Can capacitor dielectric be black??

[momaka]

Re: Can capacitor dielectric be black??

Congrats, I'm glad you got it working!

Replaced the 400v filter cap with the new one, didnt bother with the bulb trick as I ordered a stack of those T3.25A 250VAC fuses...

Even if you ordered extra fuses, the light bulb trick is still a very good idea. If there was a fault in the power supply, those components you replaced could have blown again and maybe even more.

Reason why is because those line input fuses are *usually* the last ones to blow - i.e. they blow out only when there is a serious failure elsewhere in the PSU. They are there for protection against fire, not protection of the components in the PSU. The light bulb on the other hand protects the PSU components (at least for a short amount of time).

Nichicon.. Doesnt sound like a name that would be synonymous with "reliability" does it..

Other than some problems with their HM and HN series that have now been corrected (only HM and HN series manufactured between 2001 and 2004 were affected), Nichicon is a very very reliable brand.

[ben7]

Re: Can capacitor dielectric be black??

This was a tricky one as the cap in the original was a low profile. One of the electronics providers here didnt even have a size compatible cap.

This is the one that I went with

http://radionics.rs-online.com/web/p/aluminium/7529511/

Nichicon.. Doesnt sound like a name that would be synonymous with "reliability" does it.. .. but it was cheap. I didnt want to buy anything more expensive in case there were other issues with the screen.

Good choice there!

[JonathanAnon]

Re: Can capacitor dielectric be black??

What brand capacitor did you use as a replacement?

This was a tricky one as the cap in the original was a low profile. One of the electronics providers here didnt even have a size compatible cap.

This is the one that I went with

http://radionics.rs-online.com/web/p/aluminium/7529511/

Nichicon.. Doesnt sound like a name that would be synonymous with "reliability" does it.. .. but it was cheap. I didnt want to buy anything more expensive in case there were other issues with the screen.

[ben7]

Re: Can capacitor dielectric be black??

Wohooooooo... it's alive...

My supplier didnt have 2amp diodes, so I ordered 3amps... I read somewhere that even though there are only two that have shorted, it's best practice to replace all four rectifiers... which was a bit of a job given that the 3A were considerably bigger, but managed to squeeze them in by temporarily removing the inductor. Fitted quite snugly in the end..

Replaced the 400v filter cap with the new one, didnt bother with the bulb trick as I ordered a stack of those T3.25A 250VAC fuses... Put it all back together, and here's badcaps on my working screen.



Thanks for the help :-)

Good job bro!



What brand capacitor did you use as a replacement?

[JonathanAnon]

Re: Can capacitor dielectric be black??

Wohooooooo... it's alive...

My supplier didnt have 2amp diodes, so I ordered 3amps... I read somewhere that even though there are only two that have shorted, it's best practice to replace all four rectifiers... which was a bit of a job given that the 3A were considerably bigger, but managed to squeeze them in by temporarily removing the inductor. Fitted quite snugly in the end..

Replaced the 400v filter cap with the new one, didnt bother with the bulb trick as I ordered a stack of those T3.25A 250VAC fuses... Put it all back together, and here's badcaps on my working screen.



Thanks for the help :-)

[JonathanAnon]

Re: Can capacitor dielectric be black??

And now I pretty much just plug things in. Only if I've done something very risky then I would use the extension cord.

Haha, that's my most important piece of equipment. Only had one bang so far, when I cleverly replaced a fuse in a Dell Monitor with a jump wire.... Pity really cos I reckon it was an easy fix if I'd just waited, got another fuse (to prove that it wasnt actually just a worn fuse causing the problem), and then start to troubleshoot it properly... And that's exactly what I DONT want to do this time..

[momaka]

Re: Can capacitor dielectric be black??

Yeah I was thinking about trying to work in a bridge rectifier as a test, but I'm yet to fix my first screen ( ) so I'm not brave enough yet.

Ah yes, I know that feeling very well . First time I fixed a monitor (it was just 4 bad caps), I had it plugged in a extension cord with an ON/OFF switch and I was wearing safety goggles and had a fire extinguisher next to me. Had the room all quiet too in case something went wrong so I could hear it.
...
And now I pretty much just plug things in. Only if I've done something very risky then I would use the extension cord.
The safety goggles are the only thing I still won't take off. But I don't think I am over-protective here - electrolytic caps installed in reverse will pop/burst. Even worse, the monitor may appear to work but it won't be until a few seconds after that they'll pop.

With the light bulb in place of the fuse, the only disappointing thing that could happen is that you won't get exciting fireworks if something was wrong. Instead, you'll just get a lit bulb. *boring*
The only exception to that is electrolytic caps installed in reverse.

[JonathanAnon]

Re: Can capacitor dielectric be black??

Got any scrapped PC power supply boards? You can salvage a bridge rectifier off one of them. And most likely I think the 1A diodes won't cut it.

I have both a 20 pin and a 24 pin ATX power supply here and both have the rectifier as a single unit.

That should be fine for testing purposes, as long as it has the proper ratings (2A and at least 400V reverse blocking voltage). Just make sure you wire it right ( + to +, - to -, and the two ~/AC lines to AC).

Yeah I was thinking about trying to work in a bridge rectifier as a test, but I'm yet to fix my first screen ( ) so I'm not brave enough yet.

The 1A diodes may also work for testing. Granted you're in Ireland, you have 230 VAC mains. Unless that power supply is to provide more than 230 W, the 1A diodes should be fine. However, the only problem that might arise is that those diodes may blow up during the initial plug-in due to the large current spike.

I'm think I'm just gonna order the new diodes rather than risk trying the 1A.. I was looking online have these in my basket 1N5408 ... Just have to process the order. ..

