Blown Capacitors (?) in a TV Digital Video Recorder

[RonMig]

No it's not a mig welder, but has internals with some similar components, to the untrained-eye (me).
It is a Humax PVR9300T, quite old (15yrs?) but functional until a few days ago.
It now just stays on standby; tries to power-up when directed but then gives up after about 20 seconds & goes back to standby.
Just cleaned the dust out and looks like 5 or 6 capacitors might be leaking - could this explain the inability to power-up?

I'm not exactly electrical-minded, but willing to do some soldering if our resident electrics-wizards think its worth trying?
Where's the best place to search, any recommended makes etc?
Should I only replace the dodgy-looking ones, or the other same-ones too?
I need even the basic help, like, point me at the actual ones to buy, as my eyes and brain glass-over and words go over my head with electrics-tekkie stuff.

a few piccies -

The leaky ones all say Sam Young NXB 10v 220uf.

As far as I can tell, the hard-drive is fine, can hear it spinning up, but if it's not the capacitors I've got no ideas...

thanks in advance

Ron

 

[carbon]

Capacitor’s need replacing. They don’t have to be the same make but same capacitance values and ideally same temp rating. If you can’t find them with the same voltage rating you can replace them with higher voltage rated ones.

 

[voipio]

Those caps are definitely worth replacing. I bought a capacitor kit from Maplins years ago, and used those to recap a NAD amplifier, a graphics card, and a couple of other things, giving them a new lease of life. It may have been this kit:

https://cpc.farnell.com/velleman-sa/k-cap2/electrolytic-capacitor-kit-120pc/dp/CA08364

The other thing to do is measure the power supply output voltages at the multiway connector right next to one of your leaky caps.

 

[RonMig]

Ok, thanks for your replies and for the farnells link.

I like the £15 multipack concept, I'm not going to quibble over the pennies, just want to find the right ones.

I also remembered the name rs components from a previous (mig-repair) thread, and found these, which has a minimum order value so would give me 100 items for £6.20 plus postage.... is this the right one? https://uk.rs-online.com/web/p/aluminium-capacitors/7110808

I've read they only work fitted one-way - are they or the board marked to show which is the right way?
Not sure about measuring output volts, I have a multimeter but have only ever used it for checking 12v car batteries.

Not confident here - have managed to get mains-shocked a few times in years gone by so makes me very wary....

 

[carbon]

The rs ones are the correct items and the board will likely be marked but check before removing all the capacitor’s or take some detailed pictures before starting work on it

 

[MoreWellie]

These would be ok https://cpc.farnell.com/panasonic/eca1cm221/capacitor-220uf-16v/dp/CA07278 for the ones shown, or https://www.ebay.co.uk/itm/284294395892

Not sure if all leaking are the same 220uf so you need to check all leaking capacitors before ordering in case some are different values

I've read they only work fitted one-way

Correct, the grey band on the ones in your picture show which side is the negative lead and you should fit the replacements with the + and - in the correct positions

Easiest to do one at a time

 

[RonMig]

These would be ok https://cpc.farnell.com/panasonic/eca1cm221/capacitor-220uf-16v/dp/CA07278 for the ones shown, or https://www.ebay.co.uk/itm/284294395892

Not sure if all leaking are the same 220uf so you need to check all leaking capacitors before ordering in case some are different values


Correct, the grey band on the ones in your picture show which side is the negative lead and you should fit the replacements with the + and - in the correct positions

Easiest to do one at a time

haha thanks - now you've said this, I can see the + sign on the board opposite to the grey stripe with the "-" on it how did I not see that ?
like I said, my eyes and brain glass-over...

 

[droopsnoot]

I had a similar issue on my old Vestel PVR - it was a common fault on those. Despite picking up another (differently branded - Vestel made them for loads of people) on the car boot sale for a couple of quid, it was very satisfying to be able to fix them with some new capacitors. On mine, I think something took out a diode or resistor elsewhere on the board, too. Fortunately someone had documented the fix, as I'd never have worked that out for myself.

