The specifications for the edge connector were recently changed because of this known problem of tab misalignment. 

Nigel

My previous comment was a bit cryptic. Peter seems to have identified a misalignment issue. For those interested the following may be of interest.

From a discussion in Model Railway Hobbyist (Tortoise switch machine connectors - the MRH Forum March 2020):

"Be careful which connectors you purchase. Due to supplier issues last  year Circuitron did a minor redesign of Tortoises, so you also need to  be aware of what version(s) of Tortoises you have on hand. The older Circuitron Tortoise reference specified 0.156” (3.96 mm) center to center contact spacing, where the Changes Coming note on the Tortoise page  (see quote below) indicates a contact spacing of 3.81 mm (0.150"). This  is not a lot, but it is enough to allow for misalignment of the  contacts (which has always been an issue). Circuitron also changed the  width of the PCB edge connector which will now allow the use of Molex or  Molex compatible eight pin edge connectors and which avoids the  misalignment problem." Ken K. 2020

"Because of the width of the connector section of the OLD Tortoise PCBs,  Circuitron recomended using 10 pin connectors to cover the 8 pins and  making no connections to the outer pins. The housing of standard 8 pin  Molex connectors are too narrow to fit over this section of the OLD  Tortoises, and the connector spacing is different. You could always do  what some did and cut or file down the edges of the PCBs.: Ken K again.

From the Circuitron web site:

 The new circuit boards will be made of FR-4 epoxy  laminate and will be GREEN on both sides.  This will provide easy  identification of the newer boards, but other than appearance and  quality, the new boards are very similar to the ones we have been using  for 34 years.  Except for a couple things.  The new boards have a wider,  industry standard connection flange whereas the older tan boards were  undersized.  This may create problems if you are trying to fit a new  TORTOISEâ„¢ into an older undersized edge connector.  But they will fit  fine in any industry standard 8 position edge connector.  In addition,  we took the opportunity to change the hole spacing and added a new row  of holes as well.  This will allow the use of Molex style connectors as  well as the 3.81mm spaced terminal blocks that CIRCUITRON already sells  and uses on our SMAILâ„¢.

Many modelers just simply hard wire them and avoid all of this.

Nigel

Hi Peter

Delighted you got it sorted      :thumbs


"Edge Connectors"   that was a bit of a last minute revelation…….worthy of Agatha

Best Wishes

John 

Thanks for this info Nigel - I had no idea they'd changed things so I wonder if that was the problem all along.

I knew the edge connectors could cause problems although I've never experienced it myself and yes John, I only mentioned the edge connectors to keep you all guessing right up to the punch-line !!   I'm sure, under the same circumstances, Agatha would have done the same …………………….. 

Maybe I had used a pre-change connector with a post-change motor - no idea.

It does highlight the advantages, or otherwise, of stay-alives.  It was only when I ran non-fitted short wheelbase locos over that point that the problem came to light. The "fitted" ones didn't bat an eyelid.  I initially assumed it was dirty track or wheels causing the problem - I'm not too hot on permanant way maintenance, particularly in this "testing" stage !!

As this area will eventually be hidden under the top deck I decided now was the time to make sure everything worked perfectly before doing any further construction.

I'm gradually working my way around the layout ironing out any snags which, given the Covid induced shortage of some necessary replacements, is taking much longer than it ought.

Maybe I should learn a bit more about the trickery Martin mentioned although to my little brain, "relay" still means passing a rolled up newspaper tube on to the next runner …………………………….

I thank you all for your thoughts and suggestions - every one of them has taught me a little more.