Repair of Bosch 9 220 066 005 ignition control box.

The 9220066005 ignition control box was used in a popular Bosch electronic ignition conversion kit marketed about 35 years ago that used a Hall effect device in the distributer. Some boxes ending in 4 had the 4 crossed out and a 5 stamped in (see above). The circuit in an actual 9220066004 type box is designed for use with a pick up coil  (Sigma 78-84) rather than a hall effect device but as it uses many of the same components it could be a source of parts as could the Holden Statesman 80-99 box 9220066020.










From looking at the circuit with nothing but the power connected. The current down R2 should turn on T1. The current through T1 should turn on transistor 1007. If  the hall in input 7 is grounded both transistors should turn off. Without a load (the coil) pulling up the output 16 to the + supply the output (3) will only rise to about 7V because of the current down R9 R6.  My guess is that the 2 zeners in series are 75V types. If the output (3) were to get to 300V because of the inductive kick from the coil (5) would reach 150V the zeners would conduct and the 1007 would turn on thus limiting the voltage kick. 1007 is shown as a darlington as this is my best guess from measuring it with a multimeter although the drive of about 300mA seems excessive for a darlington.
I connected a 12V battery + to 15 and - to 31and started measuring voltages with respect to ground. (1) the hall device supply was 12V. (2) was 12V minus the 0.7 diode drop. (3) was 6.7V. (4) was 0V so the 1007 was being turned off. (6) was around 12V so T1 was off when it should be on and was blown up. Replacing it with a BD139 corrected the problem. The coil output (3) now went up to 6.7V when (7) was grounded.  To test it with some load a 21W globe was connected from the coil output to the + supply. The globe turned off an on so the 1007 seemed OK. A second unit had a similar problem.

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