Diesel tachometer

Hi all: My tach stopped working the other day and I am looking for information on how to troubleshoot it. My rig is a 1991 Gulfstream and I have the 5.9 cummins. The tach uses a mag pickup. I can read about 2Khz at the back of the tach at idle and this increases to about 8Khz at full throttle. I also have the required 12V for instrument power there too. This ratio seems about right to me but would like to confirm this with someone that has more experience. Assuming this is OK then can anyone recommend a good source for a new tachometer. I have not had much luck finding any by the way of the internet.
Thanks for any and all help, Roger.
Diesel tachometer

So what does the transducer pick up off of? Also what is the normal idle speed?
The above will determine the frequency sent to the tack. It so far looks like its picking up on a flywheel ring gear. ????
Problem could be an electrolitic capacitor in the tack, they seem to be the first thing to cause a problem in electronics.
Diesel tachometer

Hi icrman: my normal idle was about 600 rpm and my governed speed was about 2600 rpm. The pickup is located over the flywheel so it may be counting the teeth, I have not pulled it out and looked down the hole to be sure. This tach is a sealed unit and it appears it will only come apart by prying off the face. I would like to be sure I have the right inputs before I take on tearing into the tach, but when I do the math it seems to matchup correctly assuming there are 190 teeth(the lable on the tach lists either 190 or 80 teeth as input choices). Do you know of a good suppier for a new tach, assuming I am unsuccessful at reviving this one?
Thank you for the response, Roger.
Diesel tachometer

Before I would bust up for a new tach, I think I would take a look at the magnetic pick up. It may just need a good cleaning, :)