T-Series TF Tach Calibration - DIY?

[Schroeders]

Hello All,

My 1500 TF's tach is reading about 1K RPM too high. Rather than sending the gauge / drive out or replacing the generator pulley, I was hoping someone had pulled the gauge and fussed with the reading via the internals?

I'm hoping for a bandaid in other words..

Thanks!

Jeff

 

[Sarastro]

Well, it's not easy, but if you're comfortable dealing with precision components, it's worth a try. It might just be that the pointer needs to be moved on the pin on which it's mounted, or something simple like that. More complex is that you might need some preload on the spring--so there is actually some reverse torque on it at zero. Some instruments do that, some don't, and I haven't dug into one of these early tachs yet to know.

If you decide to work on it, you will need some way to turn the input shaft and measure it's speed. I have an optical tachometer that I use. I also have a small motor and shaft, with a squared-off end to fit the shaft on the tach. I've used this on Sprite tachs and speedometers, and ones for other MGs.

There may be some way to adjust the magnet position in the cup, but I've never tried that. If you get to the point where that is necessary, I'd send it to the experts. These puppies are not cheap, and you don't want to mess one up.

 

[mikephillips]

Isn't the TF tach like the earlier ones, a chronometric gauge?? Which would have a "clockwork" type internals and not the magnet and cup setup most later gauges were. The chronometric style shouldn't drift from the initial setup since it's all gear driven internally, only requires a cleaning every now and then, unless something actuall breaks and then it should stop working period.

 

[David_DuBois]

The chronometric speedo and tach were dropped in favor of the magnetic units part way through the TD production (October of 1951to be more exact).
Cheers,