boards, over time, slides off those jumper pins. I just
> > noticed it this morning. I had to power down, seat it, and power up
> > again. That's a pain. 
> > 
> > We did, though, have an earthquake this morning. That may have shaken
> > things loose a bit. But, it wasn't much to speak of (long, but not
> > strong). 
> > 
> > Has anyone else experienced this problem? What could I do to solve it
> > (seat the little card a little more permanently)? 
> > 
> > Thanks ahead of time.
> > 
> > -Greg
> > 
> There are three issues here, relating to the other posts on this topic. 
>    Don't use loktite. Loktite is what is called an anerobic adhesive. 
> Specifically, it is catalyzed by contact with metal in the absence of 
> oxygen. As such, it will only cure (in the absence of some other 
> chemical activator) only down inside the pin sockets, holding them 
> together. The rest will stay uncured and spread all over other stuff. 
> This may essentially make them a single use contact.
> 
> The silicone is a good bet.  The acid referred to is the acetic acid 
> (i.e., vinegar) released when the monomers in the RTV goo cross react to 
> form the silicone. Once the cure is complete, there is no acid 
> production and what was produced diffuses away. Mild acids are not 
> terribly corrosive to most metals, and not at all corrosive to gold. 
> The types of RTV that don't produce acid may actually produce alkali 
> (ammonia), which is far more corrosive, but also diffuses away readily. 
> Nevertheless, I would stick to the stuff that smells like vinegar.
> 
> Finally, I have found that the best approach is the simplest, when it 
> works. If you can get one of those nylon tie-wraps around the daughter 
> card in such a way as to hold it in place, this is the best - and most 
> reversible approach. Sometimes, there are appropriate holes in the 
> motherboard, othertimes the ty-wrap can be snaked around under the 
> connector - however, don't run it under any other type of component.  I 
> have even drilled holes in 2-layer circuit boards, but I would not 
> advise this unless you really, really, really know what you are doing.
> 
> Finally, if the female side of pin sockets are loose enough to let the 
> dayghter cards fall out, they may also be the source of noisy, 
> intermittent connections.  Sockets of allmost all kinds are notorious 
> for this kind of thing. I can't tell you how many times I have repaired 
> a flakey circuit board by removing the sockets and soldering in all the 
> (formerly) socketed chips. The square pin spring contacts in those 
> connectors are only designed for a few insertion/removal cycles.  If 
> that is the case, you should get a good repair tech. to replace them.
> 
> Good luck and hang in there.
> 
> Stephen R. Besch
> 
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-- 
Steven Critchfield  <critch at basesys.com>