I have just replaced the wooden dash with the origional binicle on my mark 2. I also placed the tacho in front of the steering wheel. However I am getting electrical interference, ie it pulses with the electrical pump and drops to zero when the lights are on. I sourced the power for the tacho from the terminals behind the speedo. Could that block be faulty. I also tryed a lead direct from the coil but still the same? any ideas please.

Have you connected the 12v wire (+ve) to the 10v terminal on the thing you call the "block" (it's the voltage regulator)?
The 10v terminal is labelled "I" whereas the 12v terminal is "B".

Thank you, I will check that

and check your earth for the tacho

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did I tell you that I won a trophy?

It was a wire earthing within the tacho.
Thank you.
Ian