Dell E197FPf - Colors Faint, White Washed Glare, Slight Ghosting - W/Pictures
Hi guys,
I'm a bit stumped here.
-Scrapheap-destined Dell 19" E197fpf monitor that wouldn't power on at all.
-Found the 12V->5V DC-DC converter IC had failed (AP106 ).
It was outputting 11V to the rest of the cct. The 3.3V and 1.85V regulator outputs were still fine.
-I replaced it with a LM2575 1A Fixed-5V version. (). First time the monitor worked beautifully for about 10 minutes then died. Found the 5V regulator had died again.
-Didn't have my ESR meter yet so I replaced most of "secondary-side" electrolytic caps with rubycon LOW-ESR equivalents. The one cap that I didn't replace has subsequently turned out to be ok anyway.
-Then put in a new 5V LM2575 and it blew within a few seconds. Couldn't find anything obvious around the LM2575 that might cause it to blow. So I decided to remove it from the cct and inject 5V from a bench power supply.
-Monitor powers up, but screen is completely white. No OSD visible. Plugging in a VGA signal makes no difference.
-After reading more posts checked the fuse on the T-CON board and sure enough it was blown. Maybe by the 11V input from the blown regulator?
-Checked the T-CON board for any obvious shorts that might cause the fuse to blow again, found none, so installed a new SMD Time-Lag 1.5A fuse.
-Powered everything on and things are looking better, except that now the display is very washed out. Almost as if the brightness is up too high. Colors are faint etc. I have attached a photo of it side-by-side with my usual rig for comparison.
-I later picked up two mistakes I made with the regulator. First - I'm pretty sure the original component was an ADJUSTABLE version. The markings on the IC are inconclusive but there are two resistors making up a voltage divider and the feedback pin is connected to the middle of those. I thought that perhaps this was why when I installed the FIXED-5V version it kept blowing? The FIXED-5V expects it's feedback pin to be connected directly to the output (via inductor). Anyhow... another mistake was that the original IC was rated for 3A, and the one I put in is only 1A. Could this be a problem? The bench power supply never seemed to go much over about 750mA so I wasn't sure. It is capable of 3A though.
-Not feeling like trying to source the ADJUSTABLE version I "modified" (cringe!) the PCB to use a 5V fixed regulator. Essentially by-passed the divider and plugged the feedback pin into the inductor output. At least the regulator isn't dying, and is putting out 4.95V. From what I could calculate with the original resistors on the board the adjustable version would give 5.085V so about 100mV difference there.
-Tried factory defaults reset, even factory program mode, color adjust, rgb etc, no difference.
Any ideas?
I'm a bit stumped here.
-Scrapheap-destined Dell 19" E197fpf monitor that wouldn't power on at all.
-Found the 12V->5V DC-DC converter IC had failed (AP106 ).
It was outputting 11V to the rest of the cct. The 3.3V and 1.85V regulator outputs were still fine.
-I replaced it with a LM2575 1A Fixed-5V version. (). First time the monitor worked beautifully for about 10 minutes then died. Found the 5V regulator had died again.
-Didn't have my ESR meter yet so I replaced most of "secondary-side" electrolytic caps with rubycon LOW-ESR equivalents. The one cap that I didn't replace has subsequently turned out to be ok anyway.
-Then put in a new 5V LM2575 and it blew within a few seconds. Couldn't find anything obvious around the LM2575 that might cause it to blow. So I decided to remove it from the cct and inject 5V from a bench power supply.
-Monitor powers up, but screen is completely white. No OSD visible. Plugging in a VGA signal makes no difference.
-After reading more posts checked the fuse on the T-CON board and sure enough it was blown. Maybe by the 11V input from the blown regulator?
-Checked the T-CON board for any obvious shorts that might cause the fuse to blow again, found none, so installed a new SMD Time-Lag 1.5A fuse.
-Powered everything on and things are looking better, except that now the display is very washed out. Almost as if the brightness is up too high. Colors are faint etc. I have attached a photo of it side-by-side with my usual rig for comparison.
-I later picked up two mistakes I made with the regulator. First - I'm pretty sure the original component was an ADJUSTABLE version. The markings on the IC are inconclusive but there are two resistors making up a voltage divider and the feedback pin is connected to the middle of those. I thought that perhaps this was why when I installed the FIXED-5V version it kept blowing? The FIXED-5V expects it's feedback pin to be connected directly to the output (via inductor). Anyhow... another mistake was that the original IC was rated for 3A, and the one I put in is only 1A. Could this be a problem? The bench power supply never seemed to go much over about 750mA so I wasn't sure. It is capable of 3A though.
-Not feeling like trying to source the ADJUSTABLE version I "modified" (cringe!) the PCB to use a 5V fixed regulator. Essentially by-passed the divider and plugged the feedback pin into the inductor output. At least the regulator isn't dying, and is putting out 4.95V. From what I could calculate with the original resistors on the board the adjustable version would give 5.085V so about 100mV difference there.
-Tried factory defaults reset, even factory program mode, color adjust, rgb etc, no difference.
Any ideas?
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