The Issue is the points

Marc, the issue with your proposed wiring scheme is tying the point polarity to the changing frog polarity.  Given Shinohara's use of points soldered to bridging plates, that is your "best" option if you retain those bridging plates.  "Best" is not good, though.  Much better would be electrically isolating the points from each other and tying each point to its stock rail.  This requires both mechanical and electrical work.  The new hinges can be rail joiners for the point to closure rail attachment.  The point end could be done with a new printed circuit board tie with a gap (or two gaps for a stronger center) between the point rails.  

The electrical issue with point assemblies such as this Shinohara switch is that any bridging of the gap between the stock rail and point can cause a short.  It turns out our old DC-analog systems were far more tolerant of such shorts than DCC--usually because we use a number of very fast-acting circuit breakers or other electronic devices with DCC.  

Though almost all of my switches were either purchased as "DCC ready" or built that way, I did have to modify a Shinohara wye switch in the fashion I suggest.  It works quite well now.

Bill Decker, espeecascades.blogspot.com

Yep, the points are a problem

Try this first

   Just install it with insulated rail joiners at the two rail ends coming off the frog. That way the points switch polarity all the way thru the turnout. If your wheels are all in gauge they'll clear the points and not cause a short. These type turnouts were used this way for decades. If it doesn't work out as power routing you can remove the points and install them with an insulated throw bar,then decide how to gap and power the frog, but it's a lot more work and might be fixing something that's not broken.....DaveB

Thanks all

Thanks all for your remarks, sorry I don't know well this kind of turnout since I exclusively model in N scale and don't know the details of the construction and issues of these old turnouts.

In fact I made this quick sketche to show how to do them DCC friendly, because they are so much topics about old turnouts which are proposed on the forum and are still on the way right now.

I just find this could help many of us which are asking to use such old turnouts.

Course I have  suspect the point would give trouble like short knowing they are in "one assembly" without electrical isolation for each side, a bad ingenering for DCC use.

Rebuilding the point assembly seems the only way to make them safe.

In conclusion this is the work list,

1. Removing the whole point assembly, pop off the rivet tab, removing the throwbar

2. Unsolder the  small riveted  tab and dismantle the throwbar

3 . Joiners in place of the little riveted tab for the points and closure rails  and jump wire between them

4. A new throwbar, made of PC ties, point soldered with NMRA tolerances.

5. Jump wire between closure rails and stock rails

6. Isolate the frog with gap cut in the rails as show in the picture.

Remarks are sure welcome.

Did that with an old curved

Did that with an old curved turnout, works great now.

Here is how I resolved the

Here is how I resolved the issue using a portion of guitar strings and copper clad board cut to size. Mine were modified in 2008 and have worked without issue so far. I experimented with strait and looped bridges.  You can just make out the loops at the 9th tie from throw bar.

Gaps cut before and after frog. The black tie just before the frog is powering the point rails

Flip side

Some people said using guitar string would cause issues and derails. Never did. I did not trust rail joiners in the long run.