More Elec. Cap Failures

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My apologies to KC8ADU & I.H.Autofraud! You gents are indeed correct. The PS is a switcher. All of the 'early' filtering between the cord & switch driver is to contain the noise. I have a similar linear supply with the coils, line caps and xnsfrmr. My brain immediately went to it.

Thanks for setting me straight!
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Thanks for sharing this knowledge. I am glad someone asked how to tell if a capacitor is bad.

I have an old home stereo receiver that I suspect has at least one bad cap. It hums and has a lot of scratchy noise for about 10 to 15 seconds when I first turn it on. Sounds good after that.

A local electronics repairman just retired about a year ago and I don't know anyone around to take my receiver to. I have a lot to learn about electronics..
 
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.


I hear ya bro! Mouser or Digi-key are good sources.

But checking the pics you posted, show a slit-core ferrite transformer, these won't work well at 60Hz, you
got a small simple forward-mode switcher PS there, the simplest there is. On the low volts DC side, there
will be parts like a linear IC (chip) regulator, etc. The only way to bulge caps in an all linear PS is either lots of heat
that also darkens the circuit board or running the caps just over their rated voltage.



In
 
Originally Posted By: Reddy45
Never knew this was a recognized phenomenon. I was an IT tech back then and diagnosed many Dell Optiplex computers that had this problem.

[off-topic]
....You too?
[/off-topic]
 
I don't recall opening any mainstream, OEM PC (2000 vintage and newer, not anything after about 2012) that doens't having failing caps on the motherboard and / or power supply. The performance will deteriorate before complete failure too, as you get more noise AC riding on the DC voltage. I think the power supplies (OEM and aftermarket) are worse than the motherboards. The power supplies of the flat panel monitors are just as bad too.
 
Originally Posted By: CorvairGeek
The power supplies of the flat panel monitors are just as bad too.
Yes. That includes and also explains why many flat panel televisions are Tango Uniform after a relatively short life. Watched a guy recap a dead inverter ckt that brought it back to life.
 
I've had to change the caps in all our monitors at home, and even my work monitor (it was just easier and faster for me to do it). Some of them will give you some warning, as they will start to flicker when first turned on.
 
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Few years ago when I was re-doing vintage audio/stereo gear, caps replacement was a common thing to do as well as the caps in speakers. Seems a lot of the 70s & 80s gear it was just time. The most common was deoxit the pots/switches & replacement lamps to LED. Always go for the quality brand parts.
 
Originally Posted By: sleddriver
Watched a guy recap a dead inverter ckt that brought it back to life.


I worked on a lot of SMPSs as a tech in the 70,80/90s
The good ones had great overvoltage/overcurrent protection circuits.
I remember TVs coming into the shop "squealing" from the chassis and NP/NS. The horizontal output transistor would be shorted and the power supply would be trying to feed 140V into a dead short. It would switch on/off so fast it squealed high pitch. Replace the shorted h/out transistor plus any other failed components and the power supply worked great.

Other SMPS designs blew up almost instantaneously if you had a fault. They were great regulators but poor "forgivers'
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Originally Posted By: Papa Bear
Originally Posted By: sleddriver
Watched a guy recap a dead inverter ckt that brought it back to life.


I worked on a lot of SMPSs as a tech in the 70,80/90s
The good ones had great overvoltage/overcurrent protection circuits.
I remember TVs coming into the shop "squealing" from the chassis and NP/NS. The horizontal output transistor would be shorted and the power supply would be trying to feed 140V into a dead short. It would switch on/off so fast it squealed high pitch. Replace the shorted h/out transistor plus any other failed components and the power supply worked great.

Other SMPS designs blew up almost instantaneously if you had a fault. They were great regulators but poor "forgivers'
56.gif




Reminds me of the fax machine at home that would not start up after I unplugged it and moved it. I thought the MOSFET transistors
may be blown or the switching diodes went bad, but it was not that at all.

The PS board had lots of small electrolytic caps, 50uF 25V, etc, these were non low_ESR caps, turned out from being left on
for 15 yrs, the little bit of heat generated in the machine slowly dried out the caps and their capacitance dropped from 50uF to
5 to 10uF and the PS would not restart when plugged back in! $2 of parts and I was good for another 15 yrs!
None of the bad caps were bulged though !! The big caps looked OK!

There's just no repair shops you can pay to catch that kind of thing!
smile.gif
 
The trick set-up for checking electrolytic capacitors for value and leakage (resistance) is a curve tracer.
A curve tracer and a can of freeze spray will find a lot of intermittent and nuisance problems.
The curve tracer works well checking diodes & transistors for leakage.
https://www.youtube.com/watch?v=Gwo3pEH7hUE

My curve tracer used a decade box to select the range (not an octopus
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)
 
I've watched a many of W2AEW's videos. Great work & explanations. Wish I had more time to devote to playing with electronics like he does. I always enjoy it.

Spent a few hrs yesterday picking out low-esr AEC's and a solid for my project. I have another Pan DVD recorder that I want to view the board for any failing caps before I place my order.

It's always something......
 
I was expecting the new parts today however no joy. Odd that...ground is usually next day here in Tx. It was shipped FedEx. Tracking says Fri. afternoon. Plenty of rain here so good indoor project.
 
Back around 2004 the market was flooded with caps that couldn't handle the job. It didn't matter what brand, they all used them.Computer motherboards also had them.I worked with high end broadcast audio and video equipment and it was common to change 100+ surface mount electrolytics in a high end piece . Those didn't bulge, you either checked them or just replace them all. The thru hole ones would bulge out on the top. If you change out the bulged ones, it likely would resolve your issues. I wouldn't worry about the non bulging ones right now.
 
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Unfortunately re-capping wasn't the total solution. Upon plug-in, the unit was still dead. Further inquiry revealed that the main SWIC had also died. Upon replacing it from another unit, the piece now lights however it's stuck in a WAITING state.

I checked rail voltages and discovered one either being pulled low or another defective SWIC. This is a very complex smps and I'm having to quickly catch-up in their operation and troubleshooting. Needless to say, it's been an education! I also had to clear the entire bench just to make room for a single project!
 
Surprising that there are no Panasonic/Matsushita-made caps in that(or from the major Japanese capacitor suppliers like Rubycon/Nichicon/Nippon-Chemicon), but that could also been made by a 3rd party like Funai/Foxconn or a Chinese ODM for Panasonic.

Panasonic/Rubycon/Nichicon/Chemicon doesn't make all their caps in Japan - I'd still trust their Chinese/Malaysian/Indonesian/Taiwanese ones. However, the Japanese also had the same issue happen to them when they tweaked their electrolyte formula in the 1990s. Recapping ECMs is a common thing with the Lexus/Supra/DSM guys. In that case, you only want to use high-temp/long-life/low ESR caps from the major suppliers - Panasonic is preferred.

Bad caps/Taiwanese capacitor syndrome still happens today even with newer electronics. The motherboard suppliers now have to tout Japanese capacitors because of what happened 14 years ago.
 
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originals were elna.
not common but not junk.
electrolytic caps are the most perishable part in any device.
and this is an older unit that was likely on 24/7/365 running hot for many years.
cap failure is the most likely failure here.no matter what brand/series were used.
the whoflungdung china caps just die right outside of warrenty.
 
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