We seem to be in a difficult situation concerning questions about the repair of electronic gear.
We want to attract a large crowd of hobbyists and experts, and one big motivation why many people come here is because they hope to get advice for their repair efforts. I know from my own experience that I tend to search the internet and especially Q&As most when I'm challenged with a repair project. My experience is that repair questions often tend to sound like beginners' stuff, but at the same time, all of the really good EEs I know are quite enthusiastic when it comes to repairing and maintaining tricky things they keep around as test equipment or they got at flea markets.
I believe that some recently closed repair questions could instead have been edited and improved - and would have continued to be valuable. (For example, instead of closing this question, we could have edited it into something similar to this, which was a part of the closed question from the beginning anyway.) If I ask a beginner's question, I would much rather like to have my question edited into something useful along the guidelines of SE, but my frustration might be big if I would find my question just closed.
When designing circuits as a professional EE, much time is spent on dealing with reliability issues. It's important to know the math of MTBF and worst-case tolerance calculations, but it's equally important to have a gut feeling to know what will likely fail. Nothing can be a better teacher for the possible pitfalls than experience gained from dozens and dozens of gadgets and instruments you have repaired in your life. This is why I enjoy reading other users' repair questions, if they're good ones.
Which brings us to having to find guidelines what good and bad repair questions are: Good is everything that can be helpful if applied out of the box of the certain repair project from which the question originated. Bad is everything where there's no chance it will ever be helpful except during the repair of one specific type of gadget.
Stack Exchange originated with sites that cover software development. While software doesn't have components that fail in random ways (because of things like aging or bond-wire lift-off or counterfeit power MOSFETs sneaked in after two years of flawless series production), much can be learned about electrical engineering when troubleshooting existing circuits and looking for the root causes of these exact types of failure. I therefore would like to encourage users to ask certain types of repair questions. We should work out hints about how to ask great repair questions so they don't get closed.
Sometimes, broken stuff teaches you more than a book or lecture will. "Oh boy, it's broken! Life doesn't get any better than this." This is why I'm strongly in favor of allowing, even encouraging, questions that arise during repair efforts, some rules considered.
A lot can be learned while fixing stuff when you use effort and creativity and don't just randomly swap components. Therefore, we encourage you to ask repair questions whenever you offer us the chance to learn from your project. We enjoy repair questions that are not a one-way-street. For example, a good repair question doesn't necessarily include a brand or model of the device you're trying to fix and focuses on a (sub-)circuit that's of general interest.
Example for a good repair question: I am trying to fix a cassette tape recorder that runs way too fast. By the looks of it, it uses a control loop with an optoelectronic tachometer and a reference. How can I find out where exactly the control circuit is broken? (Ideally followed by block diagrams and oscillograms showing how there's still a signal from the tach, but something weird around the loop's error amplifier.)
Example for a bad repair question: My HP LaserJet IIIp printer shows an "ERROR 52" in the display and won't print. What's broken?
(Both questions may have to do with unconnected pins of a motor driver or servo IC, and in both cases, a motor is caused to spin too fast, uncontrolled, at its maximum speed. But while there is a chance that the good question will cover some details of general interest after a bit of discussion in the comments and will, together with its answers, finally turn into a good source for others who have similar problems, the bad question shows that there is little hope because the author does not pay attention to details like the audible noise from the scanner motor and hasn't even done the least bit of searching the internet for "error 52 laser jet", let alone taken off the cover to look at the circuit board with the part that typically and quite obviously shows signs of having overheated in case of an error 52 in the display.)
I'm sure that bad repair questions will continue to come in and it will still be necessary to close some of them, but I have hope they will be fewer and the overall quality might improve if we provide some good guidelines. Most of all, I hope for some really good repair questions.
I'm looking forward to reading your input and opinions.