Audi A4 AFN Bj97 springt nicht mehr an -> MSG kaputt ? | Posts 32+

"If it weren't for the standard Siemens C166 chip, which has datasheets with connection labels available, I would never have figured it out. Because I don't recognize any of the other ICs. They all have Bosch part numbers, and there's practically no information or documentation available for those."
At least that way, you have a well-known IC as a starting point for further measurements.

Following the reset line, starting from C166 (/RSTIN), connect the following components:
- C166 (_Reset_IN = Pin 27)
- SCL4410V4 (Pin 44)
- B30279 = Philips CC212V2 (Pin 11)
- A pad for the large, unpopulated PLCC footprint.
- a pin of the TO220-5 package (the only TO220-5 on the board; after removing the heatsink clip, you can still see a Bosch number [which I've forgotten again] and a Siemens label).

Durch Messung des Spannungsabfalls auf der Reset-Leitung komm ich drauf, dass der TO220-5 der Resettreiber sein muss. Das ist ein 5V Spannungsregler (nach meinen Messungen der einzige 5V-Regler auf der Platine). Ich erkenne dort 12V (U_IN), 0V (GND), 5V (U_Out), den Reset-Ausgang und einen 5. Anschluss der an einem 100 nF Kondensator liegt. Damit wird die Resetdauer eingestellt (100 nF->25ms lt. Datenblätter ähnlicher Siemens Spannungsregler). Allerdings waren die Spannungspegel dort recht seltsam und unstabil. DBy applying an external voltage via a potentiometer to the DelayAdjust pin, the reset function sometimes became inactive, and activity appeared in the circuit (PWM, bus accesses, etc.).
Since the 5V supply is stable, I assumed that only the reset circuit was faulty. So, I left that part in place and disconnected the reset output from the rest of the circuit. Now, it's being driven by an MCP130 reset IC (SOT23-3 package, 4.5V, 350 ms). The reset duration is a bit longer than ideal, but I just happened to have that part on hand.

Regarding the voltage regulator: I don't know exactly which type is installed there; I simply searched for Siemens U-regulators in the same housing. That way, you can find parts that might have similar specifications (TLE 4260 / TLE 4265).


Andi.

Rekord81 wrote:

Ich habe gestern nochmal das MSG intensiv durchgemessen und bin letztendlich darauf gekommen, dass der Reset-Generator defekt ist, der im 5V Spannungsregler integriert ist. Der Reset war dauernd aktiv ! Die Reset-Leitung habe ich dann von der übrigen Schaltung abgetrennt und diese dann über einen separaten Reset-IC versorgt.

Wow!

I also have deep respect for you for finding the error. To my knowledge, this is the first MSG in this forum that has died without external interference. It's definitely the first one in the DS forum to die without external interference and then be repaired by a private individual, including a detailed description of the error.

Also, I'm also sorry for trying to distract you from the MSG so often.

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It refers to a sudden and strong gust of wind.

guste100 wrote:

100% jedenfalls das erste im DS Forum, welches ohne Fremdeinwirkung gestorben ist und danach von einer Privatperson repariert wurde inkl detaillierter Fehlerbeschreibung.

@ Andi: Now that you've done such a great job troubleshooting, wouldn't it be good to stay active in this forum as a "StG therapist"? *gg*

Quote:

und danach von einer Privatperson repariert wurde inkl detaillierter Fehlerbeschreibung.

Privatperson stimmt nicht ganz. Ich programmiere beruflich+privat (u.a.) MC-Steuerungen, etwas Elektronik mache ich da auch. Allerdings nix im Automobilbereich, entsprechend gering sind da meine Detailkenntnisse, ich muss mir da alles mühsam erarbeiten. Und eine 4-Lagige MSG Platine ohne Schaltpläne und Datenblätter durchzupiepsen ist für mich auch kein Vergnügen. Ich machs trotzdem, da solche Steuergeräte, die für 1300 Euro von Halsabschneidern verkauft werden, aber einen Materialwert von max. 80 Euro haben, sich oft für ein paar Euro (hier warens 67 Cent +MWSt.) reparieren lassen. AbThat's the same problem with every manufacturer.

Quote:

@ Andi: Wouldn't you like to stay present in this forum as a "StG" therapist (after the excellent troubleshooting)? *gg*

"Thank you, but I'm fully booked until 2025. All things considered, I probably spent a good three full days dealing with this problem (including searching for replacement parts at local junkyards). That's usually time I can't afford to spend. Privately, I only repair things that are needed in my household or that relatives bring me. Right now, I have a TV, a stereo system, a dishwasher, a garden tiller, brake discs for my car, and a few other urgent items waiting to be fixed."

Best regards, Andi.