Weak or NO DCS signal from TIU

@GGG posted:

The simplest is when one channel does not work but all the others do.  The worst is none work and LED barely lights or the current draw is high just TIU.  This means a short that is effecting the Power Supply.  So you can pull all the transmit chips and if still present pull the receiver.  If still shorting change the 5V reg, if still shorted, look for round object with lid and deposit TIU in the object.

Yep, this is what inspired me to work on 2 TIUs in the pile that were totally dead. One came back to life, the other is a parts donor. Thanks for this tip as I incorrectly assumed everything was fried (meaning the logic too) and this inspired me to just remove them all (all 4 TX and the RX, and even the 5V reg) before deciding dead or not. That point where you have nothing to lose, it was on the left for dead shelf.

@gunrunnerjohn posted:

You're indeed missing something.  We're protecting the driver chips, but they're 5V parts!  They don't connect directly to the track, there's a host of analog logic and a coupling transformer before the signal gets to the rails.

Thank you, GRJ.  I finally found the correct old thread with Adrian's description of the 22-diode beefy clamp design and the discussion.  Of course, folks like Adrian and you have forgotten more than I know about this stuff.  I think I get it as well as an experienced rank amateur can.  Noting your "design with Schottky diodes and a 1500W TVS" from 2 days ago, and that you didn't get enough interest to do a production run: for some price would you supply, say 8 of those ready to install with instructions and pictures exactly where to solder each of them in a TIU?  I have one brand new and one very little used (test track only) Rev L TIUs that could be protected and will suffice for all anticipated layout needs, and then I'll set aside the one that has been on the layout for years.  Or, I could send the two to you or purchase a couple TIUs from you if you have them, to send them so equipped.  I would want to be sure we were starting with known good TIUs. Our pacific northwest service options are painfully limited and far behind with long waiting times, or we wouldn't do so much of this ourselves.  However it would work best, I'm willing to do it that way.

Thanks, Don