0
\$\begingroup\$

enter image description hereI'm -Extremely- new in the DIY Electrics. So go easy on me as I have 0 Electrical Engineering background. Handle me like a 5yo, haha.

I recently decided to give self-repairing the old electronics I have lying around a try. Mainly my old LCD/LED Monitor. Which seems to have power issues.

Symptoms: When plugged in the Monitor LED (Power Indicator) appears to turn on then off after a couple secs.

On a good day it turns on, and remains on and functions normally for a day or 2 then randomly shuts off during use then it would refuse to power on again showing no power LED until after a day or 2 of rest.

Which "LED" me here, haha.

I read that with age (8 year old monitor) the electrolytic capacitors can be the culprit. So I did a tear down and found 2 electrolytic caps on the base (The rest appears to be solid caps). One rated at 33uF/100v and the other 220uF/25v.

Now where I live there are no Frys/ or Radio shacks. So I only have found caps rated at 47uf/400v and 220uF/35v.

I'm hoping the monitor is just a simple case of replacing the caps.

Additional Note: My monitor uses an external power brick (I've tried a different brick, same symptoms). The Capacitors I'm talking about are in the base of the monitor where the power brick connects. The monitor is an HP x2301.

Image Link (Capacitors in RED Outline):

enter image description here enter image description here enter image description here

\$\endgroup\$

closed as off-topic by Dmitry Grigoryev, Sparky256, Dave Tweed Jul 7 '18 at 15:41

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – Dmitry Grigoryev, Sparky256, Dave Tweed
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    \$\begingroup\$ The higher voltage rating is good, the capacitance values will have huge tolerances, so even the values looks good. I only request you to be careful with mains \$\endgroup\$ – Umar Jun 23 '18 at 16:13
  • 3
    \$\begingroup\$ Be aware that polarity matters with these capacitors (one lead is "+", the other lead is "-". Before you remove the old, identify which is which, and be sure to install the new one with the same polarity. \$\endgroup\$ – glen_geek Jun 23 '18 at 16:17
  • 1
    \$\begingroup\$ Most probably yes. Where is it located? \$\endgroup\$ – winny Jun 23 '18 at 16:18
  • \$\begingroup\$ Thanks for the replies! Winny - I dont have time to tear the monitor back down ATM. I did find a rather ugly pic of the board in question. I marked the Capacitors in red. Link - imgur.com/a/ZGuSFsz \$\endgroup\$ – DaemonCross Jun 23 '18 at 16:38
  • 2
    \$\begingroup\$ Before you commit to the 400 volt unit, you need to check the size. A 47 uF/400 V cap will be considerably larger than a 33 uF/100 V part, and may well be too large to allow you to reassemble your monitor. Otherwise, it will work with no problem. \$\endgroup\$ – WhatRoughBeast Jun 23 '18 at 16:47
2
\$\begingroup\$

Large capacitors like that are generally used to filter the powersupply. As such, a little more won't hurt. They will be larger, though, so may not physically fit.

You should stop and consider whether you need to replace them at all, though.

A bad electrolytic capacitor will usually be obvious.

They tend to pop when they go bad. They usually have lines scored on the top, so they "pop" instead of "bang."

Look at yours. If the tops are still flat, then they are most likely OK.

If they are bulged, or some icky stuff has leaked out then they are definitely bad.

If they are bad, they may be difficult to remove.

One pin will probably go to ground. On a multilayer board, that may mean there's a whole layer of copper acting as ground. In that case, it will take a lot of heat to get them out.

What I do is to get out a big 150 watt soldering iron with a big tip - big enough that it can heat both pins at once.

I put MORE solder on the pins, and heat them both. After a while, the whole thing is hot enough that the solder melts on all layers.

You can then pull the capacitor right out. Keep the heat heat on the pads until the capacitor is all the way out.

Replacement goes the same way, but remember that electrolytic capacitors are polarized - you MUST install the new part with the polarization markings exactly as the old ones were.

Lots of solder, heat both holes. The solder will melt all the way through, and you push the capacitor in and the pins all the way through. Keep the heat on the pads until the capacitor is seated in its final position.

Check each connection (eyeball them) and resolder each individually if needed.

Clean up any solder splatters with the soldering iron.

Use alcohol and a stiff brush to remove left over flux.

\$\endgroup\$
  • \$\begingroup\$ Noted! Well the capacitors themselves aren't physically/visually damaged. It's just that the Monitor is pretty old now. I just thought that the caps may already be spent as it was my daily workhorse. As the symptoms show that the monitor in general works display wise, cept that the power when starting up is a dice roll. \$\endgroup\$ – DaemonCross Jun 24 '18 at 3:21
  • \$\begingroup\$ The capacitors in the new photos look OK. \$\endgroup\$ – JRE Jun 24 '18 at 8:07
  • \$\begingroup\$ Yeah, ordered a new multimeter so I can take a capacitance/voltage check. But what else will cause the symptoms I indicated? As the monitor when it does turn on runs fine, no visual glitches or anything else. Just a monitor that's "Moody" if it wants to work or not, haha. Power LED just lights up... then Poofs out. Then it's non-responsive. Leave it long enough, plug it back in... 50/50 chance it lights up and starts. Else same process all over again. \$\endgroup\$ – DaemonCross Jun 24 '18 at 8:24
  • \$\begingroup\$ You will have to take the capacitors out of the circuit to test them. You can disconnect just one pin. That's enough to get good measurements. \$\endgroup\$ – JRE Jun 24 '18 at 8:35
  • \$\begingroup\$ Oh yea, should mention this monitor HP x2301. Runs quite hot almost too hot to touch ever since it was new. So i figure that might accelerate the capacitors drying out or something? Haha. Aight, will do!... Just need that new multimeter to arrive, haha. \$\endgroup\$ – DaemonCross Jun 24 '18 at 8:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.