Need a soldering expert (electronics) - Help me Mr. Wizard

S

SAK

Joined
Sep 28, 2001
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508
I would like to thank General Motors. When the lights for their radio buttons go out (in a GMC truck) they made it virtually impossible to correct the problem. First you need infinite patience and infinitesimally small fingers to open up the radio and get to the bulbs. Then you find out they are soldered in place. Out of the 10 original bulbs, only one is still working.

I will need to remove all 10 of these two-pin bulbs and install new ones. I would really hate to screw up my radio, so any advice would be appreciated. I have soldered some over the years but it has mostly been larger gauge wire-to-wire or wires-to-speakers. I have never soldered small components into a circuit board – and these bulbs are pretty tiny.

I do have a solder sucker, so I should be able to get the old components out. Can someone give me do’s and don’ts for the rest of the job? And what type of solder should I use?

Thanks,

--SAK
 
I'm guessing you mean LEDs here.... don't know of too many 2 lead bulbs.

A fine tip on a soldering iron and a little patience with solder wick will probably get you further than the solder sucker. I usually remove surface mount parts with 2 irons at work (650deg) (and I work with parts 1mmx0.5mm)... through hole gets the 40watt iron or 700deg (the choice of solder sucker or wick is decided by working space).

The flat surface is the negative (aka ground) lead. Keep in mind your dwell time when replacing the LEDs, they will burn if you go too long (though when the lead starts glowing you have bigger problems than the LEDs)

As far as solder, standard solder should work fine. Even our stuff is 90% lead/tin solder. Only one product on my line is lead-free... another line uses lead-free on everything. I'll tell you now, lead-free is a PITA to work with, not very forgiving.
 
Sounds like you are describing the tiny bulbs we used to have to replace in and around aircraft instrument panels and controls. Those little blue bulbs were called "wheat bulbs" because of their resemblance to a grain of wheat I suspect. They were a pain in the ass to work on, too! If you have an avionics shop in town (probably at your airport) you might want to go talk to somone there who can either advise you or actually replace your truck's bulbs for you. Just a suggestion. Something we used to make it a little easier was one or more pair of small hemostats to hold the leads with. If you use a non-automotive (read: aircraft) bulb, be sure the voltage requirements are the same. The ones we used went into a 24 volt DC system, but I think they used a resistor to step the voltage down for the little bulbs. It's been awhile, so I'm not sure now. If you decide to use LEDs keep in mind that they are polarity sensitive, and be sure of your voltages here, too. LEDs should be far superior if you can find some that are compatible.
 
VampyreWolf said:
I'm guessing you mean LEDs here.... don't know of too many 2 lead bulbs.

A fine tip on a soldering iron and a little patience with solder wick will probably get you further than the solder sucker. I usually remove surface mount parts with 2 irons at work (650deg) (and I work with parts 1mmx0.5mm)... through hole gets the 40watt iron or 700deg (the choice of solder sucker or wick is decided by working space).

The flat surface is the negative (aka ground) lead. Keep in mind your dwell time when replacing the LEDs, they will burn if you go too long (though when the lead starts glowing you have bigger problems than the LEDs)

As far as solder, standard solder should work fine. Even our stuff is 90% lead/tin solder. Only one product on my line is lead-free... another line uses lead-free on everything. I'll tell you now, lead-free is a PITA to work with, not very forgiving.
Click to expand...


Great advice from both.

If they are LED's you have a bigger problem. You don't say what year your truck is but it would have to be pretty new to have LED's and that would make me wonder how they "blew". If it is older then it is bulbs. I also recommend the solder wick/braid. It is easy to use and does a great job. Like Dr. Mudd says if they are LED's or your planning on replacing the bulb with LED's you have to worry about polarity and also current limiting if you are trying to use them as a replacement. I also agree that I never, never use the lead free solder. I used it once, I expect I never will try it again. Everyone that does use it and my one experience with it, well, it sucks.

Just be careful and use and appropriate iron for the job. Too big an iron and you will damage the component and possibly also the board.

Good luck,
KR
 
These are definitely bulbs and not LEDs. The leads go through 2 thru-holes in the circuit board.

They look something like this: http://www.radioshack.com/product/index.jsp?productId=2103780&cp
I had to order the exact bulbs from a specialty place that supplies parts to electronic repair shops.

I am guessing they are maybe 2-3 times the size of a grain of wheat (it has been a while since I really examined a grain of wheat).

A solder wick/braid is something you buy?

Thanks,

--SAK
 
It's probably not lead-free solder. The automotive industry is exempt from lead-free soldering requirements for the time being. Do not attempt lead-free soldering unless you've had proper training and have a very good iron. The process window for lead-free solder is very narrow; you have to do it just right or your joint will not be reliable.

A common mistake in soldering miniature electronics using a low-wattage iron. Miniature electronics needs a small iron tip, but not a small iron heater. The goal is to get the solder melted as quickly as possible before the heat migrates into the component and melts it.

I also agree that these bulbs are probably not LEDs. They're probably small light bulbs, 12VDC.

One good idea is to find a scrap circuit board with similar parts and practice a bit. Ask at repair shop or go to a thrift shop (eg Goodwill) or even a garage sale and look for a look for a little pocket radio or clock radio or something you can buy for a few bucks and then practice on before you attack your car radio.

