RoadTest: Cool Tools: Desoldering Station - 110V
Author: gordonmx
Creation date:
Evaluation Type: Workshop Tools
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: Aoyue Int474A+, CSI474A
What were the biggest problems encountered?: Very poor documentation
Detailed Review:
First off, I would like to thank Element 14 for the opportunity to evaluate the Tenma 21-19700 desoldering station, although I thought a CoolTool road test would be so much effort.
Summary Conclusion –
As mentioned in the body of my review, the Tenma 21-19700 desoldering station is a low cost compact desoldering station for the low volume or hobbyist shop. The station offers clean solder removal for both leaded and lead-free solder connections on PCB and leaded components. Although the station performs well, the documentation is very poor. Best suited for through-hole and leaded components.
Pros –
Cons –
Aside from improving the documentation, the following items should be included in the kit:
Related Document Links-
PCB Rework and Repair Guide by Intertronics
http://www.intertronics.co.uk/wp-content/uploads/2017/05/PCB-Rework-and-Repair-Guide.pdf
Solder Wiki
https://en.wikipedia.org/wiki/Solder
Basic Soldering Guide
https://technick.net/guides/electronics/how_to_solder/?aiocp_dp=how_to_solder
Tenma 21-19700 User Manual
http://www.farnell.com/datasheets/2365580.pdf
Aoyue Int474A+ User Manual
https://www.aoyue.eu/media/manuals/90/90474/EN/90474_Aoyue_Desoldering_Station_en.pdf.pdf
Preface –
Have you ever had the feel that someone was looking over your shoulder? Maybe even thinking your same thoughts? Well, that is how I felt while reading Russ (rusgray) remarks concerning the Tenma 21-19700 desoldering station. As I was writing my review, I pulled up the link to the review site and saw Russ’ review. I noticed many of the same issues, so I’m glad I wasn’t the only one with concerns. After all E14 owns and operates Tenma and I would like to do more reviews in the future.
This was my first equipment review in a while so I was excited to road test the station, not just because I could use a new rework station, but because is gave me a chance to check out a new equipment vendor, Tenma. The station is currently available to order through E14.
Part I – The Arrival: 8^) with a little 8^(
Very much like rusgray, the box arrived damaged, never a good sign. The shipping carton was made of light weight cardboard. There was a 3” hole in one of the corners. The main control unit was in a plastic bag and surrounded by a protected cardboard cover, but still a small dent in the chassis. The other components were loosely packaged and scattered throughout the box.
Part II – The Unpacking: 8^) with a little 8^(
Welcome to the first part of many of my evaluation of the Tenma 21-19700 desoldering station (“the station”). I have read many different views on the value and/or Importance of the unpacking segment, but I feel it is important because it is often our first glimpse into what to expect in the product and support.
Aside from the shape of the delivered package (see above), everything listed in the manual, although not all the items included had instructions (i.e. cleaning drill & silicone grease), was included.
The box contained the main control station and desoldering gun along with the following accessories:
From the point of actually using the desoldering station, there were some Items that could have been included that would be very useful:
Since this a low end, small project/hobby originated station, used by less experienced operation it would be useful to included links to a PCB rework guide like those mentioned in my related documentation section.
Part III – The Setup, Operation and Maintenance
Some assembly was required, and despite the lack of details in the manual, was pretty easy to figure out. The front panel is labeled fairly well. The temperature control is only labeled from 1 to 8, with no indication as to how that translated to the actual nozzle temperature. Thanks to the data supplied by ralphjy’s roadtest, the scaling appears to be somewhat linear with a range of approximately 230C (1) to 460C (8). The manual lists the temperature as 150C to 380C. NOTE: Soft solder used in electrical circuit typically has a melting point of ~190C (Sn/Lead) or ~210C (RoHs lead-free). For a good clean solder contact, typical soldering iron operates in the 330C to 350C range. The only label that is confusing is the “cal” button under the temperature control knob since the manual is silent about it. This may be a holdover from an earlier model (see spoiler section).
There were a couple of caution labels attached to the station reminding the operator to remove before use the screw used to secure the internal vacuum pump for shipping.
The cleaning procedure is pretty much “learn as you go”, since the manual is silent in this area. From other documents I’ve found on the web (see related documents section), it appears the silicone grease may be used to clean difficult components of the station, but remember some components may be very hot, making the grease very hard (and dangerous) to work with.
