I am an electrician with 8 yrs experience of electrical installation work and another 7 years of electronics work and I wouldn't be able to answer your question. You will need some pretty specialist and expensive test equipment in order to find the fault for this. If I were you I would take the plastic casing off the thing to expose the electronics, give it a really good clean, re-solder all the solder work on any of the cirtcuit boards that look like they might be assocciated with the laser and put the lot back together. This will fix a lot of faults. In my experience, a lot of faults are caused by dirt and poor quality soldering in the manufacturing process. The design process is usually good and components dont usually break down. If that doesnt work, you dont have a lot of hope, other than signing up to an electronics repair course at college and buying a bench power supply, an oscilloscope and a good quality, professional multi-meter. If you dont have any electronics thoery knowledge or practical electronics servicing experience then your best bet is to go get a refund and buy another one that works. Sorry, its probably not the answer you want to hear but its the truth.
First thing I said was that with all my experience I wouldnt be able to give you an answer. Its impossible to give electronics fault finding advice over a forum like this. You might have wasted a tenner but this time you got lucky and it worked. Congrats. You must feel good. I get a real buzz out of fixing broken things and usually its not that hard. Its a gamble if you dont have the expensive test equipment and sometimes you fix the fault, sometimes you dont. Well done mate.
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