83 (us spec) 633 ECU

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Richard Sexton - 23 Oct 2007 06:44 GMT

Anybody ever repaired one of these things? Hans and Franz have
figured out mine is fragged, as the car runs with an ECU from
their 5-series sparts car but starts but will die under any load
with my ECU.

They say they've seen this before with a 7 series of similar vintage
and deduced somehow it was the airflow metering circuit.

Absent any bloack burned out parts I'm tempted to go down there,
grab my ECU and resolder every joint.

Anybody played with these ever?

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Richard Sexton | Mercedes stuff: http://mbz.org
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Dean Dark - 23 Oct 2007 11:15 GMT

>Anybody ever repaired one of these things? Hans and Franz have
>figured out mine is fragged, as the car runs with an ECU from
[quoted text clipped - 8 lines]
>
>Anybody played with these ever?

No, but similar vintage control boards are mainly discrete components
and a common failure item is capacitors. If you're doing a home
refurb of the ECU then you should replace all the caps and look for
places where any have puked electrolyte onto the board. Then repair
any tracks that have been damaged by the leaked electrolyte.

This probably isn't a job for your average Joe, but any electronics
repair shop should be able to do it for $100 or so.

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Dan.

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R. Mark Clayton - 23 Oct 2007 11:16 GMT

> Anybody ever repaired one of these things? Hans and Franz have
> figured out mine is fragged, as the car runs with an ECU from
[quoted text clipped - 3 lines]
> They say they've seen this before with a 7 series of similar vintage
> and deduced somehow it was the airflow metering circuit.

Very temperamental part.

> Absent any bloack burned out parts I'm tempted to go down there,
> grab my ECU and resolder every joint.
>
> Anybody played with these ever?

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Scott Dorsey - 23 Oct 2007 14:58 GMT

>Anybody ever repaired one of these things? Hans and Franz have
>figured out mine is fragged, as the car runs with an ECU from
[quoted text clipped - 8 lines]
>
>Anybody played with these ever?

I have worked on the 5-series ECUs from that era, and they are very,
very prone to cold solder joints especially on the connector. Looks
like it might be a wave soldering issue. Occasionally there are also
some capacitor failures too, but a whole lot fewer than you'd expect.
The 125'C rated caps from BCC seem good replacements when you do find
a bad electrolytic, but most of the rail bypasses are mylars. Very
nice design.
--scott

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"C'est un Nagra. C'est suisse, et tres, tres precis."

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Richard Sexton - 23 Oct 2007 16:48 GMT

>>Anybody ever repaired one of these things? Hans and Franz have
>>figured out mine is fragged, as the car runs with an ECU from
[quoted text clipped - 16 lines]
>a bad electrolytic, but most of the rail bypasses are mylars. Very
>nice design.

Thanks Scott. So I'm not out of my mind then that a good first order
approsimation is look for and replace ant sh.t that blowed up and
resolder everything in sight.

Danke.

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