Another little tip: the bulbs a dead. There's no reason to remove them intact. So, use a little wire cutters or pliers to carefully break the bulb and now you can remove the two wires one at a time which is much easier.
 
I just replaced the bulbs in the radio on my Chevy Silverado. Yes the bulbs are small incandescents and not LED's; I was surprised at this too. I asked for help on a truck forum called fullsizechevy.com. They deal with gm fullsize trucks and SUVs, and have lots of people who have done this and other work on their vehicles. They told me I could get bulbs at radio shack and even recommended the bulbs in your link. I picked up 10, installed them and they have been working just fine for three weeks now.

A couple recommendations;

Replace all of the bulbs, even the one that is working because you don't want to have to pull the radio again if it blows in 2 weeks. When I removed the old bulbs, I ended up breaking most of them, then you just have to dig out the glass from the little plastic cups they sit in. Since the radio shack bulbs were a little smaller than the stock ones, it was a little tricky to get them to stand up straight in the sockets. I held them in with one hand and dropped some solder from the iron on each of the leads with the other.

One good thing is that you can try multiple times to solder the bulbs without hurting much. The circuit boards are pretty resistant to heat and the bulbs are designed to get hot, just watch your fingers. Another thing is that it doesn't matter which lead goes in which hole like it does with LED's. Before you close up the radio though, check the points where you soldered each light to make sure that there are no solder bridges between the leads or any other connections on the board.

Good luck.
 
SAK said:
A solder wick/braid is something you buy?
Click to expand...

Desoldering Braid from Radio Shack

Place the braid between the soldering iron and the solder pad you want to take the solder off of. You heat the braid until it is hot enough so the capilary action pulls the solder off the pad and into the braid where it is trapped. Science is so cool. :cool: :D :thumbup: Once you get the hang of it, it works great.
 
First off - thanks for all the tips so far. I am beginning to feel like I can do this.

This question will be dumb - but here it is: I will have this very tiny gauge wire that has to get electrically connected to the trace on the board. Where should I be touching the tip to heat things up? - mostly on the trace, on the trace and the wire equally, or...?

Thanks,

--SAK
 
SAK said:
Where should I be touching the tip to heat things up? - mostly on the trace, on the trace and the wire equally, or...?
Click to expand...

Equally right between them.

Wet the tip of the iron with solder. Wipe the iron on a damp sponge. The rewet the iron with just a touch of solder.

You may need to add some solder to the joint as it melts to get it to flow nicely. I know that it sounds counterproductive to add solder when you're trying to remove solder. What you're really adding is flux. Most boards these days are fluxed with no-clean fluxes that are only active momentarily when the joint is first soldered. After that, the heat destroys the flux. So, there is no flux in the joint and you'll probably have to add some. The wire solder you should be using is actually a hollow tube and is filled with flux in the middle. You can buy liquid flux in a little bottle and paint some on before you start soldering, but that's an extra expense and really not necessary since you have flux already in your wire solder. Just add a bit of the wire solder to the joint.
 
Gollnick said:
Equally right between them.

Wet the tip of the iron with solder. Wipe the iron on a damp sponge. The rewet the iron with just a touch of solder.

You may need to add some solder to the joint as it melts to get it to flow nicely. I know that it sounds counterproductive to add solder when you're trying to remove solder. What you're really adding is flux. Most boards these days are fluxed with no-clean fluxes that are only active momentarily when the joint is first soldered. After that, the heat destroys the flux. So, there is no flux in the joint and you'll probably have to add some. The wire solder you should be using is actually a hollow tube and is filled with flux in the middle. You can buy liquid flux in a little bottle and paint some on before you start soldering, but that's an extra expense and really not necessary since you have flux already in your wire solder. Just add a bit of the wire solder to the joint.
Click to expand...

Yep, yep and more yep. Listen to Gollnick.

I use the solder with the flux in it. It flows great. Never needed to use extra. By the way you want light electronic solder. About as thick as a pencil lead. Don't try to use the solder that is used to solder pipes. You won't be satisfied witht the results. :D

KR
 
VampyreWolf, Dr. Mudd, kr1, bexteck, Gollnick, and GarageBoy; thank you for all your good hints and tips. That is exactly the type of information I was looking for.

I now have my 1 millimeter diameter 60/40 (tin/lead) rosin core solder, my 2mm wide solder braid and an old circuit board to practice on. My new bulbs should arrive later this week.

I will let you know how it turns out.

Thank you,

--SAK
 
SAK,
I am an aerospace technician at Goddard Space Flight Center and work on a lot of very small electronic components on printed circuit boards. I use a lot of specialized tools, procuction supplies, etc. for soldering/desoldering. Use a microscope 99% of the time to soleder/desolder. I would be more than happy to do the work for you.
 
Enlightenment! Wooohoo! Success!

Thanks to your help I was able to replace all 10 bulbs successfully and my radio is no longer dark. That solder braid works incredibly well – much better than the solder sucker. Thanks for telling me about that.

md lou, thank you for your very kind offer. I almost took you up on your offer just so I could tell everyone that part of my truck had been worked on by an aerospace technician from the Goddard Space Flight Center.

(Man, there are as many, or more, forums for full-size GM trucks as there are for knives.)

--SAK
 
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