RPM CIRCUIT UPGRADE (Version 3 and earlier)
![](board_without_transistor.jpg)
Here is shown the board without the BC547 Transistor. If has to be removed carefully because the holes are
too small. It may be needed to drill again the holes.
![](scr_bt149.jpg)
This is the BT149 SCR.
![](board_with_scr.jpg)
Here is shown the board with the SCR soldered.
![](3k3resistor.jpg)
This is the 3K3 resistor.
![](board_place_for_resistor.jpg)
Here is shown where goes the 3K3 resistor (in parallel with the 100K resistor).
![](board_with_resistor.jpg)
3K3 resistor soldered on the board.
![](board_solder_unions.jpg)
2 unions have to be done soldering.
![](board_with_capacitor.jpg)
Here is shown where the 47 nf capacitor is placed (between Anode and Katode of SCR).
![](bnc_connector.jpg)
The original red connector has been replaced by a BNC connector. It has been used a plastic connector to
avoid the electrical noise to go to the display trought the aluminum plate. As the BNC connector is a bit
bigger than the red connector, the hole has to be drilled again.
![](signal_solder.jpg)
Here is shown the soldering between the signal pin on the BNC connector and the original wire from the board.
![](ground_solder.jpg)
Here is shown the additional wire placed from the ground of the BNC connector and the ground of the board.
To the 3K3 resistor.
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