Iiyama VisionMaster 405 (S705MT) full of G-Luxons

[Rainbow]

I have an Iiyama VisionMaster 405 monitor (model S705MT) bought in 2002 (made in 2001). It was working fine (except for the DDC which never worked) - but it has a strange problem now. It looks OK in high resolutions (1152x864@85Hz) but is very dim in lower resolutions (like standard text mode).
When I power the computer up, I see last part of the POST, then the white Windows ME logo which goes dim slowly. After switching to high resolution, the brightness goes up slowly back to almost-normal level. If I switch to full-screen DOS prompt, I see normal brightness for a moment and then it dims - exactly like during boot. The OSD menu is dim too. When I adjust the brightness and contrast to MAX values, it's blurry and really does not look nice.
I opened it up today just to see if there aren't any bulged caps. All caps are G-Luxon - but they all look OK, not even a slightest sign of bulging...

[Chris1992]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

Weird.... Why are you running WinMe? and what's DDC?

[Rainbow]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

WinME - because that's the latest version where all the hardware (SCSI scanner, SB AWE64, Bt848A video capture card) and software (DOS games ) works properly.
DDC = Display Data Channel = plug&play for monitors. I traced the SDA and SCL signals from the VGA cable all the way to the microcontroller (or whatever that is - many pins and has metal shield/heatsink on top) - so either the microcontroller is bad or is not correctly programmed.

[kc8adu]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

is the hv generated independent of h sweep?
if not look to the s correction area.
thats the mosfets that switch caps to retune the h out stage.

[Rainbow]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

Today, the monitor was running and suddenly poofed and then produced silent hissing, even for a while after turning off. The picture on the screen was normal. It smelled like a bad cap, however. So I opened it and found bulged G-Luxon 2200uF/25V. I took it out and not only it's bulged but the rubber from the bottom is half way out and leaking electrolyte. So I replaced it with 2200uF/35V Taicon taken from 1995 monitor - so it's not a new badcap but still nothing very good most likely. It works now, no new poof
But it didn't solve the original problem - that still remains the same. I was unable to find any service manual or schematic.

[Rainbow]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

And the photos

[Rainbow]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

Of course it was caused by bad caps. The 6.3V heating voltage was too low - started at 1.8V after power up and slowly rised to 3.2V (and maybe a bit more). It was caused by bad C924 (100uF/16V @85 degC G-Luxon showing 100ohms ESR) in 6.3V power supply. It was placed inside the heatsink of LM317. Replaced with 470uF/16V @105 degC and no more brightness problems

[yanz]

Re: Iiyama VisionMaster 405 (S705MT) full of G-Luxons

congrats! that small 100uf caps could be evil. i replaced them on some mobo (arround pci or bios jumper) with lxz 680uF and no more restart problem (unable to restart from OS or unable to wake up after power outage).