Repairing potted electronics

[Superflan]

Hi,

Following up the Suzuki GW250 bike that is now mine and it is on it's second ECU failure...

I removed (by cutting corners and prying) the hard plastic casing. It exposed the black putty, which is thick but not hard like plastic, more soft like thick rubber.

I then decided to go where I think coil drivers would be and discovered something. But after googling the markings and riding zero info, out of hope I tried moving the parts... I heard a cracking sound, wondered if it would start the bike ... And it did right away!



I think bad solder joint, since I don't know how to remove the putty properly, I can't observe if the parts are SMD or legs through holes.

 

[supton]

Google

I'd review anything on EEVBlog as perhaps more true than elsewhere. But more than a few links there under google.

I've never tried to unpot something. Good luck. If it's a soft rubber I would probably just attack it with a razor and mechanically remove, bit by bit, then use IPA to clean.

If it's the second ECU do you know if your voltage regulator is ok? I wonder if you have garbage for power. Alternatively, is this an older machine, thus maybe the electrolytics are just getting old?

Those caps in the photo look SMT to me.

 

[Skippy722]

Isopropyl alcohol might help, but you’ll still have to do some digging. Acetone might as well, but may damage other components or the PCB.

As for those components, they look like aluminum electrolytic capacitors.

 

[kc8adu]

start by resoldering the pins on those connectors and the relay at the bottom of the pic.

 

[supton]

start by resoldering the pins on those connectors and the relay at the bottom of the pic.

Good point, solder joints are most likely to break on the connector pins (most flex).

 

[EdwardC]

It might also help to slightly heat the potting to peel it off (or it'll make a bigger mess, depending!).

 

[electroken1]

There are a hundred different potting compounds ranging from rock-hard epoxy with embedded sand to gooey stuff that comes off with a fingernail. Part of my job is "competitive analysis" and I get to dig a lot of the stuff out of competitor's products. In your case I would avoid chemistry and stick with plastic tools and patience.

 

[andyd]

Please post a follow up TIA

 

[Superflan]

I

Please post a follow up TIA

Forgotten to turn on notifications for this thread and then I came back and see all the replies!

Well, I found nothing chemical that will remove the putty.

Tested all the wiring, regrec and alternator, everything is fine except a leak on one of an HT plug wire (when enough water is near the ignition coil, the sparks tends to escape and go to frame instead... bike starts to run on 1 cylinder And I get shot if my hand touches the throttle cable fitting near the handle)

But when fiddling with the board mounting it to the bike, I caused a no-start issue, and it's only when moving the four transistors (deemed to be) that it started again. I think some solder joint or some leg issue on the component. I'd like to replace them but I can't find any spec on the Internet.

 

[andyd]

The plug wires on my Willys Overland do Brasil were shorting when damp. I bought a tube of boot grease and massaged it into the dried out insulation. It did the trick. Just for kicks re-flow the solder holding the legs to the board

 

[Superflan]

I r

The plug wires on my Willys Overland do Brasil were shorting when damp. I bought a tube of boot grease and massaged it into the dried out insulation. It did the trick. Just for kicks re-flow the solder holding the legs to the board

Wow interesting, but at 11.50 each coil I think I will replace both?

 

[kc8adu]

first step is to clear the potting from the solder side around the connector and relay.
then resolder all the pins.
the silver things are capacitors.
not likely to be mechanically intermittent.

 

[Superflan]

first step is to clear the potting from the solder side around the connector and relay.
then resolder all the pins.
the silver things are capacitors.
not likely to be mechanically intermittent.

It's really when I poke around those silver things that I trigger the failure. I tried shaking the 2 connectors around but nothing would make the bike stop... Except slightly poking around the silver components.

 

[kc8adu]

anything is possible.
but the type of leads those caps have makes it unlikely for their solder joints to be broken .
the leads snap off first.
they are likely just supply bypasses and unlikely to stop it dead.
having it in hand for inspection would make it easy for me to find the problem.