Hello all,
I have an SE/30 that's a bit sad right now. First the good. Logic board boots (in another machine), 5v, 12v disk and sweep rails are OK. Nothing has been recapped yet, but the core stuff seems stable enough to at least get a bong (well, logic board isn't bonging, but I'll deal with that later).
My issue appears to be with the flyback. The symptoms I'm seeing are components on the neckboard, R1 particularly are getting very hot very quickly when powered on. There is a little life on the screen when powered on, but nothing like a coherent picture and very dim. The orange wire to the neckboard, which should be 30 volts, is reading 120v - just a little high - at least with the neckboard detached from the tube. I'll double check, but at least on a functioning unit it seems to regulate to 30v when detached and functioning properly.
Looking at the analog board schematic, the 30v rail seems to be derived directly from the flyback with only CR5 in the way, so my assumption is either the flyback is bad or the regulation of the flyback is bad. I've not checked the grid voltages, but I assume they're badly off too. Not really wanting to plug it back in to find out though, and I actually don't have a reference for what they should be.
I'll be ordering replacement components for the the various diodes, regulators and power transistors around the flyback soon, but just checking in to see if anyone else has seen this kind of fault before where it *wasn't* a dead flyback transformer.
Cheers!
I have an SE/30 that's a bit sad right now. First the good. Logic board boots (in another machine), 5v, 12v disk and sweep rails are OK. Nothing has been recapped yet, but the core stuff seems stable enough to at least get a bong (well, logic board isn't bonging, but I'll deal with that later).
My issue appears to be with the flyback. The symptoms I'm seeing are components on the neckboard, R1 particularly are getting very hot very quickly when powered on. There is a little life on the screen when powered on, but nothing like a coherent picture and very dim. The orange wire to the neckboard, which should be 30 volts, is reading 120v - just a little high - at least with the neckboard detached from the tube. I'll double check, but at least on a functioning unit it seems to regulate to 30v when detached and functioning properly.
Looking at the analog board schematic, the 30v rail seems to be derived directly from the flyback with only CR5 in the way, so my assumption is either the flyback is bad or the regulation of the flyback is bad. I've not checked the grid voltages, but I assume they're badly off too. Not really wanting to plug it back in to find out though, and I actually don't have a reference for what they should be.
I'll be ordering replacement components for the the various diodes, regulators and power transistors around the flyback soon, but just checking in to see if anyone else has seen this kind of fault before where it *wasn't* a dead flyback transformer.
Cheers!
