Hate to break it to you, but I think you'll have to find out when you open it. Not ideal, but not much of any other way about it.
That's how I had to do it. There are a lot of those in there, and as for me, I wound up replacing just one that had leaked pretty bad. Otherwise it's working just fine, and not perfect.
I don't think there are plans of the circuit board going around.
I could be wrong of course.