Help on desoldering transistor

[gobbler]

Hi guys,

Does anyone has experience in desoldering this kind of transistor in the centre?

[kikkoman]

Re: Help on desoldering transistor

though this can be done with a sufficiently powerful iron (80W+) i'd rather use a hot air gun.
aluminum foil and kapton tape work well for shielding the other components. preheating the entire board would be a good idea to prevent excessive thermal stress.

[gobbler]

Re: Help on desoldering transistor

Hi kikkoman, do you mean using powerful iron (80W+) on the top part of the transistor? Thanks.

[kikkoman]

Re: Help on desoldering transistor

on the metal slug, yes. (a soldering iron, of course). using lots of solder and flux helps with getting enough heat to the slug.
you should unsolder (or clip off) the two smaller pins first

[Toasty]

Re: Help on desoldering transistor

Do you mean the pictured transistor specifically, or one like it?

If that one, what makes you believe it's bad?

If that board, I'd replace those caps first.

If one similar, then all suggestions given are good. But, use at least a hair dryer on high, 2-3 inches from the back of the board to pre-heat the area. Then with the dryer still on, do the removal. Those tabs are soldered to a large area and will suck all the heat from the iron. It takes some juggling, but it is possible. Be cautious working around any SMD components as they can easily be dislodged.

Toast

[Krankshaft]

Re: Help on desoldering transistor

If you really want to remove it easily without a hot air gun just get some chip quik. Watch the video on the site to see how it works.

Ripping traces isn't fun.

It's your best chance for success I take from your post you don't have much SMT soldering experience.

I'm with the others though on this one turn to the caps first.

[japlytic]

Re: Help on desoldering transistor

I don't seem to bother with such surface mount devices.

[Toasty]

Re: Help on desoldering transistor

@Krankshaft-

I didn't think Chip Quik would work on that large of an area. Thought it was just for small area such as multi IC leads. Hmmm. Something to experiment on. TY

Toast

[gobbler]

Re: Help on desoldering transistor

Hi, the picture is for illustration purpose only. I have a faulty graphic card, there are 2 transistors side-by-side. I tested onboard, one of it seems to be shorted. After reading, there is so much investment to revive this really old graphic card, I feel not worth it. Maybe I will give it a miss. Thanks.

[lucky13]

Re: Help on desoldering transistor

gobbler,

If you think it is not worth your while to revive your card, you may still want to use it for practice anyways instead of throwing it into trash (especially if you have the soldering iron to try). Then you can post back here with your experience to share with us.

[Toasty]

Re: Help on desoldering transistor

Hi, the picture is for illustration purpose only. I have a faulty graphic card, there are 2 transistors side-by-side. I tested on board, one of it seems to be shorted. After reading, there is so much investment to revive this really old graphic card, I feel not worth it. Maybe I will give it a miss. Thanks.

How about some info on what you are working on? A picture of the card and problem area, the model & type. Someone may have this same card and help.

On checking transistors in circuit- you really can't unless you know the surrounding components are not giving false readings.

I asked what makes you think this is bad. Card symptoms? No output? Incorrect display?

Toast

[gobbler]

Re: Help on desoldering transistor

Hi, the soldering iron I owned now is only 30W. I will need to buy a new 80W soldering iron to practice desoldering the SMT. I also have a faulty P3 motherboard to practice on SMT once I get hold of the 80W soldering iron.

The graphic card is Inno3D FX5700, it does not have output. Had checked all the caps ESR, all are good.

Just got hold of a faulty MSI845 Ultra motherboard, does not post. CPU fan spins. No bloated caps. All using rubycon. Any help will be appreciated. Thanks.

[Toasty]

Re: Help on desoldering transistor

Desolder the 2 legs of the suspected transistor for testing. Be VERY careful as it is easy to tear the board pads/traces where they attach. If it still shows shorted, then you likely have the correct component.

Did the fan on this card ever stop working perhaps causing the chip to overheat?

What did you use to check caps ESR?

re: MSI845 mobo. Start a new thread in the motherboard section. Adding another item here will assure it gets overlooked.

Toast

[gobbler]

Re: Help on desoldering transistor

Hi,

I have tried desolder the 2 legs, it still shows shorted on my DMM. It is a passive heat sink, not fan type for this graphic card.

I used EVB ESR meter to test the caps.

Ok, will start a separate thread for the MSI 845 Ultra mobo. Thanks.

[lucky13]

Re: Help on desoldering transistor

gobbler

This your card? I found using Google images..

[momaka]

Re: Help on desoldering transistor

If you have already desoldered the legs off, just heat the metal tab/heatsink/metal plate of the transistor with your iron and pry it up with a small screwdriver. This should remove if off the PCB. At least that's how I did it with my limited experience for a few similar transistors without damaging the PCB.
Done with 60watt RadioShack iron by the way. Your 30 watt iron might work if it has a good tip (if not, add a little solder to the tip for a better heat transfer).

[gobbler]

Re: Help on desoldering transistor

lucky13, yes that the one.

momaka, let me try with my 30W solder iron.

[gobbler]

Re: Help on desoldering transistor

Hi momaka, I managed to remove the SMT with my 30W solder iron. I used alot of solder and managed to remove it fairly easily. Now the problem is, my local stores does not sell this transistor, SDB60N03L. Maybe will KIV for awhile. Thanks.

[gobbler]

Re: Help on desoldering transistor

Hi Guys, I have got good news. I happened to have a faulty P3 mobo, it has 2 transistors CET CEB6030L. Specifications wise quite close to the SDB60N03L transistor. I desoldered it this time quite easily since I had experienced with the previous one. I soldered it on the Inno3D FX5700, it looks ugly though. Viola, the FX5700 is revived! It can display now but the passive heat sink is damn hot. Maybe when I have time, I will let it run for a couple of hours. Thanks for all the help given.

[momaka]

Re: Help on desoldering transistor

Nice job! Glad everything worked out fine .
Just check the transistor to make sure it isn't running too hot. As for the card running hot, bolt on a fan on the heatsink and run it at 5v. If it's still hot, run the fan on 12v.