A slightly more expensive solution is to send the A4000 mobo to the Amiga Repair Centre in France. JJ B does an excellent fixed price repair. Not only does he fixed clock ports he also repairs mouse ports and leaky Audio caps. He also has a fix for broken Memory Simms clips.
I'm not that confident with the soldering iron and have used his service to repair a number of battery damaged A4000 mobo's.
Good luck.
TrevorD
