Mill power feed has died; what do I check?

Whenever I solder electronics that are subject to vibration and environmental stress, I like to use rosin core silver bearing solder (low temp electronic solder, not to be confused with hard silver solder). The stuff flows like a wet dream, and is very strong without being brittle. It's like the 7014 electrode of the electrical soldering world, it will make anyone look like a pro.
 
Boswell said:
sounds like lack of flux. Is the solder you are using a flux core solder?
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I am using "Fine Electrical Rosin Core Solder" that states it is 60% tin and 40% lead. It's 0.050" diameter.

The soldering iron is an Ungar #1237 37-1/2-44W unit Made in the USA.

Here is the tip of my soldering iron:
DSC01138 (2).JPG

I'm guessing, based on the comments, that I need to clean the tip. Fine sandpaper or file, correct?
 
Yep, file. And you need to "tin" the hot tip so it has a shiny solder coating, and wipe the tip on a damp sponge from time to time and add fresh solder.
Some import solders are defective and impossible to use-I discovered that years ago. Kester with the "44" rosin core is my go to
 
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ARC-170 said:
I am using "Fine Electrical Rosin Core Solder" that states it is 60% tin and 40% lead. It's 0.050" diameter.

The soldering iron is an Ungar #1237 37-1/2-44W unit Made in the USA.

Here is the tip of my soldering iron:
View attachment 437380

I'm guessing, based on the comments, that I need to clean the tip. Fine sandpaper or file, correct?
Click to expand...
Yeah, the tip needs to be cleaned up. Won't get efficient thermal transfer with all that crud on there. Filing can remove any plating that was on the tip, sometimes all that is needed is a light scraping when the tip is hot, followed by tinning. But if a tip is too far gone, and you don't have a replacement you need to file to clean metal and tin it immediately. You want the whole chisel area to be solder coated, the round part behind doesn't need any treatment as it isn't used for soldering. The chisel area is what contacts the board. The very tip needs to be clean as well.
 
I think you can safely file that tip- looks like an Ungar copper tip. It's the iron tips that shouldn't be filed
 
You may not need to file the tip at all. Just let it get hot and wipe it on a wet rag. Unless it is badly corroded it should get shiny again. If this doesn't work, try scraping the tip with an exact knife. I don't think filing the tip is ever a good idea. This will then transfer heat into the solder joint better. Let the tip get good and hot, and "wet" it with fresh solder as someone already suggested. Hold the heat to the solder joint long enough so the solder will "flow". Otherwise, you'll get a cold "lumpy" joint that can fail again. A 40W tip may not be hot enough to heat up that joint and power resistor lead adequately. The lead on that power resistor will act somewhat like a heat sink.

Check all the other solder joints as well. Some others may be on the verge of failing as well.

I'm a retired Electrical Engineer. Much of the "gadgetry" that was brought to me, over the course of my career for repair, was due to bad solder joints. Sometimes "hitting" every solder joint on a board would fix hard-to-diagnose problems. Particularly if a board was stressed like the OP says his board was "press fitted".
 
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