Electronic Components

[Sparkshower]

so i ordered some components from ali-express, blue disk shaped capacitors. Looking it up i find they are ceramic capacitors so i get the numbers form the old one (103M 1KV 19W), order them, wait, then today they came in the mail.
Well they look a bit different

It just doesn't look right i don't think technology has progressed that much since this TV was made, where did i go wrong?

 

[rjenkinsgb]

The TDK ones Mouser sell have 7.5mm lead spacing and look very similar.
Is it thicker than the original one? It could be multilayer rather than single layer.

Or, something to do with the pulse current rating??
(Or it's possible they are dodgy, but it does not seem unreasonable to me).

The PCB has holes to take two different size components.

 

[Nigel Goodwin]

Should be no problem, going back years I replaced countless ones in TV's etc. and new ones were often much smaller. However, with Chinese suppliers there's always the risk that they could be fake ones? - regardless of size.

Notice the PCB even has hole spacing for that size of capacitor.

 

[Tony Stewart]

I expect a difference in ESR and thus ripple attenuation but depends on circuit impedance, BW. V rating depends on ceramic quality for contaminants and gap, C depends on area/gap ratio. Only testing can verify.

 

[MrAl]

The hole spacing may not have anything to do with the different size cap, based on size alone. It could be that the smaller spacing was for capacitors of a different value/rating used in a different model that uses the same PC board.

 

[Nigel Goodwin]

The hole spacing may not have anything to do with the different size cap, based on size alone. It could be that the smaller spacing was for capacitors of a different value/rating used in a different model that uses the same PC board.

Almost certainly not, it's quite common for PCB's to have three holes in order to accommodate different size capacitors. Those small blue HV capacitors are a common failure, and from new they can have either physic size fitted - which makes it easier to fit either size as a replacement.

 

[Sparkshower]

Im used to replacing components with things that look the same the ones i looked up on digikey just now are the same physical size. If i put in the curcuit and test it? If its not right it will just blow straight away as it has done with the previous component? Now it got me thinking why it blew in the first place brown out? Lightning strike? Bad component?

 

[Sparkshower]

The TDK ones Mouser sell have 7.5mm lead spacing and look very similar.
Is it thicker than the original one? It could be multilayer rather than single layer.

Or, something to do with the pulse current rating??
(Or it's possible they are dodgy, but it does not seem unreasonable to me).

The PCB has holes to take two different size components.

They are about the same thickness

 

[Nigel Goodwin]

Im used to replacing components with things that look the same the ones i looked up on digikey just now are the same physical size. If i put in the curcuit and test it? If its not right it will just blow straight away as it has done with the previous component? Now it got me thinking why it blew in the first place brown out? Lightning strike? Bad component?

As I mentioned in post #5, those capacitors are a VERY common failure - they usually have obvious splits, cracks, black spots, or even blown completely to pieces. Nothing causes it, it's just capacitor failure, it's high voltage, it's under considerable stress.

In almost all cases, simply replacing the capacitor (and possibly a blown fuse/resistor?) is all that's required.

The capacitors themselves were always fairly difficult to source, so I used to have a draw full at work with all the different values I could source from TV spares companies.

 

[MrAl]

Almost certainly not, it's quite common for PCB's to have three holes in order to accommodate different size capacitors. Those small blue HV capacitors are a common failure, and from new they can have either physic size fitted - which makes it easier to fit either size as a replacement.

Here's what I said:
"The hole spacing may not have anything to do with the different size cap"

Note the word, "may" in the phrase "may not".
I said that because I have seen boards used for more than one product. It was to save money on the manufacture of boards when a company made more than one product that were similar but had different features. Often the next model up would be more expensive.

 

[Sparkshower]

I expect a difference in ESR and thus ripple attenuation but depends on circuit impedance, BW. V rating depends on ceramic quality for contaminants and gap, C depends on area/gap ratio. Only testing can verify.

Would measureing the resistance of the new one and taking a similar one to the blown one out of the curcuit and measuring that be sufficient?

 

[Nigel Goodwin]

Would measureing the resistance of the new one and taking a similar one to the blown one out of the curcuit and measuring that be sufficient?

You can't measure the resistance of a capacitor, and ESR only really applies to electrolytics - as I've already explained, the capacitors are perfectly interchangeable, and would have had either fitted (depending which was available) during original manufacture.

