Friday, September 7, 2018

Review and use of: Katsu ZD-8915 Desoldering Station

Desoldering through-hole components with two or three legs, is pretty straightforward. Apply heat and some fresh solder to the underside and pull them out from the top. But when it comes to chips and modules with more pins, this approach doesn't work. 
Some people manage to master the use of the small pen-shaped 'solder-suckers'. The idea is that you melt the solder with an iron, and as soon as the solder is molten, place the solder-sucker over the joint and release the spring to suck up the solder. I've tried and failed to learn that skill.
Enter stage left, the desoldering station.

These use a hollow tip soldering iron and a vacuum pump, so that solder removal is a LOT easier than trying to use a pen-style solder-sucker.
I bought the model shown (Katsu ZD-8915 Desoldering Station) from Amazon, but they are also available on eBay and I'm sure elsewhere too. 

What you get

The package included:
  • the control unit, that shows both the actual and set temperatures (up to 480C)
  • de-soldering gun
  • two spare tips of different hole sizes, giving you three tips in total (1.0, 1.2 and 1.5mm)
  • a good solid stand for the desoldering gun
  • spare wadding pads 
  • three sizes of cleaning tools to poke out the solder from the hollow nozzle
  • a factually correct but not very informative instruction book
Everything fitted together very well and actually felt like it was pretty good quality. The solder chamber containing the spring-loaded piston has to be occasionally emptied of solder and at first time is a bit confusing, as the wadding and metal disk just sit against the spring and fall out when you open up the chamber. Putting it back in, it took me a while to realise that the wadding pad goes in first, followed by the metal disk. After using the gun for a while I realised why there were spares of the wadding, as it gets spattered with solder.


I gave up on the instructions, which don't really explain how to use the gun and just watched a few YouTube videos.

Here's what I found to work for me, desoldering some DIL 7-segment LED modules for practice.
  1. Push the back of the piston down to prime the spring
  2. Apply heat to the solder joint until the solder melts (applying a bit of fresh solder and adjusting the temperature as required)
  3. Pull the trigger to turn on the suction pump
  4. Adjust the angle of the nozzle to get as good a fit over the solder joint as possible. I found that if you listened to the vacuum pump you could hear it work harder when you get a better seal.
  5. Release the piston to make the final suck and you should see a splodge of solder fly up the see-through piston and embed itself in the cotton. Thats the fun bit!
  6. Inspect the joint and repeat if necessary.
  7. Get a flat-bladed screwdriver under the thing you are desoldering and gently lever it out - desoldering some more if it won't move.

Feeling very pleased with my new purchase, I turned it off and went and had some lunch. When I came to start again, it didn't seem to be sucking.

If I had read the instructions properly, I would have noticed the section warning me to ALWAYS ROD OUT THE NOZZLE BEFORE YOU TURN OFF THE HEAT!

I had bunged up the nozzle, just where it meets the cylinder. It then took about an hour of poking, changing the temperature, running in more solder and even pouring in liquid flux. Eventually I unblocked it by taking the front off the gun and poking the solder out by rodding it from the other side.

Obviously this was entirely my fault and I'd like to say I have learned my lesson, but its quite possible that I'll forget again. 


Admittedly, this is the only desoldering tool that I've ever owned, so I don't have anything except the solder-sucking pens to compare it with, but I have to say I was very impressed.
This has already more than paid for itself because I had some expensive modules that I really needed to reclaim. Overall, the quality is pretty good and I didn't expect it to be as easy to use as it was.

If like me you have some high value components, or a PCB that can't easily be replaced then I can recommend this tool. It really does work. 

Just remember to clean it out before you turn it off.

No comments: