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By worf
#88190
This first post is more-or-less a placeholder right now. Short Story: I'm hunting an 80-90 mA parasitic current draw that seems to originate with the fan/flap ECU. Or, if the fan/flap ECU is not the problem, then there's a common failure mode with '87+ 928s that results in the fan/flap ECU not going into full standby mode.

I've tested 11 ECUs and 3 different 928s.

Below, are a couple pictures of the rev3 and rev4 boards for Alan to look at, 'cause he's interested. I'll post more when I have a few minutes of spare time.
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By worf
#88192
Rev/4 board:

Image
Last edited by worf on Mon Jun 28, 2021 3:49 pm, edited 2 times in total.
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By worf
#88193
Rev/3 board:
(This unit had been opened before by someone using a dull butter knife. I have no reference for the Rev/3 board so...)

Image
Image
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By Ed Scherer
#88493
I always suspect electrolytic capacitors on aging electronics, especially those that live in hot environments.

I don't know if you still use RL at all, but I started a thread over there in 2017: Keeping old electronics going. Right in the first post, it demonstrates just how bad the problem with electrolytic caps can be. One of my initial examples was a failed APC UPS, about 20 years old at the time. Of the nine electrolytic caps I pulled (with no notable bulging, either), every single one was out of spec. Some, wildly out of spec.

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So... never trust an old electrolytic cap.

Looking at those PCBs you posted photos of, though (I peeked, even though they were apparently only for Alan's eyes only), I see that the electrolytic caps are affixed with copious quantities of snot. Understandable, given the application. But it would make R&R more difficult.

You could do an initial test of the caps in-circuit using an ESR meter and then take it from there based on those initial results.
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