MRC Transistorized Control-master V Model Railroad Power Pack Throttle
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They were wonderful, but these days they are only as wonderful as how well the two main driving power transistors, and capacitors held up.
I built my own from the article "Model train control methods:2" pp 71-75 in February 1973 issue of Model Railroader. You could probably use the schematics fig 6A on page 72 to help repair a malfunctioning Controlmaster V.
Thanks, Mark
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Iron Horseman
Well-Known Member
The first mention of the Controlmaster V in Model Railroader magazine was in an advertisement on page 5 of December 1969 issue.
They were wonderful, but these days they are only as wonderful as how well the two main driving power transistors, and capacitors held up.
I built my own from the article "Model train control methods:2" pp 71-75 in February 1973 issue of Model Railroader. You could probably use the schematics fig 6A on page 72 to help repair a malfunctioning Controlmaster V.
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shootingstar57
New Member
I recently purchased a MRC ControlMaster V from ebay. It doesn't work so I'm trying to diagnose and saw your post. However, I have the issue of Model Railroader Feb 1973 and the article is not in this issue. On those pages in MR, it's part of an article on a O scale Westside model Heisler. I will look for the article in other months. If you see this post, perhaps you can check that reference. Anyway, I appreciate the note that at least lets me know there is some information that may be helpful.
Thanks, Mark
Bruette
Well-Known Member
An interesting question! So, I asked Microsoft's Artificial intelligence "Copilot" for a timeline.
Timeline of MRC Power Packs
Early Era (1950s–early 1960s)
- Selenium Rectifier Packs
- Heavy, ran hot, and gave uneven low-speed control.
- Common models: MRC “Golden Throttlepack” and early Control Packs.
- These were the backbone of postwar HO layouts but limited in finesse.
The Transistor Revolution (mid‑1960s–1970s)
- 1964–1966: MRC begins introducing transistorized throttles, replacing bulky rectifiers with solid-state components.
- 1969: First advertisement for the Control-Master V appears in Model Railroader (December issue, page 5).
- Walkaround tethered throttle — a huge innovation.
- Smooth low-speed control, better overload protection.
- Became a favorite for serious hobbyists.
- Other Control-Master models (I–IV) offered different power ratings and features.
Expansion & Refinement (1970s–1980s)
- Tech I & Tech II Series
- Introduced momentum simulation, pulse power for smoother slow-speed running, and more compact designs.
- Tech II became the “standard” pack for many hobbyists through the 1980s.
- Control-Master 20 (1980s)
- A high-power transistorized pack for O and G scale.
- Known for durability and raw output.
Toward Digital (1990s–2000s)
- Tech 4 & Tech 7 Series
- Continued refinement of DC throttles with smoother control, momentum, and braking features.
- Tech 7 (still sold today) is considered the pinnacle of DC packs.
- DCC Era: MRC pivots into Digital Command Control with the Prodigy Advance and later Prodigy Wireless systems.
Today
- Tech 7 remains the go-to for DC layouts.
- Prodigy DCC systems serve modelers who’ve gone digital.
- Vintage units like the Control-Master V are now collector’s items — prized for nostalgia and their role in the transistor revolution.
Snowman
Well-Known Member
You can read the 1969 issue here:
There was a later version I think, and IIRC that article too was by Linn Westcott.* Components were mounted on perfboard, using pins, rather than on a printed circuit board of any kind. First time I had ever used that method, myself.
[*could also have been Keith Gutierrez]
Still have it, and it still works. I used it just a few years ago to power trains on the small layout I built for my nephew. The burglars mostly ignored it, although some of the track needs to be reset because they leaned stuff up against it. Hiding in a corner helped.
Haven't found that article yet.
Peter Thorne did also build a Pacematic Throttle, and you can find that in the December 1977 issue, starting on page 107:
There was a later version I think, and IIRC that article too was by Linn Westcott.* Components were mounted on perfboard, using pins, rather than on a printed circuit board of any kind. First time I had ever used that method, myself.
[*could also have been Keith Gutierrez]
Still have it, and it still works. I used it just a few years ago to power trains on the small layout I built for my nephew. The burglars mostly ignored it, although some of the track needs to be reset because they leaned stuff up against it. Hiding in a corner helped.
Haven't found that article yet.
Peter Thorne did also build a Pacematic Throttle, and you can find that in the December 1977 issue, starting on page 107:
shortwrench
Well-Known Member
Thank you for the info on the throttles. I built the one in the Dec.1977 issue of MRR. It was for a an N scale
layout on a hollow core door that my son and I worked on. It worked very well. I will construct another
throttle for use when working on dc locos. I've been searching for that schematic for quite some time;
all I could remember it was MRR in the 70's.
layout on a hollow core door that my son and I worked on. It worked very well. I will construct another
throttle for use when working on dc locos. I've been searching for that schematic for quite some time;
all I could remember it was MRR in the 70's.
shortwrench
Well-Known Member
Can you post the schematic for the Cooler Crawler?
shortwrench
Well-Known Member
Thanks.
diesel
Weedy Liver
I should really do up a PCB. I'm up to speed, I make several a month. All my N scale playing is analog.
BTW it's 2025, so it would be a good idea to substitute something for the 2N3055 which is very long in the tooth (and pricey). I looked at Digikey and the TIP3055 looks good.
Edit - actually the MJE3055TG looks easier to use, it's a TO-220 and for heat sink Assmann V4330N will probably work.
BTW it's 2025, so it would be a good idea to substitute something for the 2N3055 which is very long in the tooth (and pricey). I looked at Digikey and the TIP3055 looks good.
Edit - actually the MJE3055TG looks easier to use, it's a TO-220 and for heat sink Assmann V4330N will probably work.
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diesel
Weedy Liver
I put together a PCB for the CoolerCrawler. The "guts" are the same, I only made a small change to the speed control circuit because one transistor can now outperform two of them that were in the original design. I'll be able to have it made this week, maybe build and test it in a few.
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