[Jack P.]

Is their a simple way to test a tachometer on the work bench? I have an original 65 dash tach I want to test, Thanks.

[Scott Thelander]

Mr Serio may be able to help you on testing it....

alot of them work but are poor at calibrating and showing correct rpm

I just hook mine up with a known good SUN tach I have and rev up the old 350 chebby and watch em both

Scott ... my junk only revs to 4200

[70GS455]

Originally Posted by Jack P.

Is their a simple way to test a tachometer on the work bench? I have an original 65 dash tach I want to test, Thanks.

No, not unless you have a function generator, set on square wave with the right duty cycle, like this:

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[Geoff]

You can partially test it on the bench, which may be good enough for your purposes, if you have a drill that the speed is known. It helps if you have a spare points dist, not necessarily a Pontiac. I remove the dist gear, leaving just the 1/2" shaft. I fit a short piece of 1/2" rod into the chuck. You can also use a 1/2"drill bit. I use some 1/2" hose as a flexible drive to drive the dist shaft. Hook up the tach & spin the dist. Tach should register double the speed of the drill.

[Ben M.]

Originally Posted by 70GS455

No, not unless you have a function generator, set on square wave with the right duty cycle

Exactly. You can likely even build it and put it in a little box that has a knob to set the output to different RPM values. It's a minor amount of electrical circuits to do it that you used to be able to get at Radio Shack.

[Greg Reid]

Interesting....I thought that I may have had an old Function Generator...but all I found in my old '80s stuff was an BK RF generator and an old scope. I could have sworn that I had a BK generator around. I would love to see a schematic for the hook up?..Just in case I can find it.. I have a serious 'can't see the forest for the trees' situation around here.

[70GS455]

Originally Posted by Ben M.

Exactly. You can likely even build it and put it in a little box that has a knob to set the output to different RPM values. It's a minor amount of electrical circuits to do it that you used to be able to get at Radio Shack.

Much like the box in my picture

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[Ben M.]

Originally Posted by 70GS455

Much like the box in my picture

Exactly. Something like a 741 or a 7414 with a mechanical knob to adjust the resistor could probably be built for less than $15 and make it look nice. It doesn't need ridiculously fast or ns-sharp edges.

[70GS455]

Originally Posted by Ben M.

Exactly. Something like a 741 or a 7414 with a mechanical knob to adjust the resistor could probably be built for less than $15 and make it look nice. It doesn't need ridiculously fast or ns-sharp edges.

I use the LM3524

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