capacitor

[M0BSW]

I know this is probably  a numptyquestion  before you shoot me down in flames, I have a circuit that states the capacitor needed is a 3p3, I can't make up my mine is that 3.3 pf or 33pf, I think it 3.3 any way I'm totally buggered with this ,any help would be appreciated  I'll just duck under the parapet  and  raise the white flag

[Zbig]

Yup, that's 3.3pF. It's a common practice used in order to avoid mistakes or ambiguity due to misprinted decimal points, etc.

[M0BSW]

Yup, that's 3.3pF. It's a common practice used in order to avoid mistakes or ambiguity due to misprinted decimal points, etc.

Thanks Zbig, I was pretty sure but not a 100% ,thanks for replying
Paul

[Zero999]

Be careful with the circuit layout. The fact it requires such a low value capacitor, implies it's running at a high frequency or there's a high impedance/low current so parasitic capacitance and inductance could be a problem if it's just slapped together with long leads/circuit traces.

[M0BSW]

Be careful with the circuit layout. The fact it requires such a low value capacitor, implies it's running at a high frequency or there's a high impedance/low current so parasitic capacitance and inductance could be a problem if it's just slapped together with long leads/circuit traces.

It's an RF Sweep Generator, and I am keeping everything tight, also I'm shielding parts of it too, it's going in a metal enclosure, where I usually use plastic, thank you for the interest.

[M0BSW]

Be careful with the circuit layout. The fact it requires such a low value capacitor, implies it's running at a high frequency or there's a high impedance/low current so parasitic capacitance and inductance could be a problem if it's just slapped together with long leads/circuit traces.

It's an RF Sweep Generator, and I am keeping everything tight, also I'm shielding parts of it too, it's going in a metal enclosure, where I usually use plastic, thank you for the interest.

PS I'm also going to try a twisted wire  capacitor I have made and pruned down to 3p3, just to see the effect and if it works OK it will stay, I remember Fender use to use some twisted wire capacitors in their amps.

[LeWidget]

Hey guys,

I have a circuit board here with a capacitor rated at 10v 100µF 105°C that needs replacing. I was planning on using http://australia.rs-online.com/web/p/products/2286650/ but then realised its Max operating temp was 85°C. I then came across http://australia.rs-online.com/web/p/products/5193949/

Just wondering, should I stick with the same temperature ?

The caps are from a little wireless speaker set for my PC that I'm fixing. http://forums.logitech.com/t5/Speakers/z-5450-rear-speaker-troubleshooting/td-p/283634/page/2

Regards,

[mariush]

No, you shouldn't replace it with a 85c rated capacitors. Those are usually general purpose capacitors, with just average technical characteristics.
In that thread you linked to, I see a picture in which it seems there's a switching power supply. Switching power supplies require capacitors of higher quality, in general.

The 10v is only the maximum voltage the capacitor can handle before getting damaged. Therefore, you can often replace an existing capacitor with one rated for higher voltage without any problems. In your case, you could go for a 16v or 25v rated capacitor.

I would recommend going with these:

http://australia.rs-online.com/web/p/aluminium-capacitors/4491040/
http://australia.rs-online.com/web/p/aluminium-capacitors/7497149/
http://australia.rs-online.com/web/p/aluminium-capacitors/0571874/

[LeWidget]

Thanks Mariush

Is there any pros / cons to going to a much higher voltage capacitor? ie. 10v > 25v ?

Regards,

[AKM]

@LeWidget
Only con is the slightly higher price; but a few cents shouldn`t be an issue for a repair.

[LeWidget]

Thanks AKM I went ahead and ordered some 16v caps from Rubycon

Thanks again,

[LeWidget]

Hey guys

Have another coupe of situation,

I replaced the capacitors int he speakers as above, but the control pod for the Z-5450 system seems to power into Stand-by, but when trying to power on (power button), it lights blue (as it should) but for 1sec, then shuts-off for a few seconds, then powers back into stand-by. The capacitors in the control pod are all 'CapXon' brand, someone said they were crap, they were also the ones replaced from above post(s).
Unfortunately I don't have an ESR meter to properly test if these are bad, so I was planning on ordering a heap of replacement capacitors of equal value from farnell (element14) and just replacing them.. thoughts?







----------------------------------------------------------------------------------------------------------------

Problem #2 - Xbox 360 RROD

I had a xbox 360 with rrod, I opened it up to find some caps not looking so well. They also happen to be 'Rubycon' brand too. Not sure if they overheated on there own or from the other ship.. but they look a lil' burnt.





I was just gonna replace the 4x with http://au.element14.com/rubycon/6-3zlj2700m10x20/cap-alu-elec-2700uf-6-3v-rad/dp/2346438 (add em' to my cart with the other stuff)

Not sure if they're totally stuffed.. but replacing them just in-case.

There's a couple of other caps starting (very little) swell.. but not sure if they too are like that from overheating or not.

I'd like to get an ESR meter, but they're a bit costly for me at the moment (no income). I was looking at the Bob Parker one, I hear it's good.

Thoughts?

Thanks guys, much appreciated  

[PedroDaGr8]

I cant speak to question one


Q2: Those caps look like they are toast. Heat is the #1 enemy of electrolytic capacitors and look what they are located directly next to. Even the best capacitors will fail when heated. I would say you are safe replacing all of them. The brown color is from the internal electrolyte that has spilled out. It's smelly stuff (often described as smelling like cat piss).

As for the ESR meter. The Bob Parker meter was a great device when it came out a decade or two ago. Nothing did what it did at that price point. These days the game has changed. The BP meter runs around $100 and at that price you can easily get a fully featured LCR meter; specifically the DE-5000 meter by Der EE. On eBay you can get that meter with the optional alligator clips and the SMD tweezers for just a tad under $100 shipped.

[mariush]

In the case of question 1, I would CAREFULLY remove all that dark yellow, brownish glue that's all over the board. Be careful not to rip surface mount resistors and capacitors when you try to peel off that glue.
The brown stuff could be a type of glue/elastic goop with a bad chemical formula. It was used/supposed to prevent vibrations of parts and keep the parts on board when soldered automatically by a machine. However, some of those glues/chemicals however had a bad compositions which made them conductive as they dried out (due to heat and long time) so now some components could be shorted or have different resistor values under that stuff.

Also, when testing anything, first thing you do is check voltages. Make sure the board has proper voltages, that the chips have good voltages etc etc A lot of the chips on those boards have the product name on them (for example i see a NJW something), you can get the datasheet for those chips, look at the pinout to see which pin is voltage, which is ground, then see what voltages is that chip supposed to work at and measure the voltage on the chip to make sure the board has some voltage there.