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Czech Pro 2 controller question

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#1 Casey Scott

Casey Scott

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Posted 25 November 2016 - 09:47 AM

Hi All,

Im trying to find out some information on the Czech Pro2 controller. I have one and im trying to find out the model of the 2 power transistors on the controller. Mine do not have any model numbers on them. I know that they are Darlington Power Transistors, but I dont know the rating.. I think they may be 25A each, but im not sure.

Any help would be appreciated...

Heres a pictures for reference...File_000.jpeg

Casey Scott

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#2 smichslot



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Posted 25 November 2016 - 04:49 PM

Hi Casey,


Well, well.well.

As I have stated a couple of times at this or other forums the power transistors in a Pro-2 are single emitter-followers, NOT Darlington-transistors.

Darlingtons are used in the Pro-3, which is not made by the same guy who made the Pro-2.


I have tried to repair Pro-2 with 2N5886 (which are 25A types) and that seems to be working fine, thank you very much. However, I would probably recommend 2N5686, which are 50A/300W types. There is no reason to try to match the transistors, because at the currents our cars are pulling the internal emitter-resistance of the transistors are almost balancing the currents between the 2 transistors. 


Go for it!



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#3 Dr. Verdo

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Posted 20 November 2018 - 04:00 PM

Hey Casey,


For sure the transistors on your Czech controller are not Darlingtons, the set of resistor values used would not work with Darlingtons.

I have used these Motorola power transistors for many of my DIY built controllers over the years and they are best I've found based on their specs.


Motorola 2N6274, 2N6275 and 2N6277 all have the same specs except for the collector voltages, but all are 100+ volts so that difference does not matter.

I hate that most BJT power transistors based controllers built today hide the transistor identification.


When I worked for Motorola I had a large supply of these transistors and I should have bought more since Motorola sold the transistor division to ON.

Good quality 2N627{4,5,7} are expensive and hard to find now and I'm still fond of the Motorola parts. There are many crappy examples and counterfeit parts.


Message me on FaceBook if you need more details.



Peter Verdo

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