I have an MRC 1500. If my six year olds story is accurate, (and i think it is) he swung it all the way to 100 quickly and the shaft gave way. glued it back in and it was nice and solid however a problem surfaced.
Now when it isturned all the way dow still pumps out 4.0 V. Holding down the brake switch reduces it, but still not past 3.5 V. My first thought was that the spinny thing to which the throttle is attached got miscalibrated (is that possible) or spun but I figured the brake should still take it to 0 V. I cracked it open and looked around for something burnt or touching, but found nothing. I re-removed the shaft and tried turning it HARD with a screwdriver past 0 but hit a hard stop and spun the whole mechanism.
Any ideas on what else to look for and how i might repair it?
I hate to tell you this, but you indeed broke the pot. And it did spin inside.The only fix I know of is to replace the pot. You must have a strong 6 year old in order to do that.
Good Luck By the way in referance to a pot that is a potentiometer…
Yes it is possible to find one at Radio Shack that will work , BUT… you need to know what the value of the broken one such as 1k 10k . If you can see the bottom of the pot they are usually stamped on the bottom indicating what value it is.,and of course the length of the shaft is also important… It would be great to have a schematic. Perhaps giving a call to MRC.could help you. They might even offer to repair it for a fee. I’ve had one for about 30yrs and it still works. I use it at my work bench.
Good luck finding the right value at Radio Shack. And even if you do, the RS potentiometers are in a word, junk. They have a huge dead band off the minimim side and tend to be electrically noisy - not good solid contact, and if it was in an amplifier or somethign liek that you’d hear the scratching as you turn the knob. I made the mistake of making a jump throttle for my Digitrax Zephyr using RS parts because I didn’t feel like waiting for an order from Mouser and that’s exactly what happened - for the first quarter turn of the knob, nothign happened, no motion, then the loco finally started and was somewhat jumpy unlike runnign oen from the Zephyr control which was smooth.
I agree with what you said about the RS junk. I was just trying to give him a avenue. I don’t think they make that transformer any more… I still believe his best bet is to call MRC. they may be able to help him.
If you are thinking about buying a pot make sure you order a linear taper and NOT an audio taper. If the value is 1K you will need a 1/2 watt pot, 1 watt may be better.