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Anyone know what the resistor color code or value is for the ground side resistor ?  ours is discolored badly and one end solder connection is bad. The board is discolored but might be salvageable, some kind soul has been in here before the potentiometer  is in upside down so no calibration from rear of assembly, (maybe more my first foray).  Anyone have any deep info or a good NOS tach (Yea Right) thanks for playing you guys are great. I have some pics if I can figure out how to attach them definitely a novice on the boards.

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This a PL510 or HL510 (A-10)?


The early 'white needle' PL510 had a 3 wire inductive tach connected in series with the coil, and a later 'orange needle' 4 wire that was wired in parallel. 


Find out what one you have, it might be important to the resistor value.

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So now I have a quandary with my tach:


Orange needle = later style, wired in parallel



three wires = inductive early style wired in series




I guess it's more likely that the 3-wire is wired in series, and the 4-wrie is wired in parallel regardless of needle color.

Too bad for me I was hoping to not have the inductive type - since as I understand it, if the tach fails, the car won't run.😱



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I didn't mention that some early orange needle were inductive. Sorry I never dreamed you would have one.


I can't see how it would fail as the wire simply goes into the tach loops around and comes out. The tach 'senses' the current going through the wire, it's not connected..

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If there is any break in the connection it would stop current flow through the coil. But as I said the tach just senses current flow through the wire it's not connected to it and why it's called an inductor style.

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what we have is a pl510 white needle tach.  I have pictures if someone can tell me how to post them on here, or I could e-mail them if someone were interested.

The resistor in question is open from one side to the other.

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In very general terms you store your picture with a picture hosting site, usually free. When you want to use that picture you go there, copy the picture information bring here and paste it in your post. You may have to practice this, some trial and error till you get what you want.

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Here is a photo of the only resistor I can see  through the back of the housing - without tearing the tach apart. Your photos do not appear to show any resistor on the back surface of the board like this one. Maybe yours has been worked on (or is a different version) and at least the resistor marking will help give you a clue.



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