On 3/27/2012 10:48 PM, joost wrote:
It will be difficult to identify any IC. There are some, but all with
unreadable numbers. Thank you for your safety warnings. I wasn't
planning to do anything with the thing switched on. The probes of my
DMM are far to big to have any confidence in not touching the wrong
thing. As it is not worth here having it serviced by a professional, I
think the best shot for me is to take out the two FET's, test them and
replace if they are broken. It is low-cost and if it doesn't fix the
problem I will have to buy a new charger. However taking out the FETs
isn't easy either. It is a doublesided PCB and with only wick and a
sucker it seems impossible to get them off. I will try to cut the legs
and take them out on by one.

Output SCR's go with battery chargers having huge transformers.

Your smart charger probably is a straight forward converter with logic
built around the current and voltage sense to control it.
The good news is that it sounds like the charging path is working.
Bad news is that you probably broke something hooked to the output to sense
voltage and current. Follow the signal path from the + and - output
terminals back to some IC. That's probably what you broke...maybe...
There are lots of ways to do this function. Hard to know what to expect
knowing nothing about it.

The things labeled D are probably diodes.

You need an oscilloscope and an Isolation Transformer,
and someone who knows how to use both, to work on this thing.

Don't underestimate the potential of this thing to hurt you.
You don't have to get electrocuted. All you need to do is go
flying across the room and land on the corner of a desk.

Wear safety glasses. I scratched a cornea in a freak accident
when I came flying out the back of a TV set I was working on.
And I've still got scars where a slip of a probe caused a FET
to explode in my face. There's a lot of energy in a tiny space.
Be respectful.

It's difficult to say without some clues, but
IFF the two fets are on the input side of the transformer,
and the output is 17V, the fets are likely NOT your problem.