LCD Monitor - Blues Screen + Rippling lines after Cap replacement

Thread Starter

Liquid Fusion

Joined Jun 24, 2019
6
Hi. Dell SE2717H - Black screen. Vertical scratchy lines flowing down.

Replaced 470uF 25v with Radio Shack 470uF 35v. Blue desktop. Descending horizontal ripple flowing lines. Replaced the 220uF 25v cap with a 470uF 35v. Same Desktop Blue screen. Descending horizontal ripple flowing lines. How come the capacitor replacement didn't work? Thanks.
 

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jpanhalt

Joined Jan 18, 2008
9,409
Let me guess, you replaced C917 and C904 (shown) plus C801 and C906 (guess based on soldering). Were they all the same size?

Some of those solder joints look like you had too cool an iron or didn't wait for good flow. You could try redoing them, but that may not fix the problem. Maybe the problem is something else?
 

Thread Starter

Liquid Fusion

Joined Jun 24, 2019
6
Thanks! Picked the caps I replaced. Yes replacements all were 470uF 35V caps. Can try to resolder. Soldering iron was set to the middle of the dial (Tabiger 110V 25-60 Watts) 300F. What temp do you like to use? Any soldering tips?

C906 looks like it's touching E21. Causing a short? Was it ok to replace the 220uF 25v cap with a 470uF 35v Cap?
 
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jpanhalt

Joined Jan 18, 2008
9,409
"E21" is actually 123 or a 12000 ohm resistor. They look like they are intended to be connected on that large copper pour. If you remove the solder using solder wick, that may be clearer. Generally, 300°F is too low a temperature for ordinary solder. I keep my iron set to 740°F (about 393°C). Are you sure it is Fahrenheit, not Celsius?
 

Thread Starter

Liquid Fusion

Joined Jun 24, 2019
6
Might be C. Turned iron up all the way. 60 watts. Redid soldering. Solder I used came with the iron. resoldered by reheating. Added Radio Shack resin core 60/40 0.032" to C801. Checked C906 is not touching 123. Looks that way in screenshot.
 

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Thread Starter

Liquid Fusion

Joined Jun 24, 2019
6
Same vertical downward rippling. Thought maybe I could correct the cap replacement. Possibly the damage is another component. Ordered replacement power board off Ebay. 24.49 vs buying a new monitor.
 

jpanhalt

Joined Jan 18, 2008
9,409
$24.49 is cheap compared to trouble shooting some other problem. As for the 220 uF vs. 470 uF capacitor, the allowable tolerances on such capacitors is very large, and if they are simply power supply filters, going larger usually won't matter.

Are you using leaded or lead-free solder? Leaded solder is generally easier to get a nice looking joint. I prefer the 63/37 alloy, but 60/40 is used by many people too.
 

Thread Starter

Liquid Fusion

Joined Jun 24, 2019
6
Solder from the iron manufacturer and also Radio Shack. 60/40 Sn / Pb - yes there is lead (Pb). What other things would you troubleshoot? Have a ACDC Multimeter from Radioshack. Ordered an inexpensive multimeter that tests AC/DC,ohms, and continuity as well.

Cen-Tech 7 Function Digital Multimeter = 4.00
https://www.google.com/shopping/product/9933273701357072766

DT-830B Mini Pocket Digital Multimeter 1999 Counts AC/DC Amp Volt Ohm Tester Ammeter Voltmeter Multi Meter = $1.54
https://www.aliexpress.com/item/32961170868.html?
 

jpanhalt

Joined Jan 18, 2008
9,409
Having those meters won't help much unless you have a schematic and/or troubleshooting guide. Such guides will show you test points and usually what voltage should be present. There may be additional directions, such "jumper x to y and check z." If you can get the shop manual for a late model car or farm implement, you can see what I am talking about. It is hardly worth the time for consumer electronics, which is why most things are "board level" trouble shooting today.
 
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