At a recent ebay discount sale I bought a yihua 8508D rework station .
Mine quit working after about the 4th time I used it. The station was working fine up to the point it started to get intermittent and then quit with a puff of smoke coming out the case. I opened it up, and found more than I expected. Pic below
One of the connectors on the power switch was no longer attached, the wire didn't come loose, the whole connector and internals of the switch had pulled out of the casing. I removed the heat shrink on the switch connector expecting to find a wire and connector , instead it was a wire soldered directly to the switch connector, just tacked in place. Normally that isn't a terrible practice but what they did compounded the problem. They used the switch terminal to join several wires together, so you have the end of 2 wires coming off a solder point on a switch, wires not even twisted together just a blob of solder with wires stuck to it and heat shrink over the top.
When they soldered the connections like they did they heated the switch connections up to the point that the switches plastic deformed allowing the internals to pull out.
I had to re-wire the whole thing with a new switch, new connectors on the wires and wires joined before the end connector. Wires should never use the connection point as a junction, it is prohibited in residential wiring for the same reasons , it is dangerous. Put a bunch of wires together and solder them to a single point and you are almost guaranteed to have one that has a poor connection.
Other issues are they bring in the AC wiring using 12AWG wires then heat shrink that to a single wire that is 18AWG and just bundle all that together along with the low voltage wiring and send that out to the part you hold. For a 5A current at least AWG15 is required and yet they wired the unit with lots of the 18-20AWG stuff.
The air pump is another issue. All the air lines were cut too short and have kinks in them that block air flow. It will take me a few hours of work to fix all the issues I found. I'm still debating if the purchase price was worth it or not, was about $65 shipped. If you have one of these you may want to remove the cover and take a look inside.