In article goldfern-07ED78.00360701052005@redacted.invalid, Dave goldfern@redacted.invalid wrote:
I have a Umax 300Mhz clone and all I get is a grey screen. Once I saw it was starting OS 9.1. More attempts since then only get me a grey screen with no messages, no "Sad Mac" etc. I've tried a couple of batteries I have around, but still the same. Is it time to buy a battery? -or is there something else I could try first?
It's a long shot.... but I remember a friend of mine had a Mac clone that wouldn't start up anymore. He found that not only was there a battery on the motherboard, but there was also a battery in the power supply (hard to believe, but apparently true). He replaced it and it fixed the problem.
Obviously, unplug the power cord if you're going to open the power supply case!
-- jm
In article jm-592425.10241702052005@redacted.invalid, jm jm@redacted.invalid wrote:
Obviously, unplug the power cord if you're going to open the power supply case!
That is NOT sufficient. I really recommend not opening power supply cases unless you are a lot more expert in the subject. If you think that unplugging the power cord is enough to make a power supply safe, then that pretty much proves that you do not have enough expertise to be doing that. I don't mean this in a derogatory way - just as a statement of fact; one can't expect to be an expert in everything.
Power supplies typically have large capacitors that can hold quite substantial energy even when unplugged. People have been seriously injured, perhaps even killed, by fiddling with unplugged power supplies, thinking that this made them safe.
Maybe some particular power supplies are less prone to such problems than others, maybe even including the one in question. I don't know, as I'm not an expert in it either. I've actually build home-brew power supplies in my older hobby days, but I still wouldn't open one today without going to a lot of precautions (generally more trouble than it is worth, so basically I don't). I do at least know enough about it to be aware of the potential problems. I'd say that if you needed this warning, then you shouldn't be doing it.