Compaq motherboard P5RC-LE

[silvergoat]

Looking for some replacement caps for this motherboard. I don't know what brand the current caps are, but I do know that at least a few of the different caps have gone bad.

The caps are brown and have a 3 line (form triangles) pattern on the top. They read KZG on the side where the voltage and capacitance rating is.

These are the markings on each individual type of capacitor I pulled.

[size = 10x25]
KZG
6.3v
3300uF
side = (M)105, 5(T), Dd

[size = 8x20]
KZG
16v
1000uF
side = (M)105, 5(T), DH

[size = 8x12]
KZG
6.3v
820uF
side = (M)105, G(k), 3A

[size = 8x8]
TMV
4v
680uF
side = 105

I found some that look like I could use them from Mouser, but I'm not sure that they are compatible because of other details like ESR and ripple.

http://www.mouser.com/Search/Product...47-UHM0J821MPD

http://www.mouser.com/Search/Product...47-UHZ0J332MPM

http://www.mouser.com/Search/Product...7-UHM1C102MPD6

I did not find any of the small 8x8 caps.

[t.j.]

http://kyxk.net/bbsanc.php?path=%2Fg...0544.v0&ap=553

united chem con is what ya got! cheapos! link hs dat sheet so ya can compare, also try digikey!

[mariushm]

They're by no means "cheapos" just a series that had manufacturing flaws and eventually the capacitors in that series are going bad, often without showing any signs of failure.

I think TMV may have the same issue.

Replace with Nichicon HN/HZ ... HM should also work... yeah, the links look good to me.

[silvergoat]

Digikey is one alternative to mouser- are there any others I may look at for future reference?

[c_hegge]

^
Yup. There's Badcaps.net

btw, the 680uF TMVs should be replaced with 560uF polies ( http://www.badcaps.net/store/product...products_id=79 ). Also fill up any blank spaces with them.

[silvergoat]

Not too expensive to do this, and it may be worth it for the extra practice.....hope it doesn't explode when I power it up.

[Uranium-235]

it might...if you don't know about this...this board was made by asus, and the pictures I see of it have the polarity marker (half moon) on the POSITIVE side. So when you put the caps in, make sure the negative marker is on the empty side of the board marking, not the full one. Just look around your current caps, you should see the marker line (going from top to bottom) on the empty side of the circle marking. If you put it on the full side of the circle (how most motherboards are setup), you'll actually be putting it in reverse, and it will blow your replacements the second you turn it on

that said, ask around about desolering techniques if you're new to this

[silvergoat]

Desoldering and cleaning up the holes has been the most difficult part of all this.

I tried adding solder to the joint so that I could use my soldapullt, but the solder does not adhere to the joint and instead goes right over it to the iron. I've been using no-clean flux, but it doesn't really help other than make a sticky mess. The only thing that really works is getting the iron up to almost 700 degrees (~450C), and then it makes it a whole lot easier. I'm not sure if I'm supposed to use higher heat to desolder, but it does the trick, unfortunately it took me over half of the capacitors I pulled to figure that out.

Also, what kind of grease to help with the seal for the soldapullt?

Any other tips?

[Uranium-235]

I use this

http://www.mgchemicals.com/products/8341.html

keep the iron at about ~500-550 or so and clean it off, and put some leaded solder on it, and TOUCH it to the flux wetted joint (preferably using a chisel tip) for a few seconds, the flux should let it transfer to the joint easier

[silvergoat]

Are you talking about 500+ degrees Celsius, or Farenheit? I am using Kester 44 (RMA) 63/37 .031. I also ordered a roll of the Kester 44 (RA) 63/37 .020 to see if I have better luck with that at slightly lower temps.

I always keep my tip tinned, almost non-stop if it's idle, but I'm still seeing a lot of brown liquid pooling on the tip until I get it into the brass, mostly when I go above 400C.

I use a Hakko FX888 (IIRC) with a 1.6mm chisel tip. I also have a 2.0, 2.4, and 3.2 in case I need to retain more heat with other stuff. What is recommended for a mobo?

I thought I had all the bases covered, but if I have to get better flux, or scrub the surface a little than I need to be a little better informed on identifying problems and locating the correct solution.

Thanks for your help in this Uranium-235......

[Uranium-235]

I would use the 3.2. I think I use about a 2.8 but I never measured it. If you're worried use the 2.4

if the 'brown liquid' is what I think you're talking about its probaly the rosin itself, its normal

you can't use a thin tip for through-hole stuff except in specific cases

I was talking about 500F, I have a weller WESD51 and haver NEVER had to turn it past 700F, if I remember correctly I last had it about 600, but don't quote me on that its in storage right now

[silvergoat]

Thanks for the advice- I will give it a try with the rest of the capacitors.

What is the reason for going with the bigger soldering tip vs the smaller soldering tip? What are the thinner tips for?

[Uranium-235]

on occasion, certain SMD stuff

a thicker tip allows for more surface contact and heats it up faster