Modify an m104 tachometer to work with an om603?
Modify an m104 tachometer to work with an om603?
Here is information about tachometer-adjustment:
All the w124 tachometers I have seen shared the same board layout. Newer versions have a modern style, green board, the older ones have a brown board. But the layout is basically the same. They are all built for different rev signals, but basically the only difference is how many pulses the tachometer gets per crankshaft rotation. Also they are very tolerant to what sort of input signal you feed to it.
There are several resistors and capacitors on the board, you are looking for a small non-electrolytic-style capacitor. In the picture, it is shown in the lower right corner, the green one. This capacitor defines, how much the needle responses to each signal impulse. The higher the capacity, the greater the response. On this board, it is a 4.5nF capacitor for signal input from starter gear sensor (144 pulses per crankshaft rotation). As you can see, I soldered a bigger capacitor parallel to it to increase capacity by 47nF. I did this to modify this tachometer for signal input from generator terminal W.
The dimension of the components on these boards are different from version to version, I recommend to look for the smallest capacitor on the board.
There is also a variable resistor on that board to fine-tune the instrument. With this resistor, you can put an offset to the instument. This is for fine-tuning only.
Grüße
Look at my project-thread for speedometer-informations
Here is information about tachometer-adjustment:
All the w124 tachometers I have seen shared the same board layout. Newer versions have a modern style, green board, the older ones have a brown board. But the layout is basically the same. They are all built for different rev signals, but basically the only difference is how many pulses the tachometer gets per crankshaft rotation. Also they are very tolerant to what sort of input signal you feed to it.
There are several resistors and capacitors on the board, you are looking for a small non-electrolytic-style capacitor. In the picture, it is shown in the lower right corner, the green one. This capacitor defines, how much the needle responses to each signal impulse. The higher the capacity, the greater the response. On this board, it is a 4.5nF capacitor for signal input from starter gear sensor (144 pulses per crankshaft rotation). As you can see, I soldered a bigger capacitor parallel to it to increase capacity by 47nF. I did this to modify this tachometer for signal input from generator terminal W.
The dimension of the components on these boards are different from version to version, I recommend to look for the smallest capacitor on the board.
There is also a variable resistor on that board to fine-tune the instrument. With this resistor, you can put an offset to the instument. This is for fine-tuning only.
Grüße
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