Author Topic: Reverse engineering the Bosch K-Jet ignition module  (Read 23197 times)

ptashek

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Reverse engineering the Bosch K-Jet ignition module
« on: 10 January 2013, 11:56 AM »
Right, so I have donated my, Bosch 0227100001B, working spare unit from the 350SE to science, mostly due to the irrecoverably damaged casing. As mentioned in another thread, someone took to it with an angle grinder and long-term, that was the end of it. I have given the case a final blow the very same way, just to get at the power transistor.

The unit in itself is nothing special. I have the schematic almost worked out, and most of the components identified bar the diodes and the big TO-3 power transistor. There are five transistors on board:

3x BCY58X - NPN, replaceable by BC337-40
1x BSV15-16K - PNP, replaceable by BD136-16
1x TO-3 packaged power transistor made by Philips and marked "112 00 08 7/32" - I haven't found what it is yet

If anyone has an idea what that power transistor is, please share :)
I plan to make a test PCB and rebuild the thing using new parts, maybe even surface mount.
I'll share the PCB design and schematic once I have them worked out for sure. It'll be some time.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #1 on: 10 January 2013, 07:16 PM »
As far as what I can remember, early SMPS transistors like BU508 and BU208 were the successful transplants.
Apparently, BU426 works best and there was a variant in TO3 case
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ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #2 on: 15 January 2013, 05:44 PM »
Below are links for the schematic (PNG + gEDA format) and a list of parts I have so far identified. This is revision #6, and as far as I can tell it's electrically correct and identical to the original, but none of this has yet been verified in practice. If you find obvious flaws, please share :)

Standard disclaimer: if you decide to build this, you're doing so at your own risk.

Schematic image (last updated: Jan 20, 2013):


CSV parts list
http://s3.amazonaws.com/MB450SE/repairs/w116_im_v5.csv

gEDA schematic
http://s3.amazonaws.com/MB450SE/repairs/w116_im_v5.sch
« Last Edit: 20 January 2013, 12:18 PM by ptashek »
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

TJ 450

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #3 on: 15 January 2013, 11:12 PM »
it's a nice bunch of discrete components there. Thanks for that, I'm sure this will com in handy at some stage.

Tim
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John Hubertz

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #4 on: 16 January 2013, 12:45 PM »
This may seem a silly question to those with technical expertise, but I've always wondered why all of these early electronics couldn't be serviced with one, rather universal unit.

I've noticed that the analysis ports on all variety of later cars seem to "speak" to a single diagnostic tool - surely there is some universality to the inputs/outputs on various ignition modules?

John Hubertz
"When the going gets weird, the weird turn pro."
(Hunter S. Thompson) 

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ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #5 on: 18 January 2013, 09:46 AM »
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #6 on: 19 January 2013, 12:16 AM »
Can you advise what/where pin 31d goes? Is it not pin 3 (shield for pin 7)?

* check that C8 goes between C an B of T5
* pin 31 cannot be earthed (must have been auto connected when drawn)
* is pin 31d (or whatever the correct number) connected to GND?
* What is the chance that pin1 of T3 is earthed (emitter-D5anode-R6-C3-R8-C6 node)?
* 2x R10, no R11 --> please correct the values and names

more to come
« Last Edit: 19 January 2013, 02:38 AM by djenka018 »
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ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #7 on: 19 January 2013, 05:00 AM »
Can you advise what/where pin 31d goes? Is it not pin 3 (shield for pin 7)?

* check that C8 goes between C an B of T5
* pin 31 cannot be earthed (must have been auto connected when drawn)
* is pin 31d (or whatever the correct number) connected to GND?
* What is the chance that pin1 of T3 is earthed (emitter-D5anode-R6-C3-R8-C6 node)?
* 2x R10, no R11 --> please correct the values and names

more to come

Thanks! :)
OK, this is how the module is connected to the entire ignition system:
http://i.stack.imgur.com/KkC5f.jpg

Here's the PCB with tracks overlay:
http://s3.amazonaws.com/MB450SE/repairs/W116_im_full.jpg

Based on that, and the back side of the PCB, both pins 31 and 31d are GND. Pin 31d is common ground for the distributor and is earthed via the module chassis, and 31 is GND as well - at least that's how I understand it looking at the above. C8 does go between C and B of T5, and yes R11 has gone AWOL indeed. Surprisingly enough there is no D2 on the PCB as well.

Pins 15, 16, 31 and TD go to the 4-pin connector. Pins 31d and 7 go to the 2-pin connector.
« Last Edit: 19 January 2013, 05:02 AM by ptashek »
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #8 on: 19 January 2013, 06:39 AM »
and what about:

* What is the chance that pin1 of T3 is earthed (emitter-D5anode-R6-C3-R8-C6 node)?
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djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #9 on: 19 January 2013, 06:47 AM »
.
« Last Edit: 19 January 2013, 06:49 AM by djenka018 »
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ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #10 on: 19 January 2013, 02:11 PM »
I've updated the schematic image, and parts list too. Double checked with PCB, and it looks fine to me.
There is no D2 and no R11 on the PCB, and the resistor near R15, previously marked as R10, is actually R16.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #11 on: 19 January 2013, 06:09 PM »
I got schematic done in functional order but I can see from it that unless T3 is grounded it cannot trigger.

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ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #12 on: 20 January 2013, 11:18 AM »
I got schematic done in functional order but I can see from it that unless T3 is grounded it cannot trigger.



I think I've been looking at the PCB so much, that I've stopped seeing things the way they are  :o
You are totally right. The emitter (pin 1) of T3 is grounded. I've messed up this fragment on the schematic.

The connection goes like this: R8-C3-R6-C5-T3(1)-GND, and R13-T3(3)-ZD3-R14
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

ptashek

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #13 on: 04 July 2015, 10:22 AM »
djenka018, would you happen to still have a hi-res version of your drawing handy?
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

djenka018

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Re: Reverse engineering the Bosch K-Jet ignition module
« Reply #14 on: 04 July 2015, 06:52 PM »
http://gallery.w116.org/dl/42257-1/w116_im_v_DJ.ps

I do have a .sch somewhere (gEDA) but that will take forever to find.
« Last Edit: 04 July 2015, 07:18 PM by djenka018 »
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