How to unsolder transistor

[Rockguy]

Hi everyone, I am going to unsolder a transistor from a tv board. It's a 5N2307. Its the exact one in this thread. Same tv. https://www.badcaps.net/forum/showth...ght=TH-42PZ77U

I have soldering irons. Weller WES51 and a 100 watt solder gun. I don't have a hot air station but, I would get one if it's the way to get this done. I'm a hobbyist so it would probably come in handy later anyway.

If you can give me a complete idiots description, I'd appreciate it.

[stj]

Re: How to unsolder transistor

use the wes to heat each leg, and lift the leg a bit with a needle when the solder melts.
then clean the solder off with braid or a pump.

once the legs are free the wes can be used on the tab to melt the main joint and you lift the part off with longnose pliers.

keep the 100w destroyer in it's box.

[selldoor]

Re: How to unsolder transistor

Weather in illinois looks as good as here!! - Sometimes helps to work in a warm rom and to gently preheat the board with a hairdryer - reduces the heat from the iron dissipating into the board/heatsinks.

[mariushm]

Re: How to unsolder transistor

Put the 100w iron away, it's too powerful for this.

Put the other iron on the tab of that mosfet and warm it up a bit, then add solder on top of the tab. Add some solder on each leg of the mosfet as well.

Now keep applying the iron top on top of each metal part for a few seconds or until you see the solder liquid and move to next (warm up solder on tab, move to each pin, repeat, the idea is to warm up everything).
When everything is warm enough, just from the gentle sideways pressure of your iron tip, the mosfet should slide away from the location and then you can pick it up .

[Rockguy]

Re: How to unsolder transistor

use the wes to heat each leg, and lift the leg a bit with a needle when the solder melts.
then clean the solder off with braid or a pump.

once the legs are free the wes can be used on the tab to melt the main joint and you lift the part off with longnose pliers.

keep the 100w destroyer in it's box.

Thank you. That's what I did. Looks like I need some repair now though

Any suggestions?

[Rockguy]

Re: How to unsolder transistor

Weather in illinois looks as good as here!! - Sometimes helps to work in a warm rom and to gently preheat the board with a hairdryer - reduces the heat from the iron dissipating into the board/heatsinks.

Good idea. Wish I'd waited for replies before doing this. I've got it in the house. 72 degrees in here.

[budm]

Re: How to unsolder transistor

I cut the legs off (no need to keep the legs since it is bad part any way) first then add solder and flux to the tab to remove the main body.

[Rockguy]

Re: How to unsolder transistor

Put the 100w iron away, it's too powerful for this.

Put the other iron on the tab of that mosfet and warm it up a bit, then add solder on top of the tab. Add some solder on each leg of the mosfet as well.

Now keep applying the iron top on top of each metal part for a few seconds or until you see the solder liquid and move to next (warm up solder on tab, move to each pin, repeat, the idea is to warm up everything).
When everything is warm enough, just from the gentle sideways pressure of your iron tip, the mosfet should slide away from the location and then you can pick it up .

Thank you mariushm. On the non tab side, there is no visible solder other than the legs which as you know, stick away from the body of the component itself. All I see is green board. Anyhow, I wasn't sure I'd get any replies so I gave it a go before getting this. You see the results

[Rockguy]

Re: How to unsolder transistor

Love your sig links budm. Added you to my contacts so I can read them at a later date.

[selldoor]

Re: How to unsolder transistor

[QUOTE=Rockguy;525366]You see the results[/QUOTE

Oh no we dont!

[Rockguy]

Re: How to unsolder transistor

[QUOTE=selldoor;525369]

You see the results[/QUOTE

Oh no we dont!

It's above and now here too

[mariushm]

Re: How to unsolder transistor

Good.
If you don't have liquid flux, add a tiny bit of solder to that square and move it around to spread it evenly and mix with the solder that's still in that area. Then, remove the solder using solder sucker or solder wick.
When you install the new mosfet, ideally you'd put a drop of liquid flux on the mosfet tab and the copper pad and apply a bit of solder on the copper on the pcb. Then, put the mosfet and heat up the tab of the mosfet which in turn will melt the solder under the chip and the chip will be soldered onto the pcb.

The legs are much easier, you just heat up the leg and introduce solder where leg touches the small copper pad. Ideally you should also use liquid flux there, but if you have a good solder with flux inside it, then you're good to go.

[Rockguy]

Re: How to unsolder transistor

Good.
If you don't have liquid flux, add a tiny bit of solder to that square and move it around to spread it evenly and mix with the solder that's still in that area. Then, remove the solder using solder sucker or solder wick.
When you install the new mosfet, ideally you'd put a drop of liquid flux on the mosfet tab and the copper pad and apply a bit of solder on the copper on the pcb. Then, put the mosfet and heat up the tab of the mosfet which in turn will melt the solder under the chip and the chip will be soldered onto the pcb.

The legs are much easier, you just heat up the leg and introduce solder where leg touches the small copper pad. Ideally you should also use liquid flux there, but if you have a good solder with flux inside it, then you're good to go.

Remove the solder? Is that all that is missing from this board is old solder or, did I pull up part of the board too? I'm too much of a novice right now to know. My previous soldering has been either through hole or, no board, just wires themselves. I have paste flux. I could order liquid. My solder is Kester rosin core 60/40

[stj]

Re: How to unsolder transistor

it looks to me like you ripped the copper pad apart!

[canadaboy25]

Re: How to unsolder transistor

Yup that's ripped apart. A little part of one of my pads came up (miniscule piece, not that big) and that's what it looked like underneath.

[Rockguy]

Re: How to unsolder transistor

So I'm thinking that if I flow solder in there, it won't stick.

[mmartell]

Re: How to unsolder transistor

I think you'll be fine. Trace those connections then verify with your meter they are still good then flow some solder on the large pad and see what you've got.

[Rockguy]

Re: How to unsolder transistor

I think you'll be fine. Trace those connections then verify with your meter they are still good then flow some solder on the large pad and see what you've got.

Isn't the area underneath the transistor itself just a copper pad used for cooling and hold down?

That's what I was gathering from Tom66

[stj]

Re: How to unsolder transistor

no, it's a 3rd connection.

[SteveNielsen]

Re: How to unsolder transistor

It is all three, it is one of the transistor connections, a heat sink, and how it is mounted to the board. The only thing I'd be concerned about is sufficient heat transfer since more than half the copper is gone.