RailPro > RailPro Specific Help & Discussion
New install issues
Blueleader:
I tried twice and it didn't change anything. Got the whole kit boxed up and ready to send back to RP.
--- Quote from: nodcc4me on September 11, 2017, 07:42:49 AM ---Having never seen an LM melt down, I'm wondering if there is a short in the 9 pin locomotive plug?
Try pushing the reset on the HC2. I have had some weird happenings that were fixed by doing that.
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Alan:
--- Quote ---Having never seen an LM melt down, I'm wondering if there is a short in the 9 pin locomotive plug?
--- End quote ---
Or elsewhere in the loco wiring. Correct DC operation would still work if the short were in a non-motor wire.
--- Quote ---Though RailPro has temperature detection it appears that does not equal over temperature protection!
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Unless track power was also being supplied directly to the blue wire and/or the new LM3 ground pin. The module may have shut down but the juice kept flowing because of the power connection downstream from the protection circuitry. Same problem we discussed with attaching keep-alives using the new LM3 ground pin. In this case the 56 may have been a never-exhausting keep alive!
A LM has at its heart a PIC microcontroller. I can find no reference to the PIC family having integral thermal shutdown. The data sheets specifically say the PIC will be harmed if operated beyond spec maximums leading one to believe there is no integral shutdown. I did however find many references to using PIC in conjunction with power management chips that do have thermal shutdown. I wish I had taken pictures back when I took the case off an LM. Can't remember what other active components there were other than the microcontroller. It may be that an LM doesn't have thermal shutdown. Might be too nosy of a question to ask Tim.
Blueleader:
Melted LM3S
Alan:
It appears the case melted above the SMD tantalum capacitor (A337J). Tantalum caps get very hot when reversed biased or sometimes even explode.
G8B4Life:
--- Quote from: Alan on September 11, 2017, 08:42:03 PM ---It appears the case melted above the SMD tantalum capacitor (A337J). Tantalum caps get very hot when reversed biased or sometimes even explode.
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I had another thought tonight while resting my mind (read dozing) before checking back here, which I'll get to. Alan, the melting of the case is on the 6 pin end, not the 9 pin end where A337J is. My theory is the audio amplifier was being over driven (too little speaker resistance?). Given that the melting of the case is exactly in line with the speaker wires on the 6 pin JST gives some credit to my theory. On the reverse side of the board, ACN E AL (10 pin IC top right of picture of board underside) is the vicinity of where the heat was generated. The melt even has the same shape as ACN E AL.
- Tim
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