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 Post subject: Re: ECU repair
PostPosted: Tue Jul 24, 2018 9:58 am 
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Location: Bournemouth
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From memory the 10uF on the large board is right next to the transistors that switch the idle control valve. I would therefore suspect it is in as decoupling for these surges, and will mean it is seeing transients of 1 - 2 A, way outside normal rating for a 10u Electrolytic.As above, I will probably be changing to surface mount ceramic instead for future repairs. Back when these ecu's were designed, a 10u ceramic was a large item, now they're down to 0603 and I think even 0402 size (AKA microscope tiddlywinks).

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 Post subject: Re: ECU repair
PostPosted: Tue Nov 27, 2018 8:48 pm 
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For reference I'm now fitting through hole 10uF ceramic - RS 502-0201. Not cheap but being through hole is a better technical solution than a surface mount.

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 Post subject: Re: ECU repair
PostPosted: Wed Sep 30, 2020 12:11 pm 
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Another update to this.



I've now had a total of 3 of the ECU's I previously repaired come back again. 2 of these were early ones I repaired and both have had another capacitor fail. A different capacitor in each case.



I'm now changing policy to changing all electrolytics on any ECU's I work on since it seems others are failing. sadly, the others are larger values so not viable to use ceramics. I'm just using good quality high temperature electrolytics which will hopefully give another 20+ years.



Why they are failing I'm not sure. Electrolytics are fragile in a few ways - High ripple currents, especially high frequency - high temperature and leaving unpowered for long periods of time. The ones which failed previously were used for decoupling without a small ceramic in parallel to take the high frequencies - a recipe for disaster.

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 Post subject: Re: ECU repair
PostPosted: Wed Sep 30, 2020 8:02 pm 
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Joined: Sat Jul 16, 2011 8:13 am
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Location: North East (Cullercoats)
Car Model: ST185 CS/RC
Well thanks 'nibbles', I cannot even remember which car it was that you did the ECU on but I am in contact with both new owners and could pass on your details in case they have problems, if that is ok with you?
I have a 1971 triumph 13/60 convertible now :) ...no electronics

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 Post subject: Re: ECU repair
PostPosted: Thu Oct 01, 2020 1:16 pm 
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Happy to help if needed. This information would also enable local electronic repair places to carry out repairs as well.

If the file sharing works, this is a picture showing locations and values of all electrolytics. Replacements should have voltage rating at least as high as original, and temperature rating at least 105C.

https://drive.google.com/open?id=19C19y ... SfDezjOoDB

Pictures of 2 ecu's with further failed capacitors (different cap. in each case).

https://drive.google.com/open?id=135OOb ... HYg1PAcB_I

https://drive.google.com/open?id=13AuDZ ... CYPYlIasD3

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 Post subject: Re: ECU repair
PostPosted: Thu Oct 01, 2020 4:23 pm 
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Location: North East (Cullercoats)
Car Model: ST185 CS/RC
Cheers mate. I will save that and pass it to anyone who may need it.
Thanks

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 Post subject: Re: ECU repair
PostPosted: Sat Oct 03, 2020 9:17 pm 
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Joined: Wed Jul 13, 2005 12:14 am
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Location: Camberley, Surrey
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That's interesting Chris - I believe the theory in the past was a dubious batch of components, do you think that is still likely or could it be something else?

Cheers for sharing.

Mike

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 Post subject: Re: ECU repair
PostPosted: Sun Oct 04, 2020 11:19 pm 
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I stopped thinking that a while back. Knowing the one on the bottom board was decoupling for the idle solenoid with quite high current ripple I concluded is was ripple, particularly the absence of a ceramic in paralell.

I haven't managed to trace the circuits round the 2 that have failed subsequently. One being only 10V rated would have probably been on a 5V rail, or could have been in a low current scenario in a signal circuit. Either way, probably not such high ripple current. I'm begining to think temperature may be a factor - I've never actually checked how hot it gets, but it is down near blower outlets.

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 Post subject: Re: ECU repair
PostPosted: Mon Oct 05, 2020 8:32 pm 
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Location: Camberley, Surrey
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Probably mostly unrelated but when my Link G4 PNP failed last year I asked about temperature and they said it could have been a factor, the Link has the capacity to monitor its own temperature, when I get the car running again I'll see if I can get some numbers.

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