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Discussion Starter · #1 ·
My original GM '67 blinker tach does not work. A retired electronics guy is looking at it for me but could not find any information that would help him with the repair.

Does anyone reading this have a schematic or other details that might help? (I have the assembly manual, but it only has a wiring diagram for the external wiring.)

Thanks!!

Email: [email protected]
 

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Is the 67 like the 70-72 that have a small ceramic circuit board with parts on it. If so many times it is a bad solder joint on one of the terminals that the wires plug into.
 

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Discussion Starter · #5 ·
There is a small round circuit board at the back end of the tach. Steve, which solder joints are you referring to? Those in the harness outside the tach or the connections at the circuit board in the tach?
 

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The 67 tach has 5 wires.
1-blue, left turn signal.
2-gray, dash lighting.
3-red, switched ignition - power.
4-brown, pulse signal from coil –.
5- black, ground.

The circuit board, that Steve is talking about, inside the tach has a brown colored insulator(?) card attached to the back. The adhesive makes it hard to trouble shoot the board. You can use a solvent to remove the adhesive, but be careful not to remove the resistance material (see the pic). The board has resistors that are applied directly to the ceramic. The board has 5 wires attached, +,-,signal and two wires to the movement. Check for a broken solder joints at any of the wire connections or at any of the components. The circuit board is similar to those used on 68 through 77 Chevelle or Camaro tachs. I think you could adapt the later board to be used on the 67 tach if needed. Here’s a pic.
 

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Discussion Starter · #7 ·
Thanks for the help and the picture. I have passed the information along to the person looking at the tach. Hopefully it will help lead to a fix!
 

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Discussion Starter · #8 ·
I heard back from the fellow looking at the tach. He found the diagram helpful, but needs more information.

On cleaning the surface where the 5 resistors were, he found four were missing and the fifth was disintegrating.

What he needs to repair it is a circuit diagram that includes the resistor values and other detailed information.

Does anyone know where we can find that information? Thanks.
 

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I think it would be easier to adapt a later board to your tach. If you/he can use an accurate mV source to determine the volt/rpm value, which will determine if the later board will work on you tach. If I remember correctly the later tach movements are 5 mV/1000 rpm.

EDIT: Checked my notes, the later tachs are 3 mV/100 rpm

The circuit is a frequency to voltage converter. I don't have the values for the resistors.
 
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