https://ogrforum.ogaugerr.com/topic/wea ... 1160839697
I can only imagine the firestorm if it had been Lionel
"With Adrian's extensive help (Thanks again, Adrian), we've landed on the beefier TVS as shown in his original post of the back of the TIU with the four yellow sketched diodes. His daughter card design is probably the "silver bullet" fix but isn't exactly practical in a production sense. That's why we are going with the four larger TVS's attached to the signal transformer on the back of the TIU PCB.
All new Rev L TIU's produced going forward will contain these TVS's. In the field we have a Service Bulletin that was released today, in fact, that outlines removing the old mod (wimpy diodes) with the larger ones. While Adrian noted that there were still occasional failures, it's a balance of fixing it without re-designing and laying out a new PCB vs. applying a solution that gets most TIU's serviceable long-term.
From MTH's Service perspective, we will be adding this mod to all TIU's that arrive in for service with blown xmit chips or any condition that would indicate such. Additionally, this mod can be applied to any Rev TIU you have in your inventory. The vast majority of TIU's we've seen come through Service as well reports from the field have been on Rev L TIU's. Only the Rev L TIU's have the old mod applied.
For those of you who are ASC's you will have this service bulletin. I've also shared it with Barry Broskowitz so he can post it on this forum to let those that have the ability apply it to their TIU's. MTH isn't carrying the component at this time so you can get it from Digi-Key per the bulletin.
NOTE - If you are NOT an ASC and you attempt this mod and damage a TIU that is under warranty, it will void the warranty.
Thanks,
MTH"

