Hi Rax,
I just thought I would give you some ideas to rule out the trivial solutions and perhaps provide advice for others who have not had much experience tackling the Fluke 5440B before. Your introduction post sounded like you just opened one of these devices for the first time. Sorry about that.
If you suspect that the card slots are dirty, then try the following:
- Use a paintbrush to loosen the dirt, then apply a blower (not compressed air as it has oils)
- Find a stick of the same width of the card
+ I have heard people using erasers, but I have not tried this approach before
+ If a stick is not easy to find, perhaps just fold a piece of paper until it becomes the correct thickness
- Fold some printer paper around it
- Apply a solvent like isopropyl alcohol or a contact cleaner
+ I use a spray bottle to reduce waste and contamination
- Run it in and out of the affected slots until no more dirt can be seen, then keep going for a while just for reassurance
- Make sure to clean every contact on the cards with a Q-tip or paper towel before reinsertion
+ The fibres and hairs that may get caught along the trace corners can be removed with a brush or tweezers
I know that the instrument will not respond or display anything without A11, A17 and A19, which seems to be your problem. I would start there for the slot cleaning. I do not recall if the green light turns on when the cards are pulled. My instrument was really dusty when I first got it, especially on the bottom where the motherboard is mounted. While you are there, there are some shielded cables that you could examine. I think one is for the power button, but I don't remember for sure. Perhaps there is a bad solder joint, or something got torn -- hard to believe, though, given that no one ever wants to go back there.
The green light being on seems odd to me. Maybe there is something to that.
If you have another 5440B that you do not mind opening, I would suggest swapping those cards, including the transformer, to see if you can isolate the problem.
In any case, I would pull every single card from the 5440B to give the mainboard a thorough examination. I know that some people with 5700As have had mainboard burnout traces before. That would be an ugly repair, but it is possible.
Regards.