A watch battery won't work. I bought some Duracell copper top equivelent from eBay that works OK.
Back to the original question, there are a few people that advertise in Hemmings to fix these. And some will convert the sender to electronics for about $250. My own experience with a box full of tachs and senders I bought over a couple of years is that 2/3 of them don't work, or work inacurately or meander. I've noticed that even the length and gauge of wire seems to affect their accuracy.
If you want accuracy, I'd get a modern tach.
Also, isn't the EB7A for a V8? You need a transmitter that's 6 cyl, 12V for a 235.
Jim
