Dave Zucal posted:Yesterday I repaired another TIU with a dead 74ACT244 on Fixed 1. When I tested it with the new chip, I was only getting a signal test of 8 to 9 on my test track. All other channels have a good 10. So I installed another 74ACT244 thinking maybe I got the first one too hot. I'm still only get 8 to 9 at best. The chips were removed using the Quik Chip method and soldered in dragging the iron. No stress was ever applied to the board traces. I also went through the steps to make sure all Quik Chip solder was removed from the pads and the iron. The post are all tight and have the star washer and lock nut installed. This repair was done on a REV I3. I hate to open up a new can of worms here, but what other component is there that can cause a weak signal, up stream or maybe even down stream of the 74ACT244? I really wish a manufacture would make a socket for the ACT244"s that could be soldered to the pads on the board.
The general flow is like:
FPGA to select mux.
Select mux to ACT244 Drivers.
ACT244 drivers to conditioner network.
Conditioner network to transformer.
So check pin 11 and pin 4 on the ACT244 in question. If those are happy 5V square waves move into the conditioning, if they are not, go back and look at the mux. In the conditioner there's about 5-6 discrete transistors in with the passives that may get you. The last thing is the ferrite transformer that does the superposition. That's all there is in there.
