Desoldering help

[Bostich]

I'm attempting to do the RGB mod for the NES, but I'm running into a few problems removing the original PPU.

I have a desoldering tool that works pretty well, about 75% of the time.  It's basically like a soldering iron with a hollow tip and it uses suction to remove the solder.  The problem is that sometimes the solder is down inside the holes and it seems to be nearly impossible to get out.

I was able to remove the original PPU, but a few of the holes are partially clogged.   I had tried a couple of things to get them cleaned out, but it wasn't really working all that well.  Basically what I was trying was to stick a thin piece of metal (chip pin, staple, etc.) in the hole and heat it.  The soldering iron I was using at the time has a rather large chisel tip so it was a little tricky.  I was able to get the solder to melt inside the hole, but I couldn't get it all cleaned out.

So then I had the idea that if I could find a soldering iron with a small enough tip I could just stick it inside the hole and push the solder out.  It seemed like a good idea to me at the time...

So I went to a local electronics store and found a $3 iron with a small conical tip.  It looks like about 0.8 mm or so.  They had smaller tips at the store, but they didn't look like they would fit the iron I already had nor would they fit the the cheap one I found.  So anyways, I bought the cheap iron and found that the tip is just small enough to fit a little ways inside the holes on the motherboard.  I thought, "Sweet, this just might work."

So I heat up the iron, stick it down inside the hole...what's that burning smell?!!  All inside the hole and just around it is all black now and it smells terrible.  I'm thinking it must be beyond hope of recovery now.

Sorry for the long backstory...my main question is--how do you remove solder from inside the pinholes without frying the board?

[TJ_Kat]

Desolder wick. Sucks it right up.

[benzaldehyde]

Hoo...

So I'm not alone in thinking the solder Nintendo used was a bitch with which to work. When I did that mod I had the same trouble. I'd follow TJ's suggestion and use a wick; you'll also need a hot iron. I used mine at 30 watts, but don't press down for too long. If the solder doesn't melt in a few seconds, remove the tip and try again. Don't worry about ruining the board; just take your time and you'll work it all out.

[phreak97]

if you have solder down inside a hole that wont come out, resolder the joint and start over. with that suction tip, put the tip over the fully soldered hole, leave it for a couple of seconds to melt all the way through, then activate the suction.

im working with these at tafe atm

[Bostich]

Thanks for the responses.  I think I will start by getting some desolder wick.  Are there any special precautions to follow when using desolder wick?  I have 2 soldering irons, one of which is a 20/40 watt switchable, the other is 30 watt.

The desoldering tool I have is only able to provide suction in a quick burst, so I'm thinking it's going to be hard to suck the solder out of the hole.  

Do y'all have any experience working with charred boards?  Should I just presume this thing is dead and find another NES motherboard to operate on?

[atom]

I would bet its dead if it melted any amount to warp the hole, the trace needs to hit that pin, so you can reroute the trace through a wire if you can find where its supposed to go.

[phreak97]

quick bursts should be ok, so long as the solder has melted all the way through before the first one. it's when the solder has only melted part way through, that the top half comes out and leaves a plug at the other end of the hole.

[Drewman21]

What i use with desoldering is a "T" joint for plastic tubing.  I put about 3 feet of plastic tubing on the t-joint to a PVC tubing cap with a hole drilled in it.  I hook that up to my Dyson vacume and use that to suck out the solder after a little heating up with the iron.  The tube can be closed off with  finger and the suction will pull it up.  Works great for alot of solder like a NES PPS or even small pins.  All you have to worry about is getting the hole against the board.
    I was looking at hooking the Dyson to a radio shack desolderer with a off/on valve for the airflow.  Still need to work out the kinks with it though.

Drewman21

[Adeptus]

woah Drewman... sounds like a Tim the Toolman solution...
(how do you spell "arrh arrh arrh"?)

[atom]

I do my desoldering with my space suit in a sealed vacuum chamber. I heat up the solder, and it just falls to the floor! *SHOCK*

[phreak97]

atom, even in a vacuum, the solder will still stick to the board., it just means the solder will fall at the same speed as everything else if you drop some.

[viletim]

Here's a method to remove DIP ICs from double sideded, through-hole plated boards.

Get a blow torch, set it on low (with a fluffy flame) and heat the underside of the board for a few seconds to let the solder melt. Then bash it down on the bench, all the solder falls out. Heat it up again and this time turn it upsidedown and bash the top against the bench. The IC falls out.

It sounds a bit rough but it works well (after a bit of practice) and lets you remove ICs that you normaly can't remove without destroying the board.

The main problem with it is that some older boards are too flammable and tend to burn before the solder melts properly.


btw, phreak97, you doing that 3yr electronics trade corse?

[phreak97]

im not exactly sure how long it goes for, but i dont think it's a trade course in any case. it's the course you do to start from beginner level and work your way up to a diploma in advanced electronic engineering. i just got up to surface mount components in my soldering class..

[viletim]

ah yeah...I think I know the one you mean. I was considering one of the diplomas but I decided to drop out of school and do the trade corses instead.

SMDs at tafe! that doesn't sound bad at all. When I did the soldering module (about three years ago...I think) we spent most lessons making animal sculptures out of 50 year old resistors (had to scrape the corrosion off each one :).

[phreak97]

lol.. viletim, are you here in australia? the course im doing now is called electrotechnology certificate 2

[viletim]

yup - Sydney

[phreak97]

awesome. adelaide here.. not so awesome

[Adeptus]

Nothing wrong with Adelaide!  :angry:

I don't know why some Adelaideans are so down on the place, I think it's a great place to live.

So how many Aussies are on here now? Me, phreak, viletim, Lawrence (he's a resident, if not a citizen... by the way, how are you liking it here?), any others?

[phreak97]

im down on the place because from my point of view, it is boring, useless and contains nothing of interest to me. sure it can be fun if you have the money, but i dont.. i'd be happy if there was ONE good arcade here.

[atom]

atom, even in a vacuum, the solder will still stick to the board., it just means the solder will fall at the same speed as everything else if you drop some.

Actually phreak, part of the reason the solder stays in their so snug is because gravity can not overcome the air pressure pushing both up and down on it at the same time. Do you know of the capillary effect? Of course the property of solder bonding to hot surfaces will help keep it in there as well.

[phreak97]

yeah, it was the bonding i was referring to

[Bostich]

Add one more badly damaged NES board to my collection.

I would have expected to do better the 2nd time, but this one is damaged worse than the first.  

Since it seems to be a lost cause for me to desolder a PPU without damaging the board, I think I am going to take atom's suggestion and try re-routing the traces through wires.  I found a schematic for the NES last night so I know where those pins should be connected.