Electrolytic capacitor / SMD question!

[Moreno83]

Hey guys ,

Normally i post in the tv section but i have a few questions about those small smd capacitors and "normal" capacitors.

First question is , whats the difference between the electrolytic capacitors with a black colour showing the negative side and a red colour?

Also , on most power supply's in televisions you have the hot and cold side. On the cold side i have a few 1500uf/25v that i want to replace but sometimes i read about low esr. I normally just purchase capacitors with same value and higher voltage and don't pay any attention to low or high esr.

Is it save to replace the 1500uf for example 1800/25v or 2200uf/50v?

What can possibly go wrong? Can those caps pull down for example the 5VSTB?

[Moreno83]

Re: Electrolytic capacitor / SMD question!

These caps! They have weird values also , 120uf.

[stj]

Re: Electrolytic capacitor / SMD question!

red print may be polymer caps.

on the output of psu's you should keep the voltage the same, keep the uf's the same or slightly higher, but use low esr caps only.
unless you want the new ones destroyed pretty quickly.

[Moreno83]

Re: Electrolytic capacitor / SMD question!

Thanks for the reply!

[Behemot]

Re: Electrolytic capacitor / SMD question!

You can go down with voltage as long as you know it's safe. They often use much higher voltage most likely because tho cheap craps can not actually withstand rated. So for example 25V cap on +12 V rail - pretty safe to use quality 16V caps in there. And increase the capacitance on the other hand.

Capacities like 120 uF are actually common if caps are miniaturized but not so much to jump on the next more standardized capacity. Check those new Chemi-Con KYA, KYB, KZN, KZM, KZH series, they all have these 120, 39, 80, 270 uF etc.

[Moreno83]

Re: Electrolytic capacitor / SMD question!

Thanks for the reply , great info!

[Stefan Payne]

Re: Electrolytic capacitor / SMD question!

They often use much higher voltage most likely because tho cheap craps can not actually withstand rated. So for example 25V cap on +12 V rail - pretty safe to use quality 16V caps in there. And increase the capacitance on the other hand.

...or higher ripple current, lower impedance or they use 25V caps due to some other things we don't know about but the engineer thought about when specifying those for that...

So I always would replace a 25V cap with at least a 25V cap, even on +12V rails...

[Behemot]

Re: Electrolytic capacitor / SMD question!

Oh my…

[mariushm]

Re: Electrolytic capacitor / SMD question!

In all likelihood, they used 100uF 25v capacitors because the diameter of 100uF 16v and 100uF 25v were the same, or they used 100uF 25v somewhere else on the board (so saving money by ordering more of same part and saving a roll on the chip shooter machine), or the cost for both versions was the same.

In the picture, it looks like there was some height constraint, so they used several capacitors of smaller capacitance in parallel to obtain the value needed.