TFAS 2 Throttle

Model Railroader Electronics and DCC
1

I’ve been inactive in model railroading for about 20 years. I’ve just started resurrecting some N scale equipment that I bought back then (I was modeling in HO but had moved to a smaller house). Among the equipment I have is a TFAS 2 throttle that I built from an article in MR, and all I have is a very fragile, yellowed copy of the schematic. By experimenting, I’ve figured out the throttle and momentum controls, but there is a second potentiometer on the handheld unit, and two trimmer pots on the circuit board and I have no idea what they do or how to adjust them.

With the momentum control set all the way down, the throttle behaves as I would expect it to, but as soon as I add even a little bit of momentum, the engine sits motionless for a few seconds and then takes off at about 50 MPH, even at a throttle setting that just has it barely moving without the momentum. I suspect that at least part of the issue has to do with the lower current draw for an N scale locomotive vs. an HO scale one.

Does anybody have any information about this throttle and how to set it up properly?

Thanks.

Walt

2

My advice would to be throw it away and purchase an MRC power pack if you want to use DC block control on your layout. Something cobbled together 20 years ago from a do-it-yourself article probably has had components deteriorate to the point of not functioning properly.

3

Walt,

Your throttle may be working fine, as well as the loco. So what’s wrong? The problem may be modern motors. Their design means that older throttles do not have the fine control they need to function properly at low speeds, as their motor sees even the lowest power the throttle can deliver as a mid-range speed.