Flickering could be due to the flyback, could be due to a lot of other things. A missing colour is certainly not the flyback, though. Here are some simple-ish faults and possible causes. There are plenty of other causes for these faults, but this is what I'd check first. Missing colour (only 2 of the 3 guns working) ---- Bad cable or PC plug (bent pin) Dry joints on the CRT base panel (Where the video amplifier normally is) Defective components (transistors, LM1203 chip, etc) in the video amplifier CRT (unlikely) Horizontal line (only) ---- Vertical output chip Capacitors near the vertical output chip open/shorted No power to vertical output chip (maybe fusible resistor O/C) Vertical line (only) --- If EHT comes from the horizontal output, then O/C yoke, connector, or coupling components. If separate EHT generator (fairly common in monitors with multiple scan rates, including even EGA), then horizontal output transistor, drive to it. Blank screen, power on light normal --- Look for glow from CRT heater. If missing, check supply (maybe from the flyback, maybe from the main PSU) and heater continuity Check EHT with a special EHT meter. Expect about 25kV on a colour monitor, about 12kV - 15kV on a mono one. If missing, check flyback, horizontal output transistor, etc Check other CRT voltages. If any are missing, trace back to the source (probably from the flyback). It's possible, although rare, for a video amplifier fault to bias the CRT beyond cut-off. Sometimes turning up the 'screen' control will get a raster in this case. Blank screen, power light flashing about once a second --- The main PSU is tripping (assuming this isn't some infernal power-save mode). Most likely cause is the horizontal output transistor shorted, probably due to a shorted flyback. Main fuse blows violently ----- Short on the primary side of the PSU : Chopper transistor, bridge rectifier diodes, degaussing posistor, chopper control module, etc. Sort this out like an SMPSU Flickering, especially when case is tapped ---- Dry joints (could be just about anywhere). Often a complete resolder is the quickest way to solve this. www.repairfaq.org is down at the moment (I believe the amount of data pulled from that site exceeded the limits set by the ISP). There are mirrors, but I forget where. A quick search of sci.electronics.repair will find them, though. FInd that site and read the safety warnings before you pull the case on a monitor. There are dangers in them - high voltages (not just the EHT to the CRT, but also mains), the high-vacuum CRT that could implode (although it's unlikely), etc. Normally, when a flyback fails, it develops shorted turns and kills the horizontal output transistor as well. You don't need an EHT probe to find that. A ringing tester will find shorted turns, but you need a 'scope. -tony

Interesting... It sounds like a high-voltage problem to me. I had a VGA monitor where the focus and brightness went all over the place as it warmed up. I traced it in the end to the flyback, which cost rather a lot to replace :-(. Anyway, in most monitors the focus supply (5kV or thereabouts) comes from the flyback. As does the EHT to the CRT. And the EHT voltage does affect the size of the picture (higher EHT -> `stiffer' beam -> smaller picture for a given deflection field). What I'd do is find the supply to the horizontal output stage. This is probably around 150V. Having a service manual (what is the monitor, just in case I have the schematics?) helps. If that drifts as the monitor warms up, then debug the power supply. If it's steady, suspect a problem with the divider network in the flyback. -tony

Tony Duell wrote: well. Probably 6 of 10 monitors I work on are flyback related, 2 are the power supply and the rest are varied between bad controls, horiz or vert sections, or cheap digital touch controls.

On Sun, 27 Sep 1998, Tony Duell wrote: Fixed freq. workstation monitor, used for Sun, old SGI, etc. I have the specs from mine: Max res: 1280x1024@60Hz Vfreq: 59.90Hz Hfreq: 63.34KHz

There are adapters available to use these things with PC's and MACs too, but I guess if it's been dropped, well... I got mine for $45 and it's OK. A little fuzzy and one corner is starting to fade. I spent $35 on a 13W3=>DB15 converter and am much happier using my 17" NEC Multisync on my Sparc 5.