Hanns.G Hi221 Monitor - Works For A Second & Then Blank Display

[RetroComputingGrotto]

I've got a Hanns.G Hi221 Monitor that works for a moment and then the display goes off but the power LED indicator remains on. If you power it off and back on again it does the same thing, it comes on and then the display goes blank. From a cold start it takes 10 seconds or so before the display goes blank but if you turn it off and then back on again after it already being on it goes blank a lot quicker so I'm assuming something is getting hot which is causing the display to go off.

I've uploaded a video of it happening on YouTube:

I've taken the monitor apart and have inspected the main board:







As the above capacitor didn't look to happy so I ordered a replacement and swapped it out but after doing a quick test this wasnt the main cause of the issue.


As a lot of electronics of this age that have had heavy use my first port of call was to replace all the electrolytic capacitors (which I have now done) and after doing an initial test I thought it had resolved the problem, but it hasn't...



The problem is still there but it now takes 2-3 hours before the backlight goes off (rather than the 1 minute or so it did before I re-capped it) and if I turn it back on again, the backlight comes on for a few seconds and then goes off.


So to re-cap (punn intended) since replacing all the electrolytic capacitors, from powering it on from cold, the backlight now comes on for an hour or two and then goes off and wont stay on for more than a few seconds.


I'm new to flat screen repairs so looking for some help/guidance from you guys on what could be causing the backlight to fail once the monitor has warmed up...

[CapLeaker]

All you can do here is to resolder the blue caps near the HV connectors for the CCFL's and resolder the 2 transformers. Measure the resistance of the input and output winding of the 2 transformers and compare them to each other. If these are out more than a few percent, the backlights will turn off.
On the picture of the backside of the PSU, there is an IC top right. What's the parts number of it?

[RetroComputingGrotto]

I've replaced those capacitors and resoldered the 2 transformers but that has made it worse! It started off as a couple of minutes, I re-capped all the electrolytics and then it went to several hours before going off and now the backlight stays on for just 2-3 seconds!

This one has defeated me as I need the space on my workbench to repair things in my skillset - at least I've got some more experience with repairing monitors (even if it's negative)! Off to the WEEE it goes, but at least I gave it a try.