# Revolution into QSI Magnum socket?



## pimanjc (Jan 2, 2008)

Is it possible to install and operate the Revolution with it plugged into the QSI Magnum PNP adaptor? I have an LGB Genesis that has a QSI and custom rewired lighting. The person that wants to buy it wants to be able to install a PNP Revo into the Magnum after the QSI board and receiver are removed.

Jim Carter


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## Greg Elmassian (Jan 3, 2008)

Should be fine... the only question might be lighting, what lighting modifications did you make? 

(nice to see you posting JC) 

Greg


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## pimanjc (Jan 2, 2008)

The lighting modifications are extensive. The change is for the LGB Genesis that I previously did two threads on about rewireing the lighting to make it more prototypical after a board burnt out. 
JimC


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## Greg Elmassian (Jan 3, 2008)

As long as the lighting is set to handle full voltage of the system, should be no problem. No one has really figured out what the extra diodes are in the non-PNP Aristo adapter, this is why I asked. No one else that uses the Aristo socket needs them. 

Greg


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## Paul Norton (Jan 8, 2008)

To expand on what Greg said. Unlike the 75 MHz receiver, the Revolution receiver does not provide power to the lights, although it does control the grounds (HD1 and HD2) for the headlights. Full power comes directly from the track or battery pack. The diodes in the adapter board or (non) Plug and Play Board ensure the power to the blue lead or HD COM terminal is always positive no matter which way the track or battery pack is hooked up.



While many people are aware that a resistor is required to drop the voltage to incandescent bulb lighting circuits and limit the current to LED lighting circuits, some are not aware that the proper wattage of the resistor is important. As an example, one USAT GP-9 lighting board can draw 245 ma, but only requires 3 volts to run it. If you use a lithium-ion battery pack, the resistor would have to drop (25.5 v – 3 v) 22.5 volts and would have (.245 ma x 22.5 v) 5.5 watts of power to dissipate as heat. That is why the manufacturers use voltage regulators attached to metal (the weights in most USAT diesels) instead of resistors.

Unfortunately in some USAT diesels the voltage regulators that provide power to the lights are incompatible with the PWC output of the Revolution receiver. But as noted above, connecting the light boards to the adapter or (non) Plug and Play Board with dropping resistors also has it problems.

Following George Schreyer’s advice, I realized it was easier to build my own LED lighting boards that modify the USAT ones.



The headlight LEDs are wired in series with a 1K resistor in their own circuit, as are the number board LEDs. 



Each resistor now has to drop (25.5 v – 7 v) 18.5 volts, but there is only 18.5 ma in the circuit to handle. Each has to dissipate (18.5 v x 0.0185 ma) 0.34 watts of power as heat. I use 1/2 watt resistors and have not had a failure or blown LED yet.

Both my GP-9s have on-board battery power, radio control, and sound. But I usually run them as a set and wanted to have individual control over each set of headlights. That would allow me to leave the headlight of the lead unit on and turn all the other headlights in both units off. As the headlight circuits only draw 18.5 ma, I was able to hook up the ground for each set of headlights to a Revolution trigger wire instead of HD1 or HD2. They functioned flawlessly without any electrical problems.

Unfortunately not having directional headlights proved to be a nuisance when the locomotives were assigned to engineers not familiar with the Revolution throttle and my assignment of trigger keys. Here Roger Caiazza of the Finger Lakes Live Steamers looks a bit puzzled while operating one of the units during this year’s American Invasion of Ottawa.



During our railway operations the direction arrows on the screen do not always indicate the direction of travel, so we rely on the LED headlights to indicate which direction the locomotive is going to move. The LED headlights come on full bright at 1% power long before the locomotive moves. Without directional headlights, this can cause some confusion.



The previous suggestion (which I believe was made by Greg years ago) to replace the arrows with FWD and REV has been repeated in the A-C Forums along with other ideas to improve the operation of the Revolution throttle. The one that will be most appreciated by our group will be the capability to lock the cab number of the locomotive being operated to prevent runaways. In our operations this is the most frequent operator error.


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## LogSkidder01 (Jul 30, 2009)

Jim, 
The QSI Magnum boards are simple adapters with no active components. They just provide a convenient mechanism for mounting and wiring decoders. As long as the buyer is powering the tracks from a stable, relatively clean DC source or batteries, he will have not problem plugging in an AC Revolution. I have swapped several QSI and Revolution decoders around. 

Greg, 
The diodes on the AC CRE57077 board provide for installation of directional lighting without the need to use the I/O cable and program the transmitter. Although this is old school, I have had to use these outputs to power some headlights which draw more than the wimpy currents provided by the Revolution drivers. 

Ken


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## Greg Elmassian (Jan 3, 2008)

Thanks for the info on the board Paul & Ken... never had that board in my hands, so did not know the diodes were wired to the track pickups. Well, even on DCC that will work in most cases, but I would probably remove the diodes if I was using it on DCC, just to be safe. You could possibly get a weird voltage "loop" since most DCC decoders supply the positive voltage themselves. Wonder why Aristo did not do like everyone else and put the positive voltage there... 

ahh! It's because the Revo does not have a full wave bridge on the input! (all DCC decoders do because DCC is basically AC)... 

Learn something new every day... 

Greg


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## pimanjc (Jan 2, 2008)

In the Genesis I am talking about, each Led light has its own resistor in line.
JimC.


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