Tampa 928s

My brothers tach did not work except for just the park lamp. I purchased a used tach and none of the lamps work and the tach is still dead. I am looking at the manual and for the 86 it shows a different pin out, would the 86.5 use the 87 schematic? I am getting a signal to pin 2 verified by a scope, does anyone know what pins go to what on the tach and what I should see?

Tampa 928s

This is what I have:

The signal is good square wave that changes with speed.
12v switched
The only only thing I see is Ignition buzzer to A-16 goes from ground with ignition off to open when started. I am assuming this is grounded when key is in and off to stop buzzer, although buzzer is not sounding. I am wondering if this could be the issue. This is a replacement Tach and yes I got the automatic lamps to work. The 2-Pin connector on the steering column has to be connected.
Question is bad Tach or something else, I hate to send it back and find out its another issue, comments!

With tach looking from front there is 5-posts with nuts I have the following:

Top of Tach

Top post
(12-V Ground goes to lamp on pod)

Middle of Tach
(Left-post Pin-6 12v from fuse 10) (Right post Signal Pin-2 Ctr conn with sq wave)


(Bottom-Post left Pin 16 to Ignition buzzer Bottom-Post right 12 volts to lamp on pod)

ptuomov

I am very interested in this. Can you post a photo? Also, where in the workshop manual did you find the specs for the pin inputs?

Tampa 928s

I used the schematic and traced the pins from the back of the tach. Pins are looking from the front with tach installed in pod.

stolarzj

I just dealt with a dead tach on a 82, it ended up being one of the traces on the board was broken. Did you check if you have continuity from the all the tach nuts to the pins on connector?