Hi there Thanks, I'm just an enthusiastic hobbyist :)
I checked the tube in a dark room and it does glow, very dimly. Also tried a floppy disk and found the machine will boot from it. I've checked the brightness knob and it makes no difference on the picture, the screen remains blank. Another thing, which i'm hoping other plus owners might be able to answer for me. Surely the tube should glow, even without a video input? I've never really read up on how cathode ray tubes work, so dont know what to expect. James On Friday, 25 January 2013 16:34:45 UTC, Doug McNutt wrote: > > At 06:02 -0800 1/22/13, Haemogoblin wrote: > >I`m not a trained electrician or electronics engineer and I've now > reached the limits of my knowledge for fault testing this machine. So was > wondering if there's anyone on here, that might be able to advise me. > > You sound more like an engineer than you think. > > Biongs, hissing as the high voltage drops, brightness turned up. > > I'd bet on, sorry, a blown filament in the picture tube. There has to be a > source of electrons to bang into the screen and they come from a red-hot > piece of tungsten wire coated with an emitter, I think, copper oxide.. > > Looking in the back of the tube, toward the connector, you should see a > glow, A mirror on a stick will help.. Be careful for the 8 or so kilovolt > line heading for the side of the tube. It's not the 25 kV in a modern > color CRT but it's not something you want to learn about. > > The last time I found your symptoms the real problem was a crack in the > picture tube where one of the connector pins goes thru the glass. It > allowed air into the tube and the filament burned out. > > All of those monochrome tubes are the same for any version of a classic > mac. > > -- > > --> From the U S of A, the only socialist country that refuses to admit > it. <-- > -- -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/ --- You received this message because you are subscribed to the Google Groups "Vintage Macs" group. To unsubscribe from this group, send email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
