I've just downloaded the manual and can't find any reference to a transit lock, so perhaps the HP 4070 doesn't have one. It's unlikely that that would cause the problem you've described anyway, but I thought it was worth a check anyway. It's not clear from the manual, but it looks like the HP 4070 uses a mains power adapter module. As the scanner is completely dead, there is a good possibility that this is faulty. My daughter recently blew a fuse in here scanner by using the wrong power adapter (it actually had the polarity the wrong way round). It is possible to buy a universal power module, but considering the low price of scanners this may not be economical. The only way to test the power adapter is with a test meter. These aren't expensive but you do need some degree of electrical skill to use one.