drewcam888
EE Nerd
Last Activity: 11-24-2012, 10:00 AM
Joined: 10-02-2009
Location: Indiana
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Dell 1901fp No Picture
I have a 1901fp that doesn't have any picture. The led goes green when pushed. If you look closely the screen flash what looks like a thin (a couple pixels wide) pixelated line vertical down the center of the screen. The PS seems ok and I see no caps on any of the boards that look suspicious. I suspect the screen itself but was looking for any suggestions. -
Re: Princeton VL1812 Monitor
Replaced KA1M0565R and power supply is great now. Now just to fix the color being way off. -
Re: Has the Dell 1800FP exhibited bad caps?
So I got another 1800fp the other day. It just so happens to have a bad logic board also. I was hoping for the PS but I wasn't that lucky. This one won't turn anything on, no leds or screen. The backlight is ok because I can jumper it on and the PS is giving good voltages. Has anyone heard of a solution for this one. I am beginning to think the main IC is fried on this one.Leave a comment:
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Re: Has the Dell 1800FP exhibited bad caps?
Jump stick a wire in the 5v out from the power supply and pin 8 of the inverter plug and the backlight will come on.Leave a comment:
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Re: Princeton VL1812 Monitor
As bill said there it is a 4 pin device....Leave a comment:
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Re: Princeton VL1812 Monitor
I think the 431 is ok. I am looking into the 4 pin smpsLeave a comment:
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Re: Princeton VL1812 Monitor
Diodes seem ok. I took the three out and they tested fine. The only ones I didn't remove were the four rectifying diodes. So now I will look at the IC or transformer.Leave a comment:
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Re: Princeton VL1812 Monitor
Most testing has been done without a load. But I then just plug the power supply into the logic board for a load. I will have to look into your possible solutions.Leave a comment:
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Re: Princeton VL1812 Monitor
Entire recap done minus a used cap in parallel for the main ac line. And still no constant voltage.Leave a comment:
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Re: Princeton VL1812 Monitor
So since I have limited caps again. I placed two 47uf is parallel where the 100uf was. The voltage now does not vary nearly as much. So that helps. But isn't the entire solution. So I am not for sure were to look next. I guess I just might recap everything.Leave a comment:
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Re: Princeton VL1812 Monitor
So according to that Cfb matters. Even though it is a nonelectrolytic i might check it. The electrolytic I changed seems to matter to. It does it is Ccc on the Vcc pin of the switch. This is a great app note.Last edited by drewcam888; 10-15-2009, 01:18 PM.Leave a comment:
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Re: Princeton VL1812 Monitor
Well maybe the voltage is right near 10V but it is way close to the rating. It may be higher when it actual starts to work right.
Boy do I wish I could edit posts older than 10 minutes. It makes me post much more than needed. Has it always been that short.Leave a comment:
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Re: Princeton VL1812 Monitor
I replaced the C808. It was a 100uf 50v. I only had a 470uf 50v so it is in there now with no help. I just found some under rated caps also. Caps C817 and C814 are 10V when the voltage from the rectifier is sometimes current 11.7ish. I will fix that.Last edited by drewcam888; 10-15-2009, 11:07 AM.Leave a comment:
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Re: Princeton VL1812 Monitor
It is a KA1m0565r. I attached datasheet....Last edited by drewcam888; 10-15-2009, 11:01 AM.Leave a comment:
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Re: Princeton VL1812 Monitor
Attached is the photos of top and bottom. As you can see there are no components on the bottom.
I will try and figure out which cap he is talking about in #13. I guess i don't know which cap to change because I don't really have this SMPS controller or at least I don't think I have what bill thinks I do....Last edited by drewcam888; 10-15-2009, 09:48 AM.Leave a comment:
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Re: Princeton VL1812 Monitor
When you say smps controller. I dont have a big ic like the schematic. The opto just drivers a 4 pin TO220 power switch that drives the transformer. So you want me to look at my TO220 IC?Leave a comment:
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Re: Princeton VL1812 Monitor
With that voltage dropping an repeating I see a small voltage appear on the isolated side of the opto. I can't tell for sure if the voltage at the opto is caused my the low voltage 8.6ish or the high voltage 11.7ish. I guess i need a scope so I can see where the edges line up. It is kinda working it see a low voltage then tries to go higher but then quites again. I dont see the cause of this.Leave a comment:
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Re: Princeton VL1812 Monitor
Th voltage goes from 8.6ish to 11.7ish then down to 8.6 in 2 seconds then back to 11.7 immediately and repeats over and over.Leave a comment:
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Re: Princeton VL1812 Monitor
Well I soldered in a cap that I think is good. Still ticks maybe I need to find a new one.
So there was a 100uf cap from VCC to gnd on the four pin switch that drivers the transformer. I didnt have a 100uf so I put in a 470uf and the 12 supply now varies more than before. Boy am I confusing myself today.Last edited by drewcam888; 10-14-2009, 01:20 PM.Leave a comment:
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Re: Princeton VL1812 Monitor
I will look into the large cap. It isnt the inverter because it does it without an inverter hooked up. I also dont see any voltage at the because the voltage never reaches 2.5V. So on to your other suggestions.Leave a comment:
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