Electronic distributor kicked the bucket

[SeriesShorty]

After finally getting the electronic distributor (similar to the BritPart and DiscoTech units) installed I barely got two miles down the road before it kicked the bucket and had to be towed home.

History:
24v Ex-MoD, used voltage reducer to drop down to 12v and switched to civilian components. Reducer runs off relay/ignition then sends out 12v to a fuse block. Fuse block powers out through a ballast resister to a non-ballasted coil (I had previously installed the ballast to run a 25d points distributor and hadn't removed it yet since the electronic dizzy was only just installed). Coil + connects to red wire on dizzy and - to black wire.

Tonight I broke out the volt meter to start checking things. The reducer is putting 14.3 to the fuse block. Coil was also putting out 14.3 to the electronic distributor. No juice at all at the electronic module, and of course no juice out of the HT leads.

Any idea on what could have caused the electronic module to burn up so quickly? It ran for only 2 miles, but boy was it a good 2 miles!

Thanks for any ideas before I order another unit and fry it, too. :o

[kevkon]

The two most common reasons for the failure of the electronic distributors or replacement modules are just a poor quality unit or an incorrect hook-up. The latter usually is due to a coil which has the incorrect resistance for the electronic pick up. Check the instructions or specs and then check the primary resistance of the coil. Depending on the unit, you may have to add, remove, or jump a ballast resistor. If everything is compatible, then you probably were just unlucky.

[SafeAirOne]

Presumably it wasn't a Pertronics unit which has a pretty good history and reputation in 2 1/4s. What brand was it and where did you source it?

[SeriesShorty]

I believe someone said it was the same as the BritPart unit. www.simonbbc.com (http://simonbbc.com/automotiveshop/distributors-c-1.html?zenid=4e44038d3500481952600043fe29ab05)

When I ordered it I told them what my coil resistance was and he matched up the unit to what I needed. I guess a bit more research on their end might be my best bet at getting a more acceptable replacement.

edit: My coil is 1.4 ohms primary 9.2 ohms secondary. I couldn't find a ballast resistor locally that was 1.4, so I think I ended up with one that was 1.6 ohms. I'll check with Simonbbc on the resistance of the distributor I got.

[kevkon]

Yeah, I checked that distributor out but wasn't happy with the responses I recieved. I know the Pertronix Ignitor unit ( similar Hall effect pick up) requires the 12+ connected before any ballast resistor.

[Sputnicker]

Sounds like it could be a classic case of infant mortality. In the early days of Lucas electronic ignition, new units were failing at an alarming rate the first time they got hot. Most manufacturers have gotten much better at designing and screening (stressing the parts with temperature and power cycling), but infant mortality is still the most common failure mode for integrated circuits. There is usually some small defect that results in a catastrophic failure as soon as it is stressed.