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Walt Fricke's Avatar
 
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What did you do to rebuild a tach? Did you just determine the nominal values of the resistors and capacitors, and replace them with new ones? 10% values adequate?
Old 09-10-2014, 01:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
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Bob Ashlock makes TACH-ADAPT which works very well. He is a fellow Pelican and is great to work with. His email is ratech@pacbell.net. He repairs and refurbs cdi boxes too.
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Old 09-10-2014, 04:35 AM
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Originally Posted by Walt Fricke View Post
What did you do to rebuild a tach? Did you just determine the nominal values of the resistors and capacitors, and replace them with new ones? 10% values adequate?
Walt. I wish I were that handy. My method was to pull out a credit card.
Old 09-10-2014, 04:45 AM
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Originally Posted by Walt Fricke View Post
What did you do to rebuild a tach? Did you just determine the nominal values of the resistors and capacitors, and replace them with new ones? 10% values adequate?
The color bands on the resistor tells you what value it has.
Remember we used sheets, but now you can dowload a calculator :-)

Resistor Color Code Calculator | Micro Digital
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Old 09-10-2014, 05:02 AM
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Originally Posted by Trackrash View Post
There is an older thread that explains the tach compatibilities. The tachs from 69 to sometime in 1970 used a factory "adapter", I forget exactly what it was called, and aren't computable with any other cars.

That said, your tach does not look to be original. Only way to know if it will work is to try it.

There is a tach adapter that is supposed to work for this.
Tachometer Compatibility Chart
Old 09-10-2014, 06:45 AM
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Originally Posted by Walt Fricke View Post
What did you do to rebuild a tach? Did you just determine the nominal values of the resistors and capacitors, and replace them with new ones? 10% values adequate?
The resistors were the one thing I didn't replace. They all looked fine, yet still, I de-soldered each (one leg) and check for proper resistance. The Cap's all held some electrons, but with my crude electronics tools, I couldn't very well gauge the capacitance values. (I found new versions of those) The tach has one diode. (easily tested) and then there is that little black 8-legged IC chip. That was my problem. I replaced that and my tach finally came back. -yay! And, as I said earlier, I noticed that with the replaced caps, the tach was much more stable on rough idle.

I do have a bunch of extra caps, and diodes if your interested. (it's hard to buy just one of any of these components - some are a bit unique)
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Old 09-10-2014, 04:43 PM
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What's the 8 pin DIP chip? If you got a new one, the old one must have had identifying numbers on it. Just routinely curious, as my tachs work, and removing and reinstalling bezels is not my idea of fun.

All sounds pretty do-able, if one wants to try and has a need.
Old 09-11-2014, 01:30 PM
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Yeah, it's a pulse shaper chip. SAK215 IIRC ..maybe SAK219 --it does say on the chip.
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Old 09-13-2014, 02:06 PM
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