Secondary monitor flickering off intermittently with iMac - Mac-Forums.com

iggsta · 11-07-2009, 01:08 PM

Hi everyone,
I've been running a secondary monitor from the mini-display port of my 24" intel Mac for a few weeks without problems. I'm using a VGA connection and a third-party mini-display port/VGA converter from eBay. I'm outputting to a digimate 24" screen, capable of 1920x1200.

Trouble started when I noticed very thin horizontal lines on the 2nd monitor. These have now stopped but the screen briefly turns black intermittently (the power doesn't go off). These blackouts only last around 1-2 seconds, and only happen when the monitor is set to 1920x1200. On 1680x1050 I haven't experienced any blackouts.

I've tried installing the firmware update Apple provided for mini-display port/VGA conversion but I was presented with a message saying no converter was detected? Could this be because my converter isn't official?

Any help would be greatly appreciated.
Dominic

iggsta · 11-07-2009, 01:57 PM

Just have to add that I'm now getting blackouts on 1680x1050 too, so doesn't look like a resolution issue...

Mint · 11-07-2009, 02:27 PM

My brand new 27" iMac had horizontal lines flickering through and also the odd blackout. I downloaded the latest performance update and it seemed to of stopped. Couple of hours later it was back. This morning I switched it on and have been using it for around 8 hours so far without 1 flicker or 1 blackout. The performance update didn't solve it because it also happened after it. It is quite a large problem and has been posted numerous times on the apple discussions but I haven't been able to find apple saying anything about it. I made a thread on here about my problem last night and it hasn't had 1 reply. :/

iggsta · 11-07-2009, 03:05 PM

Yeah I've seen similar posts elsewhere but no solutions yet. I'm tempted to try an official converter but that's another £20 and seems like a bit of a gamble.... If I contact apple support they'll probably blame my monitor or the converter but I'm fairly sure the monitor is fine as I use it with my PC and get no problems. Do you know if similar problems have been reported with Mini-display port/DVI conversions?

iggsta · 11-07-2009, 03:26 PM

Can I ask, have you tried the firmware update from the apple site?
Mini DisplayPort to VGA Firmware Update

I try installing but get the message:
'The Updater could not find a Mini DisplayPort to VGA Adapter to update.
Check that the adapter and external monitor is connected, and on, and then retry'