Replaced Caps and made things worse...

**Th3_uN1Qu3** · 01-11-2011, 10:11 AM

Re: Replaced Caps and made things worse...

The clicking isn't a relay, it comes from the switching transformer because the controller is continuously restarting (protect mode). Recheck your soldering, you've shorted something.

**retiredcaps** · 01-11-2011, 11:13 AM

Re: Replaced Caps and made things worse...

Originally posted by Spode

After replacing the caps, now it won't switch on at all - I just get a repeated clicking maybe once a second?

What brand and series did you use for replacement caps? SMPS power supplies require low ESR capacitors.

**ben7** · 01-12-2011, 08:28 AM

Re: Replaced Caps and made things worse...

you should check your soldering for bridges, and also check if there is a short on any of the +V rails to ground with a DMM.

-Ben

**Behemot** · 01-12-2011, 08:33 AM

Re: Replaced Caps and made things worse...

Check if you did not changed cap polarity somewhere, I keep doing this all the time and than search for the problem for hours :-)

Sometimes the problem is also when you increase the capacity somewhere and it's bad place this time (usualy controlling cirtcuits, sometimes there are high-capacity caps which you could count as output ones).

**Spode** · 01-15-2011, 03:28 PM

Re: Replaced Caps and made things worse...

Hi Guys,

Not sure why I didn't get an e-mail with this responses - I subscribed!

The capacitors I bought were from Maplin - couple of Jamicons that had 105c temperature ratings. The other two are CapXon caps I took from another PSU that I sacrifice bits from.

Polarity wise - I've soldered negative to the shaded half on the PCB, which is the same as the other capacitors on the board. It also looks that way following traces.

I've also matched the capacity exactly.

From what I recall - I'm getting the noise even with the capacitors removed - which suggests the problem lies elsewhere? Perhaps a piece of wire that flew off into the PCB? Sounds like I've shorted something out somewhere - so I'll take a look around...

**Behemot** · 01-15-2011, 03:34 PM

Re: Replaced Caps and made things worse...

Could be it.

Jamicons and CapXons is not good replace, you'll probably have to change them again sooner or later.

**Spode** · 01-15-2011, 05:16 PM

Re: Replaced Caps and made things worse...

Okay - I pulled it out, gave it a good going over with the hair dryer, then completely re-did the soldering of the caps. It was a pretty tight area in there due to a heatsink above it, so this time I soldered in some wire so I could house the caps separately. I looked it over with a fine tooth comb for shorts and plugged it back in, but no difference.

I then realised that two of the connectors that plug into the board were identical. I looked at the length of the two and realised there was a high chance I had reconnected them the wrong way around... :P

I swapped them around and no more shorting noise!

However, replacing the caps hasn't solved the problem. It shuts down in less than 1 second and the LED indicates that it is going into standby.

The PSU itself is a little bit of a high pitched noise when in action - a sign of a leaky cap perhaps? Other than the main 450V one on the PCB, there aren't many more.

Quite a few toroid coils on the board - so my next guess would be to touch each of these up. Any other suggestions?

**Behemot** · 01-15-2011, 05:28 PM

Re: Replaced Caps and made things worse...

Have you connected the switch panel if it's detachable? When I had a Samsung display here last time, I had to have it connected and actually turn the display on otherwise it kept itself in standby.

I don't think the problem is in the PSU anymore, it probably won't give any voltage at all if it didn't work. As for the noise, i won't say it's unusual, my LG back in home does the same when it's in standby. When it's running, the noise has higher frequency due to the higher switching frequency. Just cheapo trafos etc.

**Spode** · 01-15-2011, 05:43 PM

Re: Replaced Caps and made things worse...

Yeah - it's all connected (quite a simple layout).

The backlights and a blue screen flash on a for a split second and you can just about see the LED turn green.

I've just done all the toroid coils with no luck.

Would not using low ESR caps (at least, I don't think I have) cause this?

I can see one more suspect cap but it's really difficult to get to. It looks flat, but looking close at it and putting a knife blade over the top of it, I believe it could be VERY mildly bulged. IT's right next to the 450V main cap - so it could be quite important. The caps I replaced were so bulged it was crazy.

