RS-232 Serial I/O Board - Message

Saturday, March 24, 2001

Hello to all of you,

Hopefully, you all have your printed circuit boards for the RS-232 I/O board project in Nuts & Volts (unless you are one of the ones that just ordered one of the last few extras that we had ordered).

After we received the boards, I immediately built one up and tested it out to make sure that it worked correctly. Everything worked well. Hopefully, your board is also fine. I am sending this notice out just to let you know that I built up a couple more boards on Thursday night, and I found that each of these two boards had a tiny, very thin short from Vcc to a top-side trace (it was a different trace on each board). They were so thin that it was almost invisible to the eye, but it caused the board to not work correctly. Since it happened on 2 of our boards, it is very possible that there are other boards that were sent out that have a similar problem.

Of course, we are not too happy with the board manufacturer at this point, but I'm not sure there's much we can do about it except give them a lecture on quality control. Anyway, if you are experiencing problems, then please contact us about it.

For your information, here's a good way to take care of these shorts: based upon what the board is doing, the signal that is shorted can be identified. A scope will help in identifying which signal is not acting correctly, and a multimeter can be used to verify that there is a short. Once the shorted trace has been verified, don't bother trying to actually find it. From our experience with these 2 boards, it is VERY hard to see the short since it is so thin. Instead, just blow the short like a fuse by sending some currect through it with a power source (hook one power lead to VCC, and the other to the shorted trace -- with the board powered off and totally disconnected, and with all the chips removed from the sockets). It won't take very much current to blow the short.

We have no way of knowing how many boards have a problem. Chances are, there are a few out there that have this problem. Even if you are able to take care of the problem, please let us know about it so that we can determine the magnitude of the problem when we contact the board manufacturer. If you are having problems, then we may be able to help you out via e-mail if you describe what is happening. If you simply can't get it working, then you may want to send it to us so that we can get it going for you.

We apologize for the problem, and we do not plan to give this particular board manufacturer the opportunity to mess up any more boards in the future.

As usual, visit the web page www.winford.com/publications/serial/ for any updates and new information.

Regards,