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Hacking up Honda's ECU
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PostPosted: Tue Jul 05, 2016 5:27 am 
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Location: New Zealand
Hello,

I have a 1550-1500 JDM P30 ECU in my Vtec Mini (b16a2) and vtec stopped working.
I took it off the road a week ago to do some work on it that I had needed to do for a while, and tonight I thought I would have a look in the ECU, as I chipped it ready to pull some ODB1 data out of it for logging.
Anyway, long story short, I can see corrosion on the board around IC13 and IC14.
This ECU was an Auto, so it has all 4 of those IC's, IC13, IC14, IC15 and IC16.
To my understanding, IC15 and IC16 are not required for Manual Vtec, they are for Auto. Is this correct?

Image

I removed IC13 and IC14 as the board under them was shocking. I thought I would then have IC15 and IC16 as spares in case I needed them.

This is what I am looking at.
Coloured arrows indicate what I think should be continuity.

Image

C71, which is next to C72 there, was black. its upper terminal is isolated from the bottom right pin of IC14, and also from that via to its right. That via jumps over to the via tot he left of C70. Those two vias are still continuous, but no longer to the IC14 pin or to C71.
The track going between IC13 and IC14 indicated by another coloured arrow, is high resistance.
And then on IC13, that track indicated there is still continuous, but it doesnt look very healthy.

I basically need some advise please.
What is the best course of action.

I have cleaned it up a bit more that the photo, however that photo is a huge amount cleaner than what it looked like before I started cleaning it up.
I'm tempted to scrape off the solder mask on some of the tracks and put on a little jumper wire to fix the bad connections, but as to what to do about C71, I am not 100% certain. Even C70 doesnt look very happy, none of those 4 do really.
They all seem to be decoupling caps of some kind, to ground, so that makes life a little easier I guess. I could relocate them and solder something direct to the IC13 and IC14 legs if required.

If anyone has suggestions, that would be great.
If anyone has a schematic of this area, that would also be hugely appreciated.
It would be really neat if I could substitute IC15 and IC16 to do the job of IC13 and IC14 by cutting and joining tracks, and leave this bad area of the board alone as much as possible.

Please assist

Thanks


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PostPosted: Tue Jul 05, 2016 7:53 am 
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Ended up just going for it. After removing IC13 and IC14, I removed the 4 caps as I couldnt trust them, especially looking at how C70 was looking.
Removed them and cleaned up the board with isopropyl, and then removed a small part of the solder mask around the bad areas, so I could get a good solder joint.
I was going to run little wires, but ended up doing solder blobs, basically making an external track.
I then desoldered IC15 and IC16 and the 4 caps, and placed them in the 'bad' location.
I then joined all the parts up with solder. C70 was actually isolated from IC14 completely, the track was just gone, along with the feed that went into it. So I did blobs direct from the incoming lines, onto the caps and onto the legs of the IC's.
Not the prettiest, but hopefully will mean things are operational again.

There are a number of areas which are suffering from similar corrosion, which is not good.
This PCB is essentially toast. :(
I really need to find a replacement at some point. Hopefully this one carries on working for a while longer though.

Here is the butchered end result. Think its about as good a result as could be hoped for really, considering the tracks were so corroded.

Image

Needs a clean down again, and then a coating spray to protect it as well as possible I guess.

Cheers


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PostPosted: Tue Jul 05, 2016 6:46 pm 
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Area around the big 220uF 35V cap didnt look too good either, so removed the cap, and wala - the source of the problem.
The cap looks to have leaked, eaten the + terminal completely, and then caused corrosion everywhere in the immediate area.

Image

Image

This is after I cleaned it up a bit. Still more to do, will replace the cap, fix up the +ve PAD, and then reseal it. Hopefully that will solve the issue.
Image


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PostPosted: Wed Jul 06, 2016 12:01 am 
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After I finished cleaning the board up a bit more
Image

All electrolytic caps replaced, some with higher voltage ratings as thats all I had.
220uF is now 50V instead of 35V so its a bit larger, but plenty of room. Some 10V's are not 16V, etc.

Image

Hopefully this is job done. Sprayed on a new coating of lacquer.
Will test it out in a week or so when the car is back together.

Image

Hope this will help someone at some point. Either what NOT to do, or what to do to make a damaged PCB work again... lol. Not pretty I know, but not alot of options. Better than binning it though.


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PostPosted: Wed Aug 03, 2016 4:50 pm 
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Do you know C70 capacitance value?


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PostPosted: Sat Aug 27, 2016 10:41 pm 
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Sorry I dont, no.

Just completing this post - The above mods worked. ECU is fully operational again.


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PostPosted: Tue Aug 30, 2016 6:01 am 
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Hello,
Show me the C70 position on PCB, and I should be able to give you value.


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PostPosted: Tue Aug 30, 2016 6:24 am 
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2nd picture from the top you can see it (C70). Under IC13


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PostPosted: Sat Sep 10, 2016 1:47 pm 
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Image


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PostPosted: Sat Sep 10, 2016 1:55 pm 
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Only board using Sk5050 have this cap, if SK5151 dont have.


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