Remove CMOS battery? Does it matter?

[SheDevil]

I removed all other parts, but did not even think about the little battery there before I started the de-soldering. As I get to the 3rd to the last smaller crap, I noticed it is by the battery.

Should I have removed it? In not doing so will that damage something?

Can I test the caps with a digital volt meter that reads megohms to .001? Some are above that, but the new caps are in that range .006>.001 or does that special ESR meter do something else in testing them? The megohms on some of the swollen ones were above 3.000

In testing the volts on the old ones I found a few that with the leads on correct + and -, it reads a negative voltage. Is that another indication that one was on its way out?


Soltek 75DRV-5
GSC Caps
Enermax EG365P-VE
next step is to look at PSU while it is torn apart.

Thanks, hopefully another board saved.
Shedevil

[MD Willington]

Re: Remove CMOS battery? Does it matter?

Batteries are ~$5 for a dual pack at walmart (Sony, Panasonic or Energizer CR2032)...I'd just buy a new battery...

[Rainbow]

Re: Remove CMOS battery? Does it matter?

Personally, I don't remove the battery when soldering the caps (or anything other not related to CMOS power). But I take care not to short it out (the easiest way to destroy the battery is to put the board on metal surface). I never buy new batteries as I sometimes get boards that are unrepairable but the battery is often good

[willawake]

Re: Remove CMOS battery? Does it matter?

what is the brand of multimeter, it sounds interesting.

it would be best to check the caps when the board is working using an oscilloscope.

can read this about esr
http://www.repairfaq.org/sam/captest.htm

[AK0R]

Re: Remove CMOS battery? Does it matter?

Can I test the caps with a digital volt meter that reads megohms to .001? Some are above that, but the new caps are in that range .006>.001 or does that special ESR meter do something else in testing them? The megohms on some of the swollen ones were above 3.000
Shedevil

No. Digital voltmeters measure resistance with a DC voltage. ESR is measured with an AC voltage. To truly compare apples to apples, you need to know the frequency used by the manufacturer in specifying the part. Also, .001-.006 on a 1 megohm scale equates to 1000-6000 ohms, which tells you nothing about the quality of the capacitors. ESR on good electrolytic capacitors is much less than 1 ohm.

[Rainbow]

Re: Remove CMOS battery? Does it matter?

You're basically testing the capacitance - the bad caps get charged by the meter (as they have often very decreased capacitance, not only high ESR) and so they "look" like a higher value resistor to the meter.
I've tested this on some bad caps and meter set to 2M ohms - all caps that showed higher resistance were bad (bulged). But it does not work the other way - some were bulged but the resistance was still "OK".

[SheDevil]

Re: Remove CMOS battery? Does it matter?

Thank You to all, what a task.
I was trying to look for a way to test the new ones to double check. I DO NOT want to do this again anytime soon! coffee and soldering don't mix sometimes. good thing I am very detail oriented and have patience. I just know that sometimes even new things can be faulty.
I suppose I could call around to see if any local tv-radio repair shop would test them for me.

Would they be able to tell me if the new caps were all good, weed out any weak ones?

They are Nichicon HE series I bought them from Mouser online. I got that HE series because the size matched better than the PW.
PW 1000uf 6.3v .068 Impd 755 ripple 10x12.5mm
HE 1000uf 6.3v .087 Impd 840 ripple 8x15mm

I'll be ready for them to laugh at me too. One guy told me he would not do what I am doing in a million years and kind of laughed at me like I was stupid for even trying. Then what the #$%@ are your doing in the repair business I felt like saying. We repair pools and spa and I would never think of using that approach he did with me on the phone.

So if the solder sucks down into the hole, and I have a nice shiny cone with no spikes, is that a good indication that the solder joint fills the hole to the other side? I put just a small tick of flux in the hole, does that help make a better solder joint?
I'm using the 62/36/2, only one in the .022 size.

I just found that when I put a little flux on the solder braid it sucked up onto the braid better.

Shedevil

[willawake]

Re: Remove CMOS battery? Does it matter?

i dont bother testing the new ones, i just use them and if the board is not passing memory tests or stress tests then i guess i would look into testing. but it has not happened, the majority of the boards/devices are still working perfectly and the asus board i screwed up i know was due to excessive heating.

i never did get around to getting a cheap scope like KC8 recommended and learning to use it. It is a good idea though because you are testing the circuit as it is working and seeing how the old caps/new caps are performing.

it is not necessary to put flux in the hole, i just use 60/40 0.8mm, heat up the lead and solder pad at the same time and close the hole with solder. no need to make the solder fill the hole through to the other side, the lead port is connecting the solder pads on the front and back of the board and making the connection to the right traces in the board layers.