Instructables

Step 6: Replace the faulty capacitors!


Dell used surface mount electrolytic capacitors on this monitor. They are no different than regular electrolytic capacitors, only a plastic bottom part which enables robots place components on the board.

We will start by replacing two capacitors: 10uF 16V... I heard that most of the time this replacement is enough to make the LCD work again. These two capacitors are labeled as C604 and C507. If changing these won't help, you may try to replace remaining capacitors.

Prepare your soldering iron, solder, utility knife (or something else to cut the capacitor legs short). Start heating your soldering iron...

And the capacitors! Here is the list of all electrolytic capacitors that Dell 1702FP has on board:

2 pieces 10uF 16V (critical ones)
6 pieces 22uF 16V
4 pieces 100uF 25V

STEPS:

De-solder the old capacitors! Polarity is printed on the board, so you don't have to pay attention to polarity when you are de-soldering the faulty ones.

Reshape the legs of the new capacitors into T figure. Trim the long legs, so you'll have legs only long enough to sit on the circuit board firmly.

Solder the capacitors on the circuit board. Pay attention to the polarity. All electrolytic capacitors come with polarity signs on them. Put them on the board in correct direction, otherwise they will blow up. Look at the last photos on this step, these are new capacitors in place.

 
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dgluck2 years ago
Great teaching. On my now dark 1702FP, the capacitors are much smaller than the black one in your pic (C604) and silver/black colored. And the leads don't seem to go all the way thru the board. Can they be soldered on the same side as the capacitor rather than on the back of the board as I expected? Thx. :Dani
Nightshade7 years ago
Could I use a 35w vdc cap. When I bought the caps they only had one 16w. COOL Instructable. Thanks
Short answer: yes. The w goes with the vdc and is, thus, wvdc (working volts direct current). So the designation is actually 35 wvdc = 35 volts. The thing that makes the working voltage important is that voltages higher than the rated wvdc may cause a breach of the dielectric (insulation) between the layers of the capacitor. Think of a capacitor as two sheets of aluminum foil with a sheet of waxed paper separating them. If the voltage between the two aluminum foils becomes too high, a spark will pop through the waxed paper and that will be the end of that! It is not practical to make capacitors of arbitrarily high voltage tolerance because of expense and size constraints. The voltages inside computer circuitry once we get past the power supply are less than twelve volts for the most part. That's why 16 volts is a good number for most applications. If the 35 wvdc capacitor will fit in the space, it should be just fine.
I bought all the caps you mention but only replaced the two caps at c604 and c507 to get my 1702FP working again. Here's the link to where I got my caps: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=020-1014%20%20%20%20%20%20%20&FTR=020-1014&CFID=10534636&CFTOKEN=52523994

I used a 15w soldering iron and some fine silver solder I had laying around.

