So in my efforts to fix the Mackie MCU Pro I found out the key card that was inserted into the station was for a different model. It had never dawned on me to even pull it out and check to see if it was a 929 key card. It turned out the damn thing was for the 927 model.

What does that mean? You can’t change the value of the set temperature without the proper card inserted. It is the whole purpose of the card so that users in a manufacturing environment won’t be jacking up or lowering the specified temperatures needed to work on a product.

I ended up bypassing the key care sensors by opening the station up and removing L6 (a LED) and jumping the pads together with a piece of bus wire. Now I can set any temperature within the 929 range without using a key card. Nice.

I’m lucky I have another soldering iron to use while I made the modifications to the HAKKO 929. I have Metcal iron that works very well for soldering smaller components.