This is where my most difficult (and time consuming) learning portion of my review comes in. In the past I’ll tended to shy away from videos in the past because I’m told I neither have a face for TV or a voice for radio, but the manual for the station is written so poorly, that actually showing you how to perform some operations is better that 1000 words. I apologize in advanced for my poor video and editing skills, but like I said, this is a learning experience for me. It the video I do mention some things I have discovered that I later will I will expand upon in my later “spoiler” section.
One thing I forgot to mention was an additional filter, and not mentioned in the manual, is located in the vacuum connector on the station.
Part IV – A Peek Inside
The layout of the inside of the station is very clean and straight forward. The station includes an integrated vacuum pump. The original design used an AC pump that ran directly off the power transformer. The current design uses a DC pump, still runs off the power transformer, but through a small rectifier board attached to the station back panel. The power transformer also runs the heating element, so as you turn up the temperature, the voltage to the pump decreases. I did not measure the drop in vacuum versus temperature. As mentioned in the video, the pump noise also changed as the temperature was changed. Also as mention, the pump outlet (not intake) is inside the enclosure and may benefit from a vent in the case.
The control board is attached to the front panel by the temperature control potentiometer shaft and the heating iron control connector. The front panel “cal” button backs up to a component on the control board, but no further information about its function or operation is given. It may be a left over from an early design since newer versions (more spoilers) do not have it.
Part V – The Test
The documentation claims to be ESD-safe with less than 2mV tip-to-ground potential and less than 2 ohms tip-to-ground resistance. My measurements were well below these values, but I should note that it is just as easy to destroy a component by discharging through a low resistance.
I did not measure the noise level, but as mentioned in my video, the station is possibly too noisy for some environments, but that something could be done to reduce the effect.
I ran a comparison between a low cost solder sucker ™ (item “A”), solder wick ™ (item “B”) and the 21-19700 station (item “C”) for different component removal. I used RoHs solder in my test, since the resin-free solder seems to be more difficult to de-solder. During desoldering, I used a flux pen (as shown) to prep the board before desoldering. After desoldering, I use isopropyl alcohol to clean the board.
The first test used components on a small pad test board. Each solder joint was made using 1/8” strip of solder. I then applied flux and de-soldered the components and compared the holes.
The results look very comparative, the pads using the “solder sucker” (A) looked a little worst on the component side.
The second test used components on a large ground plane test board repeating the procedure from test 1
Again the results looked very comparable.
A third test was performed on a loaded PCB and outlined in the following video. Grab your NoDoz. 8^)
For the most part, the Tenma 21-19700 desoldering station performed very well for a low end, small project/hobby originated station. For larger projects, there are concerns about the frequency of cleaning with the built-in pump. I removed solder from about 20 pads before I had to clean the filters. At the end of my tests, I notice the tips of the de-soldering gun were very dirty. During use the tips should occasionally be wiped using a damp sponge, like those used by a solder station.
Part VI – The Spoiler (don’t read this if you don’t want to know)
Because the manual is so poorly written, my first step was to do check www.tenma.com, only to learn that, as mentioned earlier, Tenma is a global brand, owned and operated by Element 14, but of no really help for the desoldering station. NOTE: www.tenma.com is no longer a valid link and I have not found another.
Second, I ran a google search with much more interesting results. As it turns out, it seems that Tenma may not manufacture the station at all, but the Chinese-based Aoyue (www.aoyue.eu) does under a different model number (AOYUE Int 474A+). They also distribute the station through other distributors. Checking with Aoyue and other distributor’s support websites I was able to piece together other additional information that I share in the video under Part III – The Setup, Operation and Maintenance
One of the reasons I believe Aoyue may be the manufacturer of the station is the range of soldering and desoldering products they make. The manuals for the 2 station are almost the same. The desoldering gun is the same and made by Aoyue. What is interesting is that the Int474A and the older model of the Int474A+ is no longer available through Aoyue, the newer model Int474+ and the Int474++ are.
Older Models
Newer Models (w/o “cal” button”)
Please let me know if I missed something in the documentation. Also please pardon my typos.
Gordon Margulieux
Meridian, ID USA
