Lenz Silver Plus decoders

[Budgie]

This all started a few months ago when I was running a rake of Hornby 8Hal, and I discovered that all four motor bogies were being driven at different speeds. Actually I was using two different decoder types by the same manufacturer, one of which is no longer on sale, and I was amazed by the different speeds I was getting between the two types.

 

So I bought an ESU Profi Prüfstand decoder tester, and immediately improved it by soldering a voltmeter across the motor terminals. I then started testing all the spare decoders I've got in stock, and keeping a note of the output voltage supplied by each decoder given a standard 16 volt DCC input.

 

Most of the decoders I tested measured between 14.5 and 15.6 volts. The ones I mentioned being troubled with (not Lenz) measured 13.9 volts, and then, of course, there's Lenz.

 

I have three different Lenz decoders, a single silver mini, a trio of silver direkt +, and a quincunx of silver 21+. There is no problem with the silver mini, which one would expect as its name does not include a plus sign, and its output voltage is 15.3. However, the other two are causing problems. The maximum voltage I can get out of them in 9.6-9.7 volts, or, if I press F3, 5 volts (this last one is not a problem: it's the shunting speed). I'm wondering why this should be the case; apart from the shunting speed there is no mention of this decoder's less-than-normal maximum speed anywhere in the documentation.