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Hornby class 90 DCC conversion.


96RAF

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i have come into possession of a Railroad Class 90 probably R062, but looks same as the illustrations on service sheets HSS209/273.

I intend to chip it but reviewing on line decoder installation guides it appears you have to disable the switchable live pantograph on this model for DCC.

Why I ask myself. On DC presumably one rail is negative and the other rail and/or the panto are positive. Why can't on DCC the same arrangement be made, I.e. One rail B polarity and the other rail and the panto A polarity.

i don't have/wont need a live panto but the specific instruction intrigues me.

Expert opinion welcomed as always. Guessers and tyre kickers please enclose a CV so I can filter out your advice.

Rob

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Left rail A polarity. Right rail B polarity. Panto B polarity. What happens if you turn the loco round?

The other thing is intermittent contact with the overhead wire, which isn't a problem with all wheel power pick-up on rails, but you only have one point of contact with a pantograph.

I expect it could be done, but I wouldn't recommend it.

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Even the 12"/foot ones do a lot of sparking and popping, if you watch them! (Especially in this freezing weather!). To run an o/h panto pick-up will be very similar to running a loco on dirty track, the splutters will keep 'killing' the DCC control if it doesn't kill the chip!

A long time ago, I did try running an N gauge (Lima) panto pickup with a working o/h wire (home brew), and it wiped out the tv reception, three rooms away!

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Left rail A polarity. Right rail B polarity. Panto B polarity. What happens if you turn the loco round?

The other thing is intermittent contact with the overhead wire, which isn't a problem with all wheel power pick-up on rails, but you only have one point of contact with a pantograph.

I expect it could be done, but I wouldn't recommend it.

The same applies whether DCC or DC physically reversing the loco placement will cause a short between the wheel and overhead pickups.

If I were to persist with the catenary I think I would have to treat the overhead feed as a reversing loop and install an auto-switch module.

I think I will file it under too difficult for now.

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Delete ctheyll and insert the.  This is a standard iOS 8 spelling explosion for me when it hit the C instead of the space bar on the iPad. You'll find that same explosion in at least one other of my posts that I missed until after Edit expiry, possibly more.

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How would you wire the RLM? The OHL would be like a 3rd rail and a RLM has four terminals.

On that basis the OHL would be fixed and the rails polarity switched as per normal RLM scenario.

Any bright ideas on how it could be wired for DCC are welcome.

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Where would you connect the 4th wire from the RLM?

Normal RLM is two wires in from normal track and two wires out to loop track, so I have no idea, please can someone provide a drawing of how to do a DCC catenary and rail fed loco - probably have to use a relay in there on the catenary line.

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