I have a MRC Tech II 2500 that I have been using for a while now, but recently, whenever I start out, it does not apply any power to the track, until I go past "35" and then it gives it full power, even if it is not at full power. I disconnected the track and it still did it. As far as I know, nothing happened to it that would make it do this. Please help!
Does it do the same if the momentum switch is on, or off?
First guess from an electronic pont of view is a capacitor has gone bad. I don't know how much I'd bother attempting to repair this though, you need security screwdriver bits to even open it, and there is no published schamtic to guide any troubleshooting, so you'd be pretty much on your own tracing out the circuit and testing components.
You can pick up the newer Tech IV series used for fairly low prices, as an alternative to spending the money on a brand new current model.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Yes, it does it with the momentum, though it does "warm up" to the speed just like it did before. I will probably just replace it, thank you.
I think you need to replace it.
.
The Tech II 2500 has a Pulse Width Modulated signal for speed control. It was one of the first to use this. It sounds like the switching device for the PWM signal generator has failed.
Sorry, these things happen. That is why I have stockpiled so many out of production power packs from the 1980s and 1990s.
-Kevin
Living the dream.
The older they get, the more likely they will be dead the moment you plug them in, as the electrolytic capacitors dry up with age and disuse. This is not a problem just with really ancient stuff (like tube radios) or from that brief era of the counterfeit capacitors when even a well-known brand name was no guarantee you didn;t have a cheap junk part. Even 70's and 80's era aluminum electrolytics eventually fail, more likely in stuff that just sits on a shelf and never gets powered on.
rrinkerEven 70's and 80's era aluminum electrolytics eventually fail, more likely in stuff that just sits on a shelf and never gets powered on.
I hope not. I have many Troller power packs that never leave the boxes.
For my benchwork test layout I pulled out a Transpak 2.5 that had never been out of the box. It worked perfectly.
I really need them not to be dying on me! I need 20-25 years of service out of these things. Now I have something else to worry and fret about.
Well, as long as you can get inside, they are fixable. The capacitors are about the only thing where this can happen, the transistors don't just fail from sitting there. Maybe the potentiometer gets oxidized and speed control won't be smooth, but a little shot of contact cleaner usually fixes that up. Which reminds me, the volume control on the radio in my truck is having this problem and I need to fix it.
Most transistor throttles shouldn;t fry other parts if a cap goes bad, it's not like an antique radio where if you plug it in and there are bad caps, you can fry a whole lot more things. So if they work out of the box - great. If they have some issues (the biggest cap in the circuit is probably the momentum cap, for those models that have momentum), AND you can get inside the case, it's not too difficult (or even costly) to fix the bad component(s). Even high quality name brand capacitors of the sort used in a transistor throttle aren't expensive, so if you REALLY like those older models, you can keep them going pretty much indefinitely.
I'll admit spending a lot of time in the hobby shop drooling at the MRC Controlmaster XI - adjustable momentum, adjustable pulse width and duration, multi position brake, those big meters... I think they were over $100 and this was the early 70's, so one was definitely never coming home with me. Now working ones sell for like $25 on ebay. I actually have a surplus of DC power supplies to test locos before installing ecoders, so I really have no need to get one but... actually, it will probably be one of those cases of "it looked so awesome back in the day, but in reality, it's not so great". The thing is, what my 7 or 8 year old self didn;t know back then was how all that worked - now I do and with a relatively small effort I could probably build my own that does all that could and more - if I needed it. If I wasn't already using DCC, I might be designing my own DC walkaround system at this point.
rrinkerI'll admit spending a lot of time in the hobby shop drooling at the MRC Controlmaster XI
I know what you mean.
I love my Control Master XI!
SeeYou190 I think you need to replace it. . The Tech II 2500 has a Pulse Width Modulated signal for speed control. It was one of the first to use this. It sounds like the switching device for the PWM signal generator has failed. . Sorry, these things happen. That is why I have stockpiled so many out of production power packs from the 1980s and 1990s. . -Kevin .
Unlike my reaction to the resurrection of threads from years past, Steve can add some useful information.
For those of us with less ability to identify and order replacement parts, could you list part numbers and where you were able to purchase them. Some photos would be great too.
The OP Original Poster hasn't posted in a couple years and Randy was lost to Covid. That said, I'll bet a lot of us still have the 2500.
Henry
COB Potomac & Northern
Shenandoah Valley