Can I replace 6.3v 1800uf caps with 6.3v 1500uf?

[James198]

I have 5 capacitors that popped on my mobo, there 6.3v 1800uf. No computer shop around here has any. One guy looked on atleast 25mobo's he had and not one, all he had were ones that were 6.3v 1500uf.. Will they work or am i gonna have to buy some on ebay?

 

[raybay]

It is worth the time and money to get quality Caps made in Japan... buy them from a company that sells electronic goods... use the caps described for the job, unless your replace every one.

 

[captaincranky]

Using lower value capacitors in the voltage regulator circuit will possibly produce more ripple and less stable voltage than the proper value caps would.

With that being said, the caps in the circuit are probably about 10% tolerance. Which at most could be 1980 pfd or at minimum around 1620 pfd. So, the 1500's on the high side would be maybe 1650 pfd., and you're getting close.

However, if I had my druthers, I'd rather install the next size higher (capacitance NOT voltage), which would absolutely reduce ripple. Thid assumes of course, that they would fit in the holes provided.

The caps in the voltage regulator circuit merely serve as power filters, and as such, this is not truly a critical application.

Precision capacitors would more likely be found in an oscillator circuit, as in a frequency generator.

But, as raybay pointed out, my simple search for "computer electrolytic capacitors" returned 208.000 results in .24 seconds. If you decide to hit Google, be sure to add the terms, " solid electrolytic" and/or "Tantalum electrolytic" to the mix.

You also have to understand that the voltage regulators themselves may have been damaged when the caps blew. That said, this would be a possible fix, not a definite fix.

 

[DelJo63]

the difference 'twix 1800 & 1500 is insignificant in the PSU. If you're looking for reliability,
increase the voltage rating and ignore the UFD spec.

If the rail you are reparing is 5.0V, then get a voltage rating of at least 1.414 * 5.0 or == 7.0 v

the 1.414 value is the PEAK voltage from the RMS output.

(ps: I built mobile radios in my prior life)

 

[captaincranky]

the 1.414 value is the PEAK voltage from the RMS output.

(ps: I built mobile radios in my prior life)

So then you know that's zero to peak. not peak to peak from an AC source.

I love the number 2 and it's powers. If you take 1, then multiply it by 1.4, and multiply that by 1.4, and so on. you'll quickly see how the F stops on a camera lens come to be named. (Isn't it weird how the inverse square law and AC voltage measurement come to be intertwined)?

 

[DelJo63]

So then you know that's zero to peak. not peak to peak from an AC source.

correct :wave:

 

[raybay]

Good job, Captain Cranky.

 

[James198]

Thanks for your help!