What is inside a Polaris Ficht EMM, computer/logic/ignition/injector driver board

[K447]

Hmmmm . . . can you please tell me what you used to remove the aliphatic polyurethane potting compound? Obviously you start with picking out the bigger chunks, but it looks like you used some sort of board wash.

Mechanical removal only. Toothbrush and dental picks for the final cleaning stages.

There apparently is a special solvent that will actually dissolve the gel, but I do not know what it is called or where to get it.

[HiPeRcO]

Hmmmm . . . can you please tell me what you used to remove the aliphatic polyurethane potting compound?

(Agreed, the potting is polyurethane based, not silicone based)

[bfarnam]

Well its not polyurethane as that is not removable. It is most likely aliphatic polyurethane potting compound. This does not set "hard" and remains a soft "gel" (shore Hardness less than 50 or 70) but is not silicon based as Sylgard is. Silicon based potting compounds do not crystallize or discolor over time and are generally very hard to remove and do not have the heat transfer properties that are desired in the Polaris EMM. They will just trap the heat on the board and heat soak the components.

[MacGyver1981]

Hey guys. Not sure if this is the place to post this? But I’m working on the emm in my 2000 genesis. Q30 looks like it has a diode soldered to it. I’m sure there are people on here the are way better at electronics than I am. I wasn’t sure if the mosfet transistor should be replaced or if this was someone’s way of bolstering it the circuit?

[HiPeRcO]

That is very strange. That diode is connected from drain to source, and if I see the polarity marking correctly it would simply be in parallel to the MOSFET body diode (and installed in the same polarity as the body diode, e.g. Anode to Source, Cathode to Drain). So it wouldn't seem to be doing anything...

Are there other signs of someone being in there and hacking around?

What are the symptoms of your EMM?

[MacGyver1981]

I noticed that c27 was burnt and 28 was cracked. It didn’t idle very well but I found the fpr in the bottom of the tank. Now I have done the repair. The reason for looking was a post I read on here. I haven’t found anything else in there that stands out. But decided to change the capacitors also the dielectrics. So am I correct in thinking I should change the MOSFET ?

[HiPeRcO]

I noticed that c27 was burnt and 28 was cracked.

You mean like this? These capacitors get replaced on every EMM repaired here at Lakeside Tech.

[MacGyver1981]

Pretty close to that. The traces are still good they didn’t burn off.