Re: How do Atom Computer Ignition modules work?

[legendre]

Couple of quick updates..

Thanks to Ken for his assistance in obtaining a couple of the BU931T devices he has on-hand.. presently awaiting their arrival.

Also, the second batch of 2SD1071 have arrived, and so far they do not appear to be fakes. Using a 0-15V @ 1.5A variable PSU, I have roughly measured three randomly-chosen devices from the batch of ten, and all indicate hfe in the range of several hundreds (minimum) to several thousands. As expected, gain varies considerably with temperature and collector current.

Interestingly, all of the devices in the batch indicate hfe of 7-22 on my swissknife component tester. This is similar to what I saw from the previous batch of (fake) devices.. I take this to mean one of two things – either the gain (hfe) is so high, that it overflows and confuses the component tester, or the tester is incapable of sourcing sufficient base voltage to turn-on both junctions in the 2SD1071 Darlington pair.

So for the moment, I cannot suggest that anyone use a similar component tester to evaluate a 2SD1071. Use a variable low-voltage PSU and appropriate resistors in the emitter (3-10R) and base (10-20K) circuits, then do the math. I’ve calculated hfe figures in the range of 400 to 9000 at various voltages and currents, within this single batch of ten.