My Tachometer wizzes to full hard stop...(ie Max rpm) when I turn on the ignition.... before I start taking everything to bits may I ask if anybody has any thoughts as to why.... ie is the unit or a lose wire ..etc....I guess it could be anything but its curioyus that is goes full over rather than not move...!!!
Remove it from the dash and apply power, if it still moves to max RPM then it is very likely that one of the two driver transistors has failed (permanent switch through). You can replace the old BC148 transistors against the more common BC546C type.
Took out the tacho and with 12 v it goes to full bore so you sat transistors should be changed No problem but how to get inside the thing without wedging the chrome ring off the front ... Or must I do that ????
Unfortunately that is the only way to get in. Use a screwdriver with a bent tip to gently lever off the chrome ring from the back side, with a bit of patience this should leave no scratches or dents.
Could I pick your technical brains please.... I have handy BC 548 and 558 and also some 2N 5401. Which are all similar NPN type Pls can you advise which would be the best to use to replace the old 148s. Thanks
PNPs...whoops. Lucky I asked .... Thanks ...will get the right ones.. ( last time I did this stuff it was with valves ...tubes...). Long time ago...
I also have a question. My tachometer has never been working properly, it’s erratic and bounce around. I don’t have a Dinoplex, the tacho wire is connected directly to the coil. I remember someone suggested adding a 47k ohm resistor, would that help? Thanks
The Veglia electronic tach requires a 12V signal as supplied from the points in a Dinoplex setup, it was not designed to work with a high voltage spike when connected to the coil minus terminal. I've never tried this but you might try a 47K resistor with a 12V Zener wired to ground behind the resistor and then going to the tach. What ignition setup do you have installed?
the original dinoplex is missing, I have the original setup minus the dinoplex. coil directly to points.
Instead of modifying the tach i would recommend to install a MSD 6AL-2 and Blaster 2 coil as a Dinoplex replacement. The 6AL-2 can directly trigger your tach and fits nicely in the luggage compartment space reserved for the original Dinoplex AEC103A. http://www.dinoplex.org/PDF/Wiring_Ferrari_Dino_246_MSD6AL2.pdf
thanks Adrian, I will look into this. how big is a different if I upgrade to MSD from my single coil setup?
It should make a considerable difference in hot and cold starts, as well as in higher revs. The MSD 6A CDI ignitions are similar to the original Dinoplex factory ignition setup. Please also clean the distributor cap from the inside and check your ignition cables, replace them if they are too old ir damaged.
Just say I replaced the old Dynoplex with the MSD 6 and it always starts first time....really pleased with it.....
All of the MSD CDI ignitions should work but not all of these fit into the space for the Dinoplex AEC103A. The best fit is with the 6AL-2 or Streetfire CDI as the enclosure is about the size of a Dinoplex AEC103A.
You are lucky this works as the tacho circuit is designed to switch on a ground/12V signal. Would recommend to add a 12V Zener diode between the resistor and the tach to protect th tach electronics.
I have been running an MSD-6A for 10 years and have been very happy. It is a complete brute force solution to spark. Completely indifferent to the type of spark plugs installed (tried platinum or copper) and at 10km I changed them but were so good that I kept them as spares BTW MSD-6 means "Multiple Spark Disharge" with the "6" meaning the number of sparks per firing at lower RPMs. The "L" provides a rev limiter which is easy to setup should you wish it.
