[Adrian] has a lot of retrocomputers, so he uses an RGB to HDMI converter to drive modern monitors. In particular, he has a box that uses a programmable logic chip to read various RGB signals and ships them to a Raspberry Pi Zero to drive the HDMI output. Sounds great until, of course, something goes wrong.
A converter that had worked stopped working due to a bad board with the programmable logic chip on it. Unlike the retrocomputers, this board has little tiny surface mount components. A little analysis suggested that some of the chip pins were not accepting inputs.
The Xilinx device has 5V-tolerant inputs and [Adrian] thinks that 5V inputs may have fried the inputs which can happen if there is 5V on the pin and the device isn’t powered up. The plan was to remove the bad chip and replace it with a new one.
As SMD parts go, the Xilinx chip isn’t particularly tiny, but if you are more accustomed to working on 1980s computers, it can be a bit of a challenge. [Adrian] wisely used a lot of flux and hot air to remove the part. We might have covered the adjacent components with Kapton tape to avoid taking off more than we wanted.
Another idea is that if you are sure the part is bad, it is sometimes easier to cut all the leads off, dispose of the chip, and then remove each pin one by one. He got it, though. We might have cleaned the pads before resoldering them, but [Adrian] elected to just add fresh solder and that did work but the excess solder made it harder to place the new chip.
It took a few tries, but persistence is the key. Luckily, the board was high quality and took a lot of heat as well as the part. If you are timid about doing SMD work, you might find [Adrian’s] journey inspirational. It does help that he has a great microscope. In the end, it worked despite some problems with the video capture causing some confusion on colors.
This isn’t really a tutorial on SMD rework, but more of a first-time diary. If you want something more instructional, check out [Bil Herd’s] post. Or, spend an hour with [Moto Geek].
Repairing an HDMI Adapter Doesn’t Go So Well
Source: Manila Flash Report
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