You can't fix anything without at least a logic probe and the willingness to learn basic logic electronics. Then you need someone willing to give a lot of advice and/or refer to the more detailed repair logs out there.
For bootlegs, it's not worth paying someone to fix them.
My electronics knowledge wasn't too bad back when I actually had an education, but it was more theoretical than practical. Indeed the qualification that I studied for during my teens was discontinued mid-course for a softer, more rounded approach focusing less on "electronics" as such and more on electrical products. The course I studied for prior to that would probably have been A-level electronics grade stuff at the very least by today's standards.
... but in terms of trying to diagnose which IC on a board populated with IC's is causing the problem, well, that's an impossible task given my tools/knowledge. If we are talking about reading pin-by-pin outputs from IC's on a board and trying to establish whether they are high or low, and whether they ought
to be high or low given the current state; then that's way beyond my current level of knowledge/expertise.
These boards were about £30-40 a go, and at the time that was an OK price to pay, although not a good price to pay for what effectively turned out to be junk.. What sucks is that they were sold as working, and obviously weren't. More fool me, but I was constructing my first supergun and placed too much trust in sellers with good "reputation".
The fact that you seem to be able to repair so many boards is incredibly impressive; especially those with multiple problems.
Thanks for your reply nonetheless.