I will definitely be using the bulb trick though, as after replacing the diodes I will have replaced.... - Main filter cap. - fuse - two diodes... So there could very easily be something else blown.

[momaka]

Re: Can capacitor dielectric be black??

everything else I have here has a bridge rectifier, not the individual diodes.

That should be fine for testing purposes, as long as it has the proper ratings (2A and at least 400V reverse blocking voltage). Just make sure you wire it right ( + to +, - to -, and the two ~/AC lines to AC).

The 1A diodes may also work for testing. Granted you're in Ireland, you have 230 VAC mains. Unless that power supply is to provide more than 230 W, the 1A diodes should be fine. However, the only problem that might arise is that those diodes may blow up during the initial plug-in due to the large current spike. But you can get around that - just remove the fuse and connect a regular household light bulb to it instead. If there isn't a problem, the light bulb will flash then turn off and the power supply should be outputting the proper voltages. If there is a problem, the light bulb will stay lit - in that case, don't keep power connected to the power supply too long.

You can use that light bulb trick even when the new parts arrive. In fact, this is a very good method to save you from blowing parts if something is wrong.

[ben7]

Re: Can capacitor dielectric be black??

Stuff arrived for this today, fuses and 400V cap. Have to order those diodes as well I think, nothing similar here.. Closest I can get is this IN4007 diode which I took from the rectifier of another piece of electrical equipment... but it's only 1A.. everything else I have here has a bridge rectifier, not the individual diodes.

Got any scrapped PC power supply boards? You can salvage a bridge rectifier off one of them.

And most likely I think the 1A diodes won't cut it.

[JonathanAnon]

Re: Can capacitor dielectric be black??

Stuff arrived for this today, fuses and 400V cap. Have to order those diodes as well I think, nothing similar here.. Closest I can get is this IN4007 diode which I took from the rectifier of another piece of electrical equipment... but it's only 1A.. everything else I have here has a bridge rectifier, not the individual diodes.

[JonathanAnon]

Re: Can capacitor dielectric be black??

Did you check the bridge rectifier? that could have gone bad and caused the capacitor to blowup.

The PS is a Vestel as was suggested by some sharp eyed person earlier.. It's a 17IPS15-4, and they put in rectifying diodes, with no BR. It is two of the rectifying diodes that are blown. D801 and D802 (both RL207 ) in the following document. The rest of the diodes seem fine.

http://elektrotanya.com/vestel_17ips.../download.html

[ben7]

Re: Can capacitor dielectric be black??

Okay, just to update.. thanks again to all who have helped..

I plugged in the TV after replacing the 400V cap and the fuse... Switched it on and nothing happened... Tested the fuse and it was blown. So for the past three hours I've been going through the components trying to test them...

I've found two diodes that are shorted. I'll see if I can find replacements.

Did you check the bridge rectifier? that could have gone bad and caused the capacitor to blowup.

[JonathanAnon]

Re: Can capacitor dielectric be black??

Okay, just to update.. thanks again to all who have helped..

I plugged in the TV after replacing the 400V cap and the fuse... Switched it on and nothing happened... Tested the fuse and it was blown. So for the past three hours I've been going through the components trying to test them...

I've found two diodes that are shorted. I'll see if I can find replacements.

[JonathanAnon]

Re: Can capacitor dielectric be black??

http://omg.wthax.org/26072012901.jpg

Just soldered in the 400v cap and 3.25A fuse from the XBOX in to the LCD Screen.. What do you think Ben, do you foresee any problems getting the cover back on.. .. the original cap was 25mm, this one is 40mm.. I'll power it on and see what happens.

[JonathanAnon]

Re: Can capacitor dielectric be black??

If you don't have a spare 3.25A fuse, just use a 3A to 2A fuse to test it. One thing is for certain, NEVER put in a bigger size fuse!

There's a 3.15A 250V fuse on this XBOX board as well.. I assume it would be fast blow (same as the monitor).. surely no reason for it to be time delayed?

[ben7]

Re: Can capacitor dielectric be black??

See, I picked up an old XBOX today (which has a 400V 150uF cap), having already ordered the 400V 68uF cap and the 3.25A fuse from radionics. They should be here on Friday.

The 400v 150uf cap is certainly way too big for the TV, it's wayyyyyyyy too tall. But it would have worked as a nice test before I made the purchase.. I could throw it in place of the 68uF cap and put a 60W bulb in place of the fuse... I might just try it anyway..

If you don't have a spare 3.25A fuse, just use a 3A to 2A fuse to test it. One thing is for certain, NEVER put in a bigger size fuse!

[JonathanAnon]

Re: Can capacitor dielectric be black??

See, I picked up an old XBOX today (which has a 400V 150uF cap), having already ordered the 400V 68uF cap and the 3.25A fuse from radionics. They should be here on Friday.

The 400v 150uf cap is certainly way too big for the TV, it's wayyyyyyyy too tall. But it would have worked as a nice test before I made the purchase.. I could throw it in place of the 68uF cap and put a 60W bulb in place of the fuse... I might just try it anyway..

[ben7]

Re: Can capacitor dielectric be black??

I have them ordered, so put your chips on the table please.. :-)

I have a 400v 150uF cap. Could I use this instead.. I thought the higher the capacitance the better the filter job it would do?

Sure you can, as long as it has enough space!

[JonathanAnon]

Re: Can capacitor dielectric be black??

I always though the common failure mode for those high voltage caps is open circuit rather than short circuit.

Crap-caps love to go short-circuit and draw excess current

I have them ordered, so put your chips on the table please.. :-)

I have a 400v 150uF cap. Could I use this instead.. I thought the higher the capacitance the better the filter job it would do?