# Problem with Revo install in a GP-9



## Joe McGarry (Jan 4, 2008)

I just installed a Revo in a USA GP-9, got power and motors hooked up and got it linked to the receiver. Seems to run normally on test track on my work bench. I ran it back and forth for about 15 minutes and all seemed well. Then I just happened to touch the weight block that the smoke unit regulator transistors are mounted on. It was so hot I couldn't touch it (estimate about 180 F. I thinkl I caused this problem myself. There are two smoke reulators in this loco one attached to the weight block in the from and the other to the block in the rear. To make room for the Revo capacitor board I moved the regulator from the rear weight block and attached to to the front block along with the one already there.

I'm running 19V on the track. have a 3 amp fuse between the track and power supply. The smoke unit switch is in the off position. The shell is off so the smoke units are disconnected.

I just did a quick check and found that there is voltage present in the metal base of these current regulators. I thought those were just to mount them and pass heat to a heat sink Although the weight blocks are inslated (mounted on plastic)

I expect connecting them both to the same metal block is causing some kind of short causing the heating problem. Hoping someone with more experience than myself can confirm this, or otherwise tell me what I did wrong.

Hope I got enough information here for someone to help me out. Thanks in advance for any feedback

Joe McGarry


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## Greg Elmassian (Jan 3, 2008)

Yes, stoppit! 

Weren't they originally on separate weights? 

Greg


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## Joe McGarry (Jan 4, 2008)

Was that Yes, Stoppit ! OR Yes, Stuppid !









Guess I'll see if I can switch 'em back. Seemed like a good idea at the time

Thanks for the quick response Greg.


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## George Schreyer (Jan 16, 2009)

They may not like being bolted to the same chunk of metal. If they haven't changed their design, the heat sinks on the transistors that they use are electrically hot.


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## rmcintir (Apr 24, 2009)

An interesting exercise AFTER you remove one from the metal block would be to measure voltage difference between the metal block and the ground plane on the voltage regulator. If it isn't 0 then that would definitely be the problem.


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## TonyWalsham (Jan 2, 2008)

You could possibly use the same chunk of metal if you fit mica insulators under the tabs and plastic hole bushes *before* you use the screws to hold them to the metal. 
The TO220 size you need might be available at Radio Shack.


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## Trainwreckfilms (Aug 19, 2009)

I decided to take my smoke units out untill someone comes out with BLACK smoke


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## Torby (Jan 2, 2008)

How do you think you *get *black smoke? It's in electronic parts. 

I concur. The weight must not be at ground potential. RS will have little insulators for the back of the regulator and the screw.


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## Greg Elmassian (Jan 3, 2008)

Sorry Joe! was trying to be funny! 

Yeah, I did the same thing, so do NOT feel bad. I was wondering why they put them on separate weights, and first reasoned that it shared the heat better, but then, looked into it and saw hooking them to the same place could be a problem. So you are definitely not the first person! 

So, I was having a little fun with "stoppit!" 

Regards, Greg


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## Bill Swindell (Jan 2, 2008)

The whole problem is that the tab on those regulators are almost always connected to one part of the insides or another. They always need to be electrically but not thermally iinsulated from the mounting surface. When they were mounted on seperate lead weights, they were insulated from each other.

More importantly, why would anyone want to make their diesel smoke and dribble oil all over the body?


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## Greg Elmassian (Jan 3, 2008)

That makes them more realistic! (of course it seems the stuff gets inside too! 

Yes, as several people mentioned, the metal tab is connected electrically to one of the 3 pins, and you should always watch out for this. 

Regards, Greg


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## Joe McGarry (Jan 4, 2008)

Thanks to all for your replies. This site sure is my greatest resource, as I learn this wonderful hobby!

I ended up moving the regulator back to the original block it was mounted on. Drilled a hole for a self tapping screw in the block to re attach it. End of problem. 
Drilling a small hole in lead is great fun, like trying to brill a rubber block. BTW there is voltage present in the base of the regulator. Another lesson learnrd.

Joe Mc


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