You're over thinking this, just change it

 

[Tony Stewart]

You can't measure the resistance of a capacitor, and ESR only really applies to electrolytics - as I've already explained, the capacitors are perfectly interchangeable, and would have had either fitted (depending which was available) during original manufacture.

These MLCC general purpose caps are usually X7R for 0.01uF/ 0.1uF and are usually Class2 = 2.5% measured at 1kHz
DF is a ratio of ESR to X(f) and is the cause of any heat damage.

DF=2.5% is less than most e-caps

They are small due to the multi-layer SMD chip fit between welded leads.

only CoG ceramics are low ESR. DF=0.1% @ 1MHz.

 

[MrAl]

Would measureing the resistance of the new one and taking a similar one to the blown one out of the curcuit and measuring that be sufficient?

Hi,

Look up the dissipation factor or loss tangent and see if you really want to be bothered by that kind of measurement, or just change out the capacitor like Nigel suggested. I'd just change out the cap. If you are worried about the size difference than just go with the same size cap.

Just for a little background info...
One of the biggest problems with caps is the voltage rating. The voltage rating should be a bit greater than the actual voltage present. How much higher depends on different factors. For example, I think a 16v rated cap is not a good choice for automobiles with a 12v battery system because the charging voltage can get close to 15v in some cars. That's too close. a 25v rating would be much better.
The other problem in some applications is ripple current. Ripple current can cause a lot of heating where the cap actually gets hot. It can actually explode. In these cases the solution is to use a cap with a higher ripple current rating or use more than one cap in parallel.

 

[Nigel Goodwin]

Hi,

Look up the dissipation factor or loss tangent and see if you really want to be bothered by that kind of measurement, or just change out the capacitor like Nigel suggested. I'd just change out the cap. If you are worried about the size difference than just go with the same size cap.

Just for a little background info...
One of the biggest problems with caps is the voltage rating. The voltage rating should be a bit greater than the actual voltage present. How much higher depends on different factors. For example, I think a 16v rated cap is not a good choice for automobiles with a 12v battery system because the charging voltage can get close to 15v in some cars. That's too close. a 25v rating would be much better.
The other problem in some applications is ripple current. Ripple current can cause a lot of heating where the cap actually gets hot. It can actually explode. In these cases the solution is to use a cap with a higher ripple current rating or use more than one cap in parallel.

These capacitors are generally used in switch-mode PSU's (as snubber components), or in line output stages in CRT TV's - in both cases they are subject to high voltage pulses. Hence their rating of 1000V - many of the replacements I used to stock were rated at 2000V, regardless of their physical size - although it was random chance what physical size, and what voltage, arrived after ordering them. Funnily enough, most 2000V ones were the smaller size, presumably the smaller caps were a later variation?.

 

[MrAl]

These capacitors are generally used in switch-mode PSU's (as snubber components), or in line output stages in CRT TV's - in both cases they are subject to high voltage pulses. Hence their rating of 1000V - many of the replacements I used to stock were rated at 2000V, regardless of their physical size - although it was random chance what physical size, and what voltage, arrived after ordering them. Funnily enough, most 2000V ones were the smaller size, presumably the smaller caps were a later variation?.

Oh that's very interesting. I have to wonder if they cut corners to get a smaller size, or maybe just better dielectric or something. Maybe a test would be worth it then just to see what comes out of it. Could they even be better than the older style.

 

[Nigel Goodwin]

Oh that's very interesting. I have to wonder if they cut corners to get a smaller size, or maybe just better dielectric or something. Maybe a test would be worth it then just to see what comes out of it. Could they even be better than the older style.

Fairly obviously, I've changed a LOT more of the larger ones when they failed, but that's probably simply because they were in use years before the smaller ones - but I've not got enough evidence to suggest one type might be better than the other.

From an engineers point of view, they were a nice simple fix - as any engineers knows, eyes first, hands last - during your initial visual inspection look out for any small blue disc capacitors, if you spot any (they are in obvious places) check for cracks or black spots. If they have cracks or burns, then replace them - job done - it's fairly rare for anything else to fail, although a fuse or surge limiter did occasionally.

 

[Sparkshower]

I ended up just changing it and the tv works thanks for your help guys

 

[Nigel Goodwin]

Could have done it last Tuesday

But well done.

 

[Sparkshower]

Could have done it last Tuesday

But well done.

Yeah first time for me changing individual components as opposed to buying a new power board the difference in old and new threw me off