HM7000 21pin decoder - Fitting - which way up?

[Bulleidboy]

Something I learned today was that the HM7000 21pin decoder will fit and work in a loco whichever way up you fit it. There is obviously a normal way, but if you have to turn it over due to a different pin configuration it will still work. I was told that it is stipulated in the NMRA rules(?) and will feature in the "manual" at some stage.

I found this out after finding that the 21pin configuration in the new R30283 Coronation 46220 is different to those in the 9F (also requiring a 21pin decoder) and the 21pin decoder would only fit in the Coronation if it was turned over from the usual fitting position. I have now done this and it works perfectly.

[Fishmanoz]

This doesn’t seem to make sense. The decoder has one only 22-pin socket on one side which fits into a plug in the loco.

If you turn it over 180 degrees, there is no socket to plug into.

If you turn it around 180 degrees, the pins 21 and 22 positions which are the loco pickups and are at one end of the plug will not match the correct socket positions so the decoder will be both unpowered for BLE operation and not receive any DCC power or signals for DCC operation.

See pages 21 and 22 of the famous manual.

Edit - OP has amended his post now so please ignore mine here and look further down.

[SteveM6]

I’ve seen BB’s pictures and the schematics from Customer Services - he is correct, NMRA allow for the upside down figment as it can give a fraction more clearance.

[Bulleidboy]

The top picture is the Hornby 9F 92220 Evening Star with the 21pin socket, the one below is the Hornby Coronation also 21pin. You will see that the Coronation pins are different to those on the 9F, and so the decoder would only fit the Coronation by turning it over.

[96RAF]

Ref NMRA spec and compact or rotated plugging..

The decoder famous manual will be amended to better show these options.

[Fishmanoz]

Aha, now I get it. I wasn’t able to see that the socket holes go right through the PCB from the current photo in the manual.

Nor does it mention the alternative version of the socket for upside down mounting. Glad it’s being fixed.

And interesting the 21TXS will fit that way given the double-sided component mounting.

[Bulleidboy]

Sorry Fishy, my original posting was not too clear, so I have amended the wording. BB