Monitor power supply problems

[topperdude]

Hi,

I have a Westinghouse LCM-22w2 monitor that stopped working recently. When I turn on the monitor, there's nothing on the display, none of the lights come on, nothing! The first one or two times when I tried to plug it into different outlets to test, I did hear a high-pitched sound (capacitor going bad?) but not anymore.

On going through some of the posts on these forums, I suspected whether the power supply might need to be repaired. So, I opened up the monitor last night and sure enough looks like atleast two of the capacitors have gone bad. See images below:

Power supply board - DAC-19M009 BF
Badcaps closeup

I also read a posts here which suggested it might be worth it to replace ALL capacitors instead of just the ones that are obviously bad. So, I plan to order the following capacitors that I found on the power supply board:

1000uf 10v capacitor x1
2200uf 10v capacitor x1
220uf 25v capacitors x3
1000uf 25v capacitors x2
330uf 25v capacitor x1

Would appreciate some advice on few questions regarding the repair:
1. Is it possible (or even advisable) to test whether any additional parts besides the capacitors might have also gone bad? Or should I replace the capacitors and see if it fixes the problem before trying to diagnose any other parts?

2. In addition to the solder on the PCB, there seems to be some white stuff holding the capacitor to the board on the top side. Is it OK to remove this? If so, what might be the best way to remove the capacitor from this and is there some precaution I should take while doing so?

3. I recall reading somewhere that even though Radioshack might probably sell the capacitors with the correct ratings, it might be better to get better quality ones (Panasonic, Nichicon, etc) from an online supplier. I looked through the badcaps website and they dont seem to have all the needed capacitors in the various brands they carry. Any suggestions of other websites where these could be purchased?

I am familiar with soldering/de-soldering having done it for couple years in school on various projects and then for occasional repairing of speaker PCBs and such, but do not do it on a day-do-day basis. So any additional advice to help the recapping go smoothly would be appreciated.

Thank you,
-Topper

[seanc]

Re: Monitor power supply problems

Badcaps.net
RS Components
Digikey
Farnell
Mouser

I always buy Panasonic - FM is the best line, then either FC or FK if you have issues with size. Check the ripple rating and buy the highest where possible if you're having to make a choice.

I would replace the caps first. If it's still dead, then we can troubleshoot.

[topperdude]

Re: Monitor power supply problems

Thanks for the reply!

Am looking at digikey's catalog - I dont see ripple listed as a filter - would ripple be the same as Tolerance?

Thanks,
-Topper

[seanc]

Re: Monitor power supply problems

Ripple isn't the same as tolerance.
If you have a look at RS Components, you'll see a column 'Ripple current'. There doesn't seem to be a filter for that on Digikey.

[topperdude]

Re: Monitor power supply problems

Spent some time over the weekend going through the various recommended websites to find one that might have all of the replacement capacitors needed.

Am getting ready to finalize my order with Digikey as they had almost all the replacement capacitors needed and the two that are out of stock are expected by 03/16/2010 so hope to have the capacitors sometime this week.

In the meantime, I would like to de-solder the current capacitors on the board and get it ready when the replacements come in. Would appreciate some advice on the following question from my original post.

2. In addition to the solder on the PCB, there seems to be some white stuff holding the capacitor to the board on the top side. Is it OK to remove this? If so, what might be the best way to remove the capacitor from this and is there some precaution I should take while doing so?

Per further 'googling' over the weekend, I understand the white stuff (see attached image) might be an adhesive like RTV162 to hold the capacitor to the board (please correct me if I am wrong)? Wonder what might be the best/safest way to remove it before removing the existing capacitors, without damaging any other components or the board? Also, any suggestions for similar product that can be purchased at Home Depot, etc to hold the replacement capacitors in place?

Thanks,
-Topper

[PlainBill]

Re: Monitor power supply problems

Spent some time over the weekend going through the various recommended websites to find one that might have all of the replacement capacitors needed.

Am getting ready to finalize my order with Digikey as they had almost all the replacement capacitors needed and the two that are out of stock are expected by 03/16/2010 so hope to have the capacitors sometime this week.

In the meantime, I would like to de-solder the current capacitors on the board and get it ready when the replacements come in. Would appreciate some advice on the following question from my original post.


Per further 'googling' over the weekend, I understand the white stuff (see attached image) might be an adhesive like RTV162 to hold the capacitor to the board (please correct me if I am wrong)? Wonder what might be the best/safest way to remove it before removing the existing capacitors, without damaging any other components or the board? Also, any suggestions for similar product that can be purchased at Home Depot, etc to hold the replacement capacitors in place?

