Bosch number 0280800286
Inside the box is 2 main PCB:s - circuit boards.
1 pcb for the logic cpu,rom.
1 pcb for the powercomponents which the main connector is soldered to.
My goal was to check the soldering in the the box.
The logic pcb was properly soldered but the "power" pcb had about 4 bad soldering joints.
There is also a 3rd pcb ,its a small one with a black plastic cover located standing in the middle of the "power" pcb.
Don´t ever try to remove the small plastic cover,like i did.
Inside there is a small chip which is glued with a little plastic ring around the chip.The chip is connected with microscopic thin leads
which is "in the glue"
When you take of the plastic you move the plastic ring which cuts off the chip leads.
Could this be a copy protection thing ?

Other info for the electronics interested.
Intel/philips 8836v3 cpu + rom
+5 volt 5-pin voltage regulator.
An interinsting thing is the push/pull configuration for controlling the EHA.
The EHA is current limited with 20 Ohm.(2pcs 40 ohm in parallell)
When i get my new box,i will connect 2 leads to the resistor(s) This will make it easier to measure EHA current.
10mA will be 0,2 Volts.

The OVP power to the Jetronic is easily checked by removing the black cover on the Big connector and check 12volts on pin number 1 when the car is turned on.

With modern electronics you could have this function in almost molded in the cable.

Pelle

300E 4M 5speed -89