Capacitor discharge unit

JPS,

The capacitor discharge unit itself is the means to keeping switch machines from getting sluggish.  If they still don't snap well after inserting one of them in the circuit, like the Miniatronics PDC1, then you have a substantial mechanical problem with the machines, and/or linkages and points as well.

Miniatronics has not posted its instruction sheet for the PDC1 online, and I don't personally have a paper copy to review it, but your hunch on supply voltage is likely right on target.

What it has published is this:

Click here for more: Miniatronics Super-Zapper Capacitive Discharge Unit)

As a rule of thumb for all electronics I wouldn't go more than 10% over the recommended operating voltage in order to be safe (and many people say 5% to be extra safe).

As a result, applying 20 VAC probably killed it.

And, it would be a good idea to check out the mechanicals of your switch machine installation before proceeding with replacing your PDC1.

Mike

I used one from Dallee electronics in Leona PA.  Used it on a diode matrix board which would fire a multitude of NJ switch machines with one push button to align as many turnouts as needed upon entering a particular track in a large passenger terminal.

CD systems are great and usually very dependable, capable of long life.   We used them in racing (totally different world) for years in very rough salt water situations.

I built my own over 15 years ago from a book  called "Easy to Build Electronic Projects for Model Railroaders" by Peter J Thorn  published about 20+ years ago by Kalmbach. The book is available new and used on Amazon. It took less than $10 in parts and under 2 hours to build.

I use NJ Switch machines.  I power them with  14 VAC step down transformers which I also use for accessories.

Thanks for all the input.  Over the years I lost a bunch of machines with burned out coils which jammed for whatever reason.  I was able to rebuild most of them.  It takes a little more juice as they are under table and operate with a swivel linkage.  Some of my old wiring might be weak, and tripping them with my AIU saps more power.  I even wound up stretching the springs on some of them.  I was afraid the 20v output might overdo it.  When I get the replacement I'll use the variable output of the KW to bring it down.  In my mid 70s I really don't relish crawling under the table to fix switch machines much. 😐