MRC Controlmaster V & Throttlepack 500 has no variable throttle, only full power

[Transmissionjimmy]

I bought a Controlmaster V to use as a variable bench power supply.  I have the output hooked to a Mabuchi RS380 motor to ensure it is under load, and the throttle is just wide open. Someone has already replaced the potentiometer, but it obviously didn't work for them. Is it possible one of the transistors have gone bad? I read a post in a forum explaining that reversing a train on a switching track could cause a direct short if the train sat too long on that section. Is this what would burn up a transistor?

Also, there are no markings on the transistors, how do I tell what kind they are?

I bought another MRC power pack, a Throttlepack 500, & it is the same way, full throttle no matter where the knob is turned. I did notice there is a diode that is burned up. I have another pack just like it that works fine but the diode is fine.

 

Please help! 

[rrinker]

 Two possible problems. Yes, a transistor burned up  however the Throttlepack 500 is not a transistor pack so not the case there. More likely - those packs were desnged for HO loads at the time they were made. Modern motor have moch lower current draws and are pretty much incontrollable with a rheostat pack. If you look around you will  see that there was a Throttlepack 500 and a 500N, the N for N scale - because the low power of the N scale motors was uncontrollable with an HO rheostat, they would just take off at full speed after just cracking the throttle.

 The transistorized power pack has done away with the HO scale vs N scale, a transistor power apck will work for either. It sounds liek that Controlmaster V has a blown transistor.

 Hopefully you are gettign these cheap, as you could just buy a Railpower 1300 which are pretty inexpensive.

      --Randy

[Old Train Buff]

My father bought a Controlmaster V years ago. It never worked. When I got it I started trouble shooting it and found loose connections and diodes (2 of them) put in backwards. This may be your problem.

Good luck on getting it running! Al