 

[Ross365]

Those caps have burst, which is typical of what happens when they've seen too high a voltage, so they may be a symptom rather than the underlying cause. You can probably get higher voltage components (25V ?) that will fit physically. I think I'd look for Panasonic components off eBay.

It might be a good approach to cut one out and measure the voltage across the connections; I'd guess it should be 5V, but if it's more than 10V that tells you that there are other problems which really need sorting first.

 

[Ross365]

Thinking about it some more, really, all the burst ones need cutting out together. If any of them them has shorted internally, the voltage will be zero, and you really need to know what it is without any shorts on the line.

 

[pedrobedro]

Clip the legs with toenail clippers and desolder them and mark the board with a Sharpie where the grey band negative goes. I replaced a couple in a motherboard and resurrected it. Lasted till it was obsolete.

 

[Alan Reynolds]

Sam Young have a history of underrated capacitors. Apple had a similar problem on their motherboards.

 

[voipio]

Thinking about it some more, really, all the burst ones need cutting out together. If any of them them has shorted internally, the voltage will be zero, and you really need to know what it is without any shorts on the line.

Capacitor rot, or plague, is quite an issue with electronics gear from a certain era:

Capacitor plague - Wikipedia

en.wikipedia.org

The capacitors affected tend to lose capacitance, so basically become open circuit, rather than short. Power supplies tend to cease to function, and power supply rails become very noisy, leading to more and more data glitches before the circuit fails completely.

 

[The_Yellow_Ardvark]

When DVR's are used in CCTV systems we used to see blown capacitors on the main boards when thgere was a power supply issue.
Either incoming or internal ones.
It was almost like, due to the lack of on board fuses or fuse wires they use the capacitors as protectors.

Most times the hard drive was undamaged. The cost of new ones made them almost a disposable item.

 

[Matchless]

These were the main component I used to replace inside BMW heater control panels and other units, they just swell up, fixed the problem 9 out of 10 times, 20p turned into £50.00, happy days....

 

[RonMig]

I cut out the 6 leaky capacitors, they're all same 10v 220uf.
Tested the board connections for each one and got volts as shown in piccy below.

Switched-on and on standby, only nbr3 had a volt reading which did not change when activated.
The others were all zero on standby, went up to their figures when activated, then back to zero after about 25 seconds as it went back onto standby.

No idea if these values are likely to be within normal operating parameters (!) ?

I've ordered the suggested panasonic replacements, so will give an update in about a weeks time, depending on delivery service...

 

[MoreWellie]

Without having a circuit diagram or another good machine it isn't possible to know what the expected voltages should be

At least all yours are well under 10v so you should be fine with the 16v Panasonic capacitors

 

[Ross365]

It was really lucky for you that all those caps were soldered in such that you could easily cut the leads! They are often mounted right down on the board with no leads visible, so then you have unsolder them from the board, or grit your teeth and pull them off the top, hoping they will leave the connector wires in the board.

 

[RonMig]

One thing surprised me about capacitors when reviewing adverts-
- they are listed as having what looks to me like a quite short life expectancy, ranging between 1000 to 5000 hours depending on make etc...
Our tv recorder is on virtually 24/7, rarely on standby - so even at 5000 hours, that's less than 12 months use before they could fail.
The unit is 15+ years old so I'm not complaining, just seems odd.
Maybe the capacitors power-down more than I'm aware of, independent to the standby function...?

 

[RonMig]

It was really lucky for you that all those caps were soldered in such that you could easily cut the leads! They are often mounted right down on the board with no leads visible, so then you have unsolder them from the board, or grit your teeth and pull them off the top, hoping they will leave the connector wires in the board.

Agreed, although I could only just get the snips in those gaps.
The wires were closer-together than the holes, so were splayed out then down & making a little buffer-zone for me