Recalibrate 911 tach?, 6 cylinder tach reads too low Options

[914ltd]

I know there is lots of talent on this sight. Anyone set up to recalibrate a 911 tach?

I am doing a /6 conversion for my customer and this tach reads low, p/n 911.641.301.01. Both Hollywood and Palo Alto are quoting a long turnaround time.

Thanks Brad

[timothy_nd28]

The old heathkit circuit boards are very similar to this era tachometer. Yes,you can obtain replacement parts from Mouser or Digikey type stores. Some components are no longer available, so I have found proven suitable replacement parts and updated the schematic in an attempt to help others resuscitate their own broken tachometers. Values for each component is listed in the above schematic, just keep in mind that this schematic is strictly for 911 tachometers only.

The 914 tachometer has slight variations, and I have not posted a schematic for it yet. An answer for a future question, yes you can take a 914 tachometer, change out a few parts and make it work as a 6 cylinder. I have yet to try this out because I found some other cheap but slick answer with the sunpro conversion. It killed two birds with one stone by eliminating the tach bounce and also having the ability in different cylinder selections, all the while keeping the 914 tachometer looking stock. However, the sunpro cheap tachometers are being phased out and my instructional thread will only work with this sunpro tach.

I'm working on a new project that uses a air core friction less motor and a custom circuit board that fits into our existing tachometer without monkeying around like my instructional thread. It will have very quick response time with zero bounce and a memory recall feature. It would be nice to cycle the igntion key twice and have the tach point to it's highest rpm after your kid has borrowed your car for the night.

Once this is finished, I will post the schematic and code for all to have.