Thanks a lot for the Instructable!
shello5 years ago
Hi K, Your instructions and steps are excellent and clear for the DEll 1702FP monitor, however the symptoms described with the BLEDS are the same for me with my Dell E550 CRT Monitor. Do you have any experience with this monitor and what capacitors should I change to rectify the problem? Your feedback would be appreciated. Thanks.
DKW5 years ago
Something I have found over the years I have spent repairing electronics is that using Electrolytic Capacitors rated at about twice the working voltage of the device is best. The voltages of the above named Capacitors are only 2 volts above the working voltage of the Monitor witch is 14 volts. The least voltage I would use is 25 volts, and if I have room I would use cap's rated at 35 volts. Remember the Capacitance is generally critical, And never use a capacitor rated at a lower working voltage then your project. Allelectronics.com is a great parts source.
thearchitect (author)  DKW5 years ago
Excellent point! Thanks for contributing! K.
hacster7 years ago
Hey Thearchitect.. You simply are a genius. Thank you for a very very usefull guide Best regards Hacster
hi, there are vertical lines in my 17 inch L.C.D. monitor. please tell me how to fix it
really cool, but I'm stuck. After ripping the thing apart with my bare hands (ok.... maybe not, but I feel like it.) I actually have an HP 1702 but this got me going in the right direction. Reading up on the problem links to to caps as well. After scanning the circuit board and a funny orange one about twice as large, I can't find a single bad cap, or anything of that matter. Does anyone have any experience with this? I will post some pictures if I get a response by someone. (anyone notice that the HP 1702's look really cool when out of the ugly black housing? Stick two of those together and voila!)
Nanuq7 years ago
Wow what a great instructable! You rock! So, this is related, but not exact (I don't think). My monitor power quit working the other day. After finding out that its no longer on warranty, I decided to take it apart and see if I could do anything. Now, I know a bit about computers but not so much about circuit boards and electronic stuff. There are a number of components that look like short AA batteries, with a plastic jacket and a metal top with an X on them. One of these components has obviously shorted out (or something); it is brown on the top instead of shiny metal and has a bit of crud on it. So...what exactly is this component, can it be replaced and how would one (or one's husband who is more electronically inclined) go about fixing/replacing it? Oh, and it is on a Dell 1905FP LCD monitor. Thanks so much and keep up the great work!!
thearchitect (author)  Nanuq7 years ago
Thanks for your nice comments! I am glad that my efforts helped some people to rescue their monitors! From your description, your issue sounds like a blown up electrolytic capacitor. If it is the only part that's faulty, then very easy to replace. Someone with decent soldering skills can do the job easily. Electrolytic capacitor replacements are easy to find, try to find with same capacity and with equal or higher voltage rating. Check electronic parts shops for that. If you can take the old one out with you, and if it is not badly burned/damaged, shop owners can help you with finding the correct replacement. Be careful on polarity when installing, otherwise the new one will blow up, too. Most printed circuit boards have polarity indicators (+ -) labeled on them. Good luck! K.
Hi K, I thought I could fix my DELL LCD monitor lying in the basement for over an year. I opened it - But the PCB is different : Its a 1701FP and not 1702. There are many more capacitors - Any ideas? TIA
Hi K. the architect :-) OK, hoping you can give me further advice. I replaced 2 blown capacitors and now I appear to have power to the monitor and maybe a backlight (?) but still no input from the cpu. Any marvellous advice?
michajoh7 years ago
Thanks, instead of trashing a good monitor, I put < $3 of parts and a little time and my flat panel is back in business. I only needed the 2 10s. Anything on a compaq tft8020?
darimini7 years ago
I couldn't find the capacitors listed here at Radio Shack. I did find this 10µF 16V 20% Dipped Tantalum Capacitor, but when I went to the store, I noticed that it did not have any polarity indicators on it. And Radio Shack doesn't have any 22uF 16V capactors or 100uF 25V capacitors.

So: (1) Are Tantalums "neutral" or something? (2) Where are you guys buying your capacitors?

Thanks!
thearchitect (author)  darimini7 years ago
Hi there, I don't think Tatalums would work. By the way, 90% of chance you only need one or two 10uF 16V capacitors. The type you need is electrolytic. Easiest for you in the States is to get them from www.Digikey.comwww.Digikey.com.

If you want it from Radioshack, this type may be compatible with what you need: Radioshack Model: 272-1025
Catalog #: 272-1025, or link: 10uF electrolytic

Pay attention to polarity when soldering. First change the 10uF near the upper left corner of the circuit board. Then replace the other one on the upper right side.

Cheers,

Koray.
thearchitect (author)  thearchitect7 years ago
As far as I know, as long as you have the capacity and type (i.e., electrolytic) right, voltage doesn't make much difference for capacitors. You can use higher voltage substitutes for lower voltage parts. But not vice-versa. Cheers, Koray.
Thanks! Since I've posted, I found out that my blinking LED (I have a Dell E173FPb) is more likely a result of bad C5707 transistors. So now, since people are charging an arm and a leg for them (since they're in demand from this common problem), I'm trying to find an inexpensive alternative. If anyone could help with that, thanks! If not, thanks anyway!
xenoalien7 years ago
Does it show the polarity on the capacitor as a - and +?
xenoalien7 years ago
What type of solder should I use? Is there a good brand?