Tic Toc Tac Reading High

[69 SBbyBB]

I just installed a FBO ignition control box with the Pertronix coil. The engine runs great, but the Tic Toc Tac reads 1800 rpm at 875-900 engine speed. The error seems to be proportional. The higher the engine speed, 4000, the tac is over 6000.
Has anyone had this?

 

[pnora]

If it was OK before I would call FBO. You can buy a replacement board and calibrate the tachometer. RTE sells it.