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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Mag 986FS CRT shimmering picture - schematic?
Anyone happen to have a schematic handy for a Mag 986FS / 986N 19" CRT monitor? (Probably also rebranded by Gateway at one of theirs, although I know their EV900 is a different animal). I was given one the other day where the picture seems to shimmer, at least in part dependent on changes in the screen contents. I can trace out the schematic for the PSU section and go from there if I have to, but having a genuine schematic would be a lot nicer to have! :-) (I've got a 19" CRT on one machine which has a weak tube, so this would be a nice replacement if I can get it running) cheers Jules |
#2
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Mag 986FS CRT shimmering picture - schematic?
Jules Richardson wrote in
: Anyone happen to have a schematic handy for a Mag 986FS / 986N 19" CRT monitor? (Probably also rebranded by Gateway at one of theirs, although I know their EV900 is a different animal). I was given one the other day where the picture seems to shimmer, at least in part dependent on changes in the screen contents. I can trace out the schematic for the PSU section and go from there if I have to, but having a genuine schematic would be a lot nicer to have! :-) (I've got a 19" CRT on one machine which has a weak tube, so this would be a nice replacement if I can get it running) cheers Jules Sounds like a weak powersupply, and/or High voltage supply. Check for bad components around there. |
#3
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Mag 986FS CRT shimmering picture - schematic?
Jules Richardson wrote:
Anyone happen to have a schematic handy for a Mag 986FS / 986N 19" CRT monitor? (Probably also rebranded by Gateway at one of theirs, although I know their EV900 is a different animal). I was given one the other day where the picture seems to shimmer, at least in part dependent on changes in the screen contents. I can trace out the schematic for the PSU section and go from there if I have to, but having a genuine schematic would be a lot nicer to have! :-) (I've got a 19" CRT on one machine which has a weak tube, so this would be a nice replacement if I can get it running) cheers Jules Open it and look for bad caps by the power supply. That's all I've ever had to replace on a Mag. |
#4
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Mag 986FS CRT shimmering picture - schematic?
"Cydrome Leader" wrote in message ... Jules Richardson wrote: Anyone happen to have a schematic handy for a Mag 986FS / 986N 19" CRT monitor? (Probably also rebranded by Gateway at one of theirs, although I know their EV900 is a different animal). I was given one the other day where the picture seems to shimmer, at least in part dependent on changes in the screen contents. I can trace out the schematic for the PSU section and go from there if I have to, but having a genuine schematic would be a lot nicer to have! :-) (I've got a 19" CRT on one machine which has a weak tube, so this would be a nice replacement if I can get it running) cheers Jules Open it and look for bad caps by the power supply. That's all I've ever had to replace on a Mag. Good place to start - assuming its a colour monitor, a faulty degauss system can also cause picture shimmer. Most monitors use a 2-pin posistor with a relay to take it out of circuit after a delay - a welded contact would cause it to continue drawing residual current through the degauss coil. Some monitors used the same 3-pin dual posistor as TVs - 1 posistor in series with the degauss coil and the second one direct across the AC mains, that heats the deguass element so it doesn't draw current - a failed heating posistor can cause shimmer. |
#5
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Mag 986FS CRT shimmering picture - schematic?
On Thu, 14 Mar 2013 21:42:25 +0000, Ian Field wrote:
Open it and look for bad caps by the power supply. That's all I've ever had to replace on a Mag. Good place to start Well... it is looking like caps. There weren't any that were showing visual signs of failing, but then of course that's often the way. Sadly my ESR meter's 4,500 miles away (so I've put it on the to-do list to buy another). Anyway, I've replaced the PSU's main smoothing cap and those on the outputs of the 104V and 52V lines using parts from the junk box (which aren't necessarily in the best of shape themselves!), and - so far - that seems to have just about cured things; there are some *very* slight signs of picture instability when scrolling display contents, but far better than before and certainly at a level that I can put up with. I'll give it a week or two and if it's still OK I'll order some new replacement caps. Thanks for the replies, everyone! cheers Jules |
#6
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Mag 986FS CRT shimmering picture - schematic?
"Jules Richardson" wrote in message ... On Thu, 14 Mar 2013 21:42:25 +0000, Ian Field wrote: Open it and look for bad caps by the power supply. That's all I've ever had to replace on a Mag. Good place to start Well... it is looking like caps. There weren't any that were showing visual signs of failing, but then of course that's often the way. Sadly my ESR meter's 4,500 miles away (so I've put it on the to-do list to buy another). Anyway, I've replaced the PSU's main smoothing cap and those on the outputs of the 104V and 52V lines using parts from the junk box (which aren't necessarily in the best of shape themselves!), and - so far - that seems to have just about cured things; there are some *very* slight signs of picture instability when scrolling display contents, but far better than before and certainly at a level that I can put up with. I'll give it a week or two and if it's still OK I'll order some new replacement caps. Its worth seeing how many caps run hot after replacement as well as when determining which ones need to be replaced. The ones that get hot obviously won't last long - sometimes you can take the edge off the ripple current with a polycarbonate on the print side (in parallel with the electrolytic). |
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