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The MAC MANIAC!

Broken solder joints

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 I got a macintosh plus off of eBay for about 400$. The owner said it was working when he sent it but when it arrived it seems to have broken solder joints. He may have lied or it got damaged in shipping for some reason. The picture appears for just a split second when thumping it on the side. I have seen others with this problem and it seems to always be the analog board's Solder joints. I wanted to know what steps do I take and what solder iron should I use? preferably one that would be cheap and affordable.

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29 minutes ago, Unknown_K said:

and make sure you use the old lead solder with rosin core.

This is absolutely crucial! The lead free stuff, while less toxic, sucks.

 

I would also recommend a temp-controlled soldering iron. I’ve got a 75-watt one I got for around $70 or so, IIRC. Well worth it. It’s not the best one in the world, but it’s been working great for me for almost 5-years now. 

 

A lot of people think they can’t solder because they’ve probably been using a cheap iron with lead-free solder, which you can’t do sh!t with! Once you get a decent iron and some good leaded solder, it’s super easy. Flux also helps a lot.

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Yes, a temp controlled soldering iron is the safest option for sure. I'm not a fan of fixed temp irons myself, and while you'll pay more, I think it's worth the investment.

 

AIt would be best to remove all the old solder and redo the joint. Also, a container of liquid or gel flux will aid in the removal of the old solder, and as said, rosin core lead solder will make things a lot easier when repairing.

 

I would also get some solder wick as well. I like it more than a solder sucker, and it's cheaper than a vacuum, but that's personal preference.

 

I'm guessing this is all on the analog board? Some of the traces can be pretty fat, so don't worry if it takes a bit longer to melt or apply the solder to those joints. I am super paranoid while soldering, and knowing this takes a lot of the edge off the job.

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Another trick: if the solder is heavily

oxidized or otherwise covered with some

junk, paint it with some flux and then heat. It will usually cook off the junk and allow you to melt the solder.

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The reason a bad solder joint is heating up is because a bad connection works like a heating element (resistance to a line where there should not be any). Not really a good idea to leave it as is because heating and cooling cycles will just make the connection worse, create a bigger load for the old power supply, and possible cause a fire depending on the voltage to that line.

 

My 110 disc CD changer  had a bad connection on one of the RCA outs to the receiver (low voltage signal). The right side speaker either worked OK, played at a lower volume, or just cut out. This is a 90's Technics unit that used lead solder so I just melted the solder that was there and added a little more. If the solder looked oxidized I would have used my desoldering gun to suck it all out and then used new solder. Nonleaded solder is much more of a pain to work with since it needs higher temp to melt and flow plus it cracks much easier and you generally need flux to make it flow,

 

For equipment I use a temperature controlled soldering iron and hot air rework station if I work on motherboards and cards, and a cheaper manually dialed soldering pencil for stuff that doesn't have circuits in them where precision temp isn't that important. The major difference between the two is the 2 plug electrical cheap irons are not grounded while the 3 plug ones are. Without the ground you can build up a voltage and ESD some part with a discharge.

 

 

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Ok, update :

I'm going to the hardware store tomorrow and getting a Temp Controlled solder iron with a grounding plug if possible, some rosin core solder that contains lead, and solder wick. I also have the tools to open it already and am prepared to discharge it. 

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30 minutes ago, The MAC MANIAC! said:

What should I set the temperature on the iron?  I also decided to purchase a massive set of caps to replace the old ones with. This will be my first repair of this scale!

In JDW's video, he says 350 C / 662 F, but I typically start at around 500 F on my weller station and go up if need be for projects like guitar stompboxes, Though I just looked at mine from the last solder job I did (SE/30 analog board) and it's set at 550 F. If it's a component on a large ground pad, hotter might be better in this case.

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Lead solder melts at something like 183 Deg C so you want to set the temp to something like 100C higher then that to get a good melt. If you are soldering a part that is large and the board is acting like a heat sink you bump it up some more. So try 300 Deg C and go from there. You have to factor in the heat recovery of the soldering iron (how much the temp drops when in contact with the part you are soldering and how fast it gets back to temperature which is a product of the heating coil wattage and the weight of the soldering iron). Some people crank the temp up for fast soldering but that reduces the life of the heater and can burn the board if you the iron in contact with the part for too long. Remember while you are heating up the solder you are heating up the part you are soldering also and liquid filled capacitors don't like excess heat.

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Great news everyone I got it working. I had to use a temperature set solder iron but with the right type of solder, it worked fine! Now it boots up in 3 seconds instead of minutes. 

I also plan to do a Caps replacement repair in early 2020!

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