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I discussed this on another thread and have the same issue on a second Rev L TIU.  When engines cross onto the blocks controlled by a Variable 1 channel set to fixed they slow to a crawl.  Input voltage is 20 volts on the Var 1 channel and the output voltage is 12 volts under load.  When I disconnect the output and measure the voltage at the output of the TIU its 50 volts.  It is not my meter  Tried five different meters in increased quality.  This is the second TIU that has had the exact symptom   Anybody here any issues with the Rev L?

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Ben, our experience with TIU failures at the Boston Metro High railers is similar... Most of the failures (whether Rev L TIUs or other models) have been Power FET failures... The TIUs that have failed that were still in warranty we sent back to MTH for repair...  Those that were out of warranty we repaired ourselves...  Our chief engineer has gotten very adept at replacing the power FET transistors...  I think it's true (at least anecdotally) that the replacement power transistors have not failed after installation... Somewhere I have the transistor types we have used... As soon as I find them I will let you know...  Also I will talk to our Chief engineer and see what additional information he can give me... 

 

The last TIU failure we had concerned loss of DCS signal; that went back to MTH for repair (replacement of the DCS signal generator chip)...

 

The fans we have installed on our TIUs at the club have also helped to reduce (but not eliminate) TIU failures at the club...

gunrunnerjohn,

 

it might be a couple of days before I have the info from our Chief Engineer...  But I have the data sheets at home which I will pass along to you after I crsss check with the Chief!!  If I remember correctly we got the info from reading the writing on the transistors themselves... Also, if I remember correctly, they are some kind of IGFET...

 

Haven't been able to locate the MTH part numbers in all my documentation.  They do not have any PN listing for TIU's on the website either   Jim I will appreciate the numbers too!  Plan on stocking these as it seems the Rev L has more issues with them than the previous models we used.  We installed the fans on these guys as per your pics too Jim  We haven't had any meltdowns as we did previously.  They help alot.

Dave

I saw some pics that Jim Queenan from the Boston Metro Hi-Railers club posted   One of them had their TIU's showing a squirrel fan from a personal computer mounted above the TIU in a special cradle hence cooling it down while operating.  Large DCS installs pull alot of power through the TIU's and it caused meltdowns when all lines were operational.  I didn't use such a high tech installation.  I didn't use any kind of cradle  I just took a 4 inch squirrel fan and taped it to the top of the TIU.

Muffin is a brand name that has been assigned to the type like Xerox for copying. There are many manufacturers today. If you have a desktop computer there are likely 2 or three inside or attached to the case or power supply. The vary in size from under 1" to 4" and larger square. I suspect they might be found at Radio Shack or if you have an old unused computer you could take one from it. The computer models run on 12 V DC but larger ones operate on 120 or 220 V AC. Google muffin fan and you will see what they look like.

 

Pete

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