Thanks,
-Topper

You're over complicating the process. The 'white stuff' IS glue; it was used to hold the parts in the board as it went through the insertion > inspection > wave solder manufacturing steps. You already have the 'stuff' to hold the replacement in place. I use the index finger of my left hand; others have reported success using the ring finger. (One degenerate preferred to use the middle finger; that is frowned upon in polite company).

PlainBill

[topperdude]

Re: Monitor power supply problems

You're over complicating the process. The 'white stuff' IS glue; it was used to hold the parts in the board as it went through the insertion > inspection > wave solder manufacturing steps. You already have the 'stuff' to hold the replacement in place. I use the index finger of my left hand; others have reported success using the ring finger. (One degenerate preferred to use the middle finger; that is frowned upon in polite company).

PlainBill

PlainBill,

Thanks for the response!

I am more concerned about properly removing the 'white stuff' glue before desoldering the capacitors without damaging any other components (for example the component sandwiched between the two bulging capacitors marked as '3R3' in the picture attached in my previous post).

Thanks again,
-Topper

[sofTest]

Re: Monitor power supply problems

I use a sharp knife of the type with break-away sections (not sure what they are called in English), and cut along the side of the capacitors, so they come loose when I desolder the capacitors. After desoldering, I trim away some more glue.

[mu2]

Re: Monitor power supply problems

Hi,

I've got the same monitor with a backlight problem, same inverter board.
When you get it going could you measure the primary and secondary resistances of both inverter transformers?
I've got .4 ohms on both primaries and 360 ohms on both secondaries. That primary resistance seems too low to me - I found a bad dual mosfet - the 8 pin IC which is an AOP 605. Both mosfets were replaced and the transformers swapped. Same two seconds to black problem - caps have all been replaced with FM series.
I'm suspecting the transformers - but could both be bad? With shorted primaries?
Anyone know a source for the transformers? They are marked 2874001100, MB 638A - could be Delta.

Thanks for your help,

Mike

[PlainBill]

Re: Monitor power supply problems

PlainBill,

Thanks for the response!

I am more concerned about properly removing the 'white stuff' glue before desoldering the capacitors without damaging any other components (for example the component sandwiched between the two bulging capacitors marked as '3R3' in the picture attached in my previous post).

Thanks again,
-Topper

I've never had a problem. It's a pretty poor glue. Most of the time it breaks up real easily. Otherwise I use a small screwdriver to pry it away from the cap I'm replacing.

PlainBill

[topperdude]

Re: Monitor power supply problems

My order with digikey has not shipped yet since two of the FM series capacitors (1000uf @ 25v and 2200uf @ 10v from my list below) are on backorder. On Monday (March 15) when I talked to them, they were expecting them in stock by March 16 and ship out some time this week. Today when I called, it seems their Panasonic contact person looked into this further and confirmed they are in transit but will be delivered to digikey on 03/22 after which they will be shipped to me.

Wondering if:

• Its worth it to wait till 03/22 to get the FM series capacitors (since the ones on backorder are the ones that are bulging/gone bad) or

• should I substitute the FM series caps with different caps they currently have in stock (Panasonic FC series, Nichicon, etc). Main reason for doing this would be so Digikey can ship them today and the caps can be delivered by Saturday via USPS priority to me (same state) and I can try repairing the monitoring over the weekend.

• If I do substitute the caps, should I change the entire order and stick with same series across the board (e.g. all FC series) or is it OK to mix/match capacitors from different series, especially for this application (i.e. monitor inverter)?

Would appreciate any input.

Thanks again!
-Topper

[PlainBill]

Re: Monitor power supply problems

My order with digikey has not shipped yet since two of the FM series capacitors (1000uf @ 25v and 2200uf @ 10v from my list below) are on backorder. On Monday (March 15) when I talked to them, they were expecting them in stock by March 16 and ship out some time this week. Today when I called, it seems their Panasonic contact person looked into this further and confirmed they are in transit but will be delivered to digikey on 03/22 after which they will be shipped to me.

Wondering if:

• Its worth it to wait till 03/22 to get the FM series capacitors (since the ones on backorder are the ones that are bulging/gone bad) or

• should I substitute the FM series caps with different caps they currently have in stock (Panasonic FC series, Nichicon, etc). Main reason for doing this would be so Digikey can ship them today and the caps can be delivered by Saturday via USPS priority to me (same state) and I can try repairing the monitoring over the weekend.

• If I do substitute the caps, should I change the entire order and stick with same series across the board (e.g. all FC series) or is it OK to mix/match capacitors from different series, especially for this application (i.e. monitor inverter)?

Would appreciate any input.

