More Elec. Cap Failures

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A day ago, the Pan. HD recorder failed to light. Opened the hood last night to find another case of cap failure. The first one I saw was on the far left edge of photo 1. Next I pulled the HD & cage and discovered the others below it:





Manuf. date is April 2004. Not all caps are showing signs of failure, however since the PS board feeds the unit + HD, I'll be recapping it to keep from having to do this again. Panasonic did a nice job here in their PS design by including a LC line filter and transient protection.

Time to warm up the iron.........
 
Originally Posted By: Chris142
Can you explain to a dummy how to know what to look for?


The bulged-top capacitors.
 
When the top part of capacitor is "bulging", that means it is bad, some may rupture also.

To OP, depends on the application, if you can find a higher voltage capacitor with the same capacitance, that may prevent you from re-capping in the future. Replace 10V with 16/20V or whatever is available at higher voltage?
 
Last edited:
Originally Posted By: Chris142
Can you explain to a dummy how to know what to look for?
In photo 1, most caps appear to have evenly shiny tops. The bad ones have one quadrant that's dark grey. Reason is their top is no longer flat, thus not evenly reflecting light.

On the side shots you can see the 'bulge' easier, especially the one that's leaked meaning the top expanded enough to rupture the "curve" stamped into it. The manuf. does this to give it a place to expand. Also makes it more noticeable.

However even a smooth top cap can have a high ESR and/or the value can be too far out of spec. I'll cut a few open after getting this repaired.

For an internal view of a failed cap, see my other thread on "Parasound".
 
Originally Posted By: JMJNet
To OP, depends on the application, if you can find a higher voltage capacitor with the same capacitance, that may prevent you from re-capping in the future. Replace 10V with 16/20V or whatever is available at higher voltage?
Yep. I did this on my post regarding the Parasound...replaced 65V caps with 80V.

Also on my fuel pump relay fix. Replaced 16V cap with 25V. (16 is way too low.....)

My line voltage here is about 125VAC. Some older equipment is designed around "110VAC". Higher V means increased thermal dissipation, which can shorten life. This was a HUGE problem in the HK Citation 7 I posted about here years ago. The heat badly damaged the ckt board, cooked several components and caused the thermal fuse in the main PS transformer to melt! It's being fed a lower VAC now and is given a hard off to shut the PS down when not in use. Otherwise the PS is on 24/7, dissipating lots of heat. That's bad design...
 
I've changed so many I have lost count. I think they (the defective ones, https://en.wikipedia.org/wiki/Capacitor_plague ) were in the supply chain long after the supply was supposed to have been fixed. I see Wikipedia is now saying through 2007. My favorites have been TEAPO and CAPXON. They seem to always be failed in anything I open up. Never seen any repeat failures with quality replacements (assuming no design issue).
 
Years ago when I was in electronics I remember the SMPS circuits would get a leaky cap in the voltage regulation feedback circuit (usually a low value cap like a 1u or a .47u) and that allowed the voltage to creep up blowing other filter caps in the power supply.
When you change your caps be sure the output voltages of the power supply are correct.
 
Never knew this was a recognized phenomenon. I was an IT tech back then and diagnosed many Dell Optiplex computers that had this problem.
 
I was going to say... nature of the beast, no?

Will be looking forward to repair shots. Resoldering parts on boards is a great skill.
 
Manufacturers like Panasonic, Sony, etc, can pick electrolytic filter capacitors that have a specific life, ie, so they pop
in 3-4 yrs etc, thus you buy a new TV etc. Seen that. Cheap computer motherboards go that route a lot.

The PS board (power supply) is typically a high frequency "switch-mode" power supply that no longer uses a
heavy 60Hz line transformer. These caps see high switching frequencies and currents, so if you recap, look for
"Low ESR" caps, meaning "low effective series resistance" plus the voltage rating, capacitance value and temperature rating on them.

High switching currents in the cap generates heat that over time gases the electrolyte bulging the case at the top, you'll note
the cases have grooves on top, so they can 'burst' but not explode old-school. We're not talking a lot of heat here an extra 1/4 watt
will age a cap that should be stone cold. Electrolytic caps also have significant Inductance and Resistance that becomes a big
issue when ripple currents can be several Amps at 30 to 50 KHz!

Low ESR caps take more time to get, but will last way longer. Ebay will show some results if you search "low ESR cap", etc.
 
The Panasonic PS used in this player isn't a switcher. Good old linear.

I've been buying parts from Mouser for decades now. Also from Digi-key. They only stock NEW parts. EB can be such a [censored] shoot. If I'm going to spend the time, I'll only use top grade, new parts, from a major supplier like Mouser or Digi-key.
 
Yup,

I've recapped my panasonic plasma TV 2.5 years after I got it. Funny thing is the large 420V reservoir caps tested fine in my lab, but had bulged tops. I ordered some new ones (Nichicon long life) and they arrived with bulged tops. they tested fine as well with equal ESR as the original ones.
frown.gif


Found some smaller innocent looking ones that had residue on the pcba near the leads. Those turned out to be the culprit.

Another issue I found was the heating system. My TV had fans that turned slowly to not make noise but they plugged with dust and no longer cooled the electronics. Heat is also a strong factor in capacitor life.

its been 7 years since I recapped and its been working fine. Really wish it would die so I can upgrade to one of the OLED TVs out not.
smile.gif
 
Originally Posted By: Chris142
Thanks I never knew about bulging caps
You're welcome.

Reason I posted here is for education. Confusers aren't the only component afflicted. Many other devices were as well. Learning to spot this will allow you see it for yourself.
 
https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors

If I recall the story correctly a Chinese company stole a formula for making electrolytic capacitors, but didn't get the whole manufacturing process. But the URL has a much more accurate account than my memory. It says a Chinese company stole it from a Japanese company, then a Taiwanese company stole it from the Chinese company, mis-copying the formula as they left.
 
Dell wasn't the only one involved: Apple got hit hard too. I know because I pulled the MB out of a 17" iMac and replaced about 17 EC's. Still works to this day. The previous owners didn't take advantage of Apple's offer to fix it all for free. Thus their >$2000 investment failed within about 4 yrs or so. It would cost more to fix than it was worth.

The original PS in a Dell Optiplex SFF I bought post-financial-lease a few years back did the same thing. New PS's from them were no longer being made. I remember arguing the point with one of their female reps "our engineers have indicated no problems with this PS nor date code. We would know...."

I informed her that this engineer (EE) had done his own investigation, found the defective EC in their PS and would gladly offer pictures. Further, if a NEW PS WAS available by all means point me to it on their site. She wasn't able to do that....

I don't pull my EE card often however it is rather amusing (up to a point) when some business idiot wants to take me to task regarding an area they know nothing about. She quickly found herself way out of her league and granted my request for a $50 credit towards my earlier purchase of a Dell machine....that was promised as "fully refurbished".

Yea, right..........

i = C(dV/dt)

Caveat emptor
......
 
the board in the picture is indeed an smps.
a good replacement cap would be panasonic fc series.
i have seen elna caps leak at the bung but these are the first i have seen bulge/vent.
Originally Posted By: sleddriver
The Panasonic PS used in this player isn't a switcher. Good old linear.

I've been buying parts from Mouser for decades now. Also from Digi-key. They only stock NEW parts. EB can be such a [censored] shoot. If I'm going to spend the time, I'll only use top grade, new parts, from a major supplier like Mouser or Digi-key.
 
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