**Behemot** · 01-15-2011, 05:51 PM

Re: Replaced Caps and made things worse...

It's best to replace everything when you're recapping it. Usually just the input capacitor (the 400/450V one) is fine and do not need to be replaced.

As for the rest, well, I doubt Jamicon and other crap manufacturers started to make caps which really correspond their datasheets. That's one of the reason we don't use them. But it could be something else, the best thing you can do now is to take good photos od the boards (from both sides) and upload them here.

**retiredcaps** · 01-15-2011, 05:52 PM

Re: Replaced Caps and made things worse...

The clicking and high pitched whine suggest that the little capacitor is bad or going bad. It will be near the big cap.

This cap is in the range of 22uF 50V or something like that. They can fail without signs of bulging.

A clear focused picture using managed attachments would help a lot. Please do not post pictures inline.

**seanc** · 01-15-2011, 05:56 PM

Re: Replaced Caps and made things worse...

Those Jamicons from Maplin are not Low ESR or suitable for a PSU. I know, I have some.

You need Panasonic FM, FC, or FK aluminium electrolytic capacitors.

**Behemot** · 01-15-2011, 06:04 PM

Re: Replaced Caps and made things worse...

You could also use Samxon RS/GT/GK, Nichicon HE/HD, Chemi-Con KZE/KY/LXZ/LXY/LXJ, Rubycon ZL/YXG/YXH or Sanyo WA/WX.

**Spode** · 01-15-2011, 06:06 PM

Re: Replaced Caps and made things worse...

Originally posted by retiredcaps

The clicking and high pitched whine suggest that the little capacitor is bad or going bad. It will be near the big cap.

This cap is in the range of 22uF 50V or something like that. They can fail without signs of bulging.

It sounds like a high pitched whine, which pulses periodically.

I'm not sure pictures would help much TBH - as there are two large aluminium heatsinks that cool the mosfets that cover most of the PCB. It looks too complex to remove too.

I think I can replace the cap next to the main 450V capacitor by desoldering and then soldering a new one in on wires to the back of the PCB.

Originally posted by seanc

Those Jamicons from Maplin are not Low ESR or suitable for a PSU. I know, I have some.

Not suitable or not ideal? Would it cause the issue I'm seeing? Where is the best place to get them in the UK? I've been using Maplin just because I don't buy many and there is one right next to my house...

**Behemot** · 01-15-2011, 06:18 PM

Re: Replaced Caps and made things worse...

Originally posted by Spode

Not suitable or not ideal? Would it cause the issue I'm seeing? Where is the best place to get them in the UK? I've been using Maplin just because I don't buy many and there is one right next to my house...

Both. There is usually some tolerance and it could work if you are within it. When you go over it, it won't work. This may be the reason.

**Spode** · 01-15-2011, 06:34 PM

Re: Replaced Caps and made things worse...

I just removed the other cap I was talking about near the 400V. It's 400v 15uf and isn't bulged in the slightest.

I have found low ESR replacement for the other caps I replaced (may as well try!), but I can't find a low ESR 400V 15uf anywhere! Could I get away with a higher capacitance or could this be timing related?

**Behemot** · 01-15-2011, 06:46 PM

Re: Replaced Caps and made things worse...

This one was in parallel to the bigger one or what?

I don't think this one have to be low ESR, it probably flattens the input 50/60 Hz current.

**Spode** · 01-15-2011, 06:52 PM

Re: Replaced Caps and made things worse...

Originally posted by Behemot

This one was in parallel to the bigger one or what?

I don't think this one have to be low ESR, it probably flattens the input 50/60 Hz current.

No connection on the back, and I can barely see the front. I'll just have to go for something normal.

Struggling at the moment because Farnell want a minimum order of £20 and I have nothing else I want to buy!

**seanc** · 01-16-2011, 05:41 AM

Re: Replaced Caps and made things worse...

Have you checked RS Components? I don't think they have a minimum order and shipping is usually around £5 I think.

Replaced Caps and made things worse...

Replaced Caps and made things worse...

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