Thanks again!
-Topper

Look at the thread 'Which capacitors should I buy' in the FAQ. Choose an equivalent part that is in stock from as far to the right in the list as possible. Panasonic FCs would be an acceptable substitute, but see if you can find something better. Mixing brands is no problem, the manufacturers do it all the time.

PlainBill

[topperdude]

Re: Monitor power supply problems

Look at the thread 'Which capacitors should I buy' in the FAQ. Choose an equivalent part that is in stock from as far to the right in the list as possible. Panasonic FCs would be an acceptable substitute, but see if you can find something better. Mixing brands is no problem, the manufacturers do it all the time.

PlainBill

Thanks for pointing out that link, PlainBill. Although useful to get a general idea of the different series, it appears that list might not have been updated in some time now (since 2006)? Many of the online sites (digikey, mouser, newark) seem to have series from various manufacturers that are not listed in that post. Similarly, series listed in that post that are not listed at the online sites.

In any case, I ended up not substituting the backordered capacitors (for the time being). I remembered I had few other electronics devices that had stopped working and got to thinking whether they might have blown capacitors as well (and if so, add the caps for those to the backordered order at digikey to try repair them).

For instance, I have a pair of Zyxel PLA-400 ethernet adapters and one of them stopped working few months back. Decided to open it up last night and sure enough looks like atleast one of the 1200uf @ 6.3v caps is bulging (see attached pictures). So I started creating a list of capacitors used in that device and here's what I came up with:
6.3v 1200uf, 5mm lead spacing, ~15mm (height) x10mm (diameter) (x2)
25v 100uf, 2.5-3mm lead spacing, ~12.5mm (height) x5mm (diameter) (x1)
400v 6.8uf, roughly same dimensions as the 6.3v capacitors (x2)

Would appreciate any suggestions/advice on which capacitors I should replace on that board from those listed above? Initially, I thought I would replace all the capacitors listed above with better ones from digikey. However, I read somewhere (probably on this forum) that the higher voltage capacitors near the power supply input usually do not need to be replaced as it could be dangerous doing so if they have some residual voltag? Is this true? Or would it make sense replacing the 400v capacitors?

Another question - what is the black cylindrical component in front of the two 400v capacitors (see closeup image attached). It looks like a capacitor but does not have ratings marked on it (atleast not that I can easily see). Wondering if it might be a capacitor and if so whether I should replace it as well and where I would find ratings for it?

Interesting thing I noticed was that the blown capacitor was not mounted as flush with the board as the other capacitors (marked in one of the attached images). As a result, there really wasnt much clearance between the top of the capacitor and the top cover of the PLA-400 and in fact the capacitor could have touched the top plastic cover of the unit. In fact, when the capacitor failed, some of the electrolyte got stuck to the top cover of the PLA-400. could improper installation have contributed to the capacitor failure??

Thanks for the continued feedback and suggestions. Looks like recapping could get addictive, especially if I am able to successfully fix these two devices with just replacing their capacitors

-Topper

[PlainBill]

Re: Monitor power supply problems

Thanks for pointing out that link, PlainBill. Although useful to get a general idea of the different series, it appears that list might not have been updated in some time now (since 2006)? Many of the online sites (digikey, mouser, newark) seem to have series from various manufacturers that are not listed in that post. Similarly, series listed in that post that are not listed at the online sites.

In any case, I ended up not substituting the backordered capacitors (for the time being). I remembered I had few other electronics devices that had stopped working and got to thinking whether they might have blown capacitors as well (and if so, add the caps for those to the backordered order at digikey to try repair them).

For instance, I have a pair of Zyxel PLA-400 ethernet adapters and one of them stopped working few months back. Decided to open it up last night and sure enough looks like atleast one of the 1200uf @ 6.3v caps is bulging (see attached pictures). So I started creating a list of capacitors used in that device and here's what I came up with:
6.3v 1200uf, 5mm lead spacing, ~15mm (height) x10mm (diameter) (x2)
25v 100uf, 2.5-3mm lead spacing, ~12.5mm (height) x5mm (diameter) (x1)
400v 6.8uf, roughly same dimensions as the 6.3v capacitors (x2)

Would appreciate any suggestions/advice on which capacitors I should replace on that board from those listed above? Initially, I thought I would replace all the capacitors listed above with better ones from digikey. However, I read somewhere (probably on this forum) that the higher voltage capacitors near the power supply input usually do not need to be replaced as it could be dangerous doing so if they have some residual voltag? Is this true? Or would it make sense replacing the 400v capacitors?

Another question - what is the black cylindrical component in front of the two 400v capacitors (see closeup image attached). It looks like a capacitor but does not have ratings marked on it (atleast not that I can easily see). Wondering if it might be a capacitor and if so whether I should replace it as well and where I would find ratings for it?

