I did not fry the Sprog II. It still works.
The main web page for Sprog (http://www.sprog-dcc.co.uk/about_sprogII.shtml
) says --'SPROG II requires a regulated DC power supply of 12 - 15V.'
FAQ (http://bbmgroup.home.comcast.net/~bbmgr ... q.html#Q15
'A regulated power supply is required giving 12 - 15V DC. No NMRA conforming decoder should require more than 250mA during programming. Some decoders will draw more than this momentarily during power up and the ACK pulse generated by pulsing the motor could be more than this, depending upon the motor. We recommend a supply of at least 500mA, as available from this site. We supply as standard a 1.25A supply that supports even those higher power (especially sound) systems that take a higher inrush current.'
The power supply I tried with the Sprog II is rated at 14 volts 700mA, well within specified limits. Also, the Sprog II has short circuit protection.
The trains run better with a 14 volt supply. This experience has shown me that the standard Sprog II power supply is okay for programming but not ideal for running TT trains because the 12 volt supply is a bit too low. Since I usually operate trains on just a shelf layout in my apartment there are few demands on power. And usually at the train shows we use Bill Dixon's Digitrax system. The few times I used the Sprog for operation at the train show it did not deliver as much power and speed in the trains. Right now I'm using a temporary oval on the living room floor which has a slight slant and with the standard 12v power supply and continuous running the trains slow down considerably on the slight uphill.
I did not fry the Sprog. The Sprog was misbehaving before I tried the 14 volt supply. I'm not sure whether the problem lies with the Sprog or the decoders. Right now I can run trains with JMRI DecoderPro but not with JMRI PanelPro. I'm not the only one with the problem. There is a discussion of this here --http://uk.groups.yahoo.com/group/sprog-dcc/message/690
---'I set up a loco with a brand new decoder this afternoon. It worked perfectly in program mode, but not in command station mode. I even had it on the same track in the same location and switched between the two modes.'---
When I use a Hornby Elite controller instead of the Sprog I can run the trains with either DecoderPro or PanelPro and it works with the Android tablet as a wireless throttle. The 15 volt power supply improves performance of the trains. The Elite sometimes can be unpredictable in responding to commands over USB and that's why I don't like to use it. That is also a well known problem with the Elite.
The other possibility is that some of my locos have Digitrax decoders. They are DN135 and JMRI doesn't list the DN135. For programing DecoderPro wants to choose DZ143 which I think is a Z scale decoder. When I pick the DN143 things seem to work better. But now there are so many variables it's difficult to figure out exactly what's going on. The one Kuehn decoder I bought works beautifully and that's what I'll buy from now on.
Finally, another thing to watch. The terminals on the Sprog get stressed from usage. I was having problems with the USB connection. These problems occurred way before I tried the 14v power supply. There were no signs of anything wrong on the circuit board but I re-soldered the four connections to the USB port and now have proper connections with the computer. The circuit board also showed no signs of being fried -no burn marks, no blackened components.
In summary --14v on the Sprog II is good for TT. Digitrax DN135 decoders might not be good for JMRI programing through the Sprog II.
I deleted my previous rant. I apologise to those who read it.
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