Interesting thing I noticed was that the blown capacitor was not mounted as flush with the board as the other capacitors (marked in one of the attached images). As a result, there really wasnt much clearance between the top of the capacitor and the top cover of the PLA-400 and in fact the capacitor could have touched the top plastic cover of the unit. In fact, when the capacitor failed, some of the electrolyte got stuck to the top cover of the PLA-400. could improper installation have contributed to the capacitor failure??

Thanks for the continued feedback and suggestions. Looks like recapping could get addictive, especially if I am able to successfully fix these two devices with just replacing their capacitors

-Topper

I doubt that contact with the plastic case had anything to do with the failure of the cap. I'd replace all the caps; ordinarily I don't replace the 400 volt caps; they rarely fail and cost several dollars each. These are only $.75 from Digikey.

The unknown component is an inductor. Very unlikely to fail.

PlainBill

[topperdude]

Re: Monitor power supply problems

Finally got my capacitors yesterday. I am using a soldering iron quite similar to the one recommended here on badcaps.

Wondering what I can use to clean the oxidation from the tip of the iron? Someone suggested using this Hakko Tip Cleaner but dont have any stores locally carrying it and would prefer not delaying the project past this weekend waiting for this to arrive from an online store. Would it be possible to get a similar brass based cleaning wire/sponge at a local store such as Home Depot or Radioshack?

Alternatively, would something like this brass brush at Home Depot or
this tip tinner/cleaner at Radioshack work?

I have tried wet sponge but that didnt seem to help cleaning the tip a whole lot so I am guessing there's a bit more oxidation on the iron than what can be cleaned with the wet sponge.

Would appreciate some advice/suggestion.

Thanks,
-Topper

[topperdude]

Re: Monitor power supply problems

Thanks to the advice and information in this and other threads on this forum (as well as some other sites), it looks like recapping the inverter board with the capacitors above has fixed the monitor!

I do have one additional question before putting the monitor back in service - I used this 60/40 rosin core solder from Radioshack. I dont have any pictures of the recapped board currently (since I had reassembled the monitor in my eagerness to test whether it works before realizing that the flux residue might need cleaning), but one or two of the solder holes seem to have noticeable amounts of (I think) rosin flux (looks dark brown and seemed sticky just after I finished soldering all the capacitors). As far as I can tell, the residue is mainly around the respective solder leads and residue from two leads are not touching.

I have read where some posts suggest that the residue should dissipate/evaporate on its own due to heat whereas others seem to suggest that heat could cause it to run and create short circuit or other issues on the board.

Is it advisable to remove the residue before using the monitor? If yes, what would a recommended product to remove the flux from the solder linked above.

Thanks again,
-Topper

[PCBONEZ]

Re: Monitor power supply problems

Thanks for the reply!

Am looking at digikey's catalog - I dont see ripple listed as a filter - would ripple be the same as Tolerance?

Thanks,
-Topper

Digikey links you to a PDF data-sheet that will have the ripple current rating. Look to the right end in a search result.

Ripple Current Ratng tells you how much Ripple Current the cap can pass without overheating internally.
- Kind of- the same meaning/purpose/idea as a watts rating on a resistor.
.

[PCBONEZ]

Re: Monitor power supply problems

Wondering what I can use to clean the oxidation from the tip of the iron?

In a pinch you can tightly wrap & tape around a roll of toilet paper and use the end of the roll as a wipe pad.
Yeah it burns a little and stinks but it works surprisingly well.

That's an old Navy ET trick for when the supply guy doesn't keep stocked up and you run out of those supplies underway.
.

[topperdude]

Re: Monitor power supply problems

Digikey links you to a PDF data-sheet that will have the ripple current rating. Look to the right end in a search result.

Ripple Current Ratng tells you how much Ripple Current the cap can pass without overheating internally.
- Kind of- the same meaning/purpose/idea as a watts rating on a resistor.
.

Thanks for the response PCBONEZ. However, as I mentioned in my last post, I have already purchased the capacitors and re-capped the board. What I am now wondering is whether I need to clean the residue (possibly from the 60/40 rosin flux in the solder linked in my last post?) before using the monitor and what the risks might be of not cleaning it? If cleaning the rosin flux residue is reccomended, what product should I used to do so?

Thanks again,
-Topper

[PCBONEZ]

Re: Monitor power supply problems

Is it advisable to remove the residue before using the monitor?

Yes

If yes, what would a recommended product to remove the flux from the solder linked above.

Use isopropyl alcohol & cue-tips.