Review - Teardown: STAR  - MAPLIN (OEM) digital soldering station - Page 1
Forum section: electronics / general

author: ciccio
author_rank: Frequent Contributor
timestamp: July 27, 2011, 01:54:28 pm
content: STAR LU3204-00 low cost digital soldering station – review and teardownThis station is a low cost (about 50 euros) digital soldering station.It was bought when we had to set-up one additional workbench for a visiting engineer, and now it stays in my home lab.It's a Chinese OEM product, that I've seen sold under different brands and case color.Mine is black , labeled STAR electronics (Italy), model LU3204-00, but in the UK you can buy it from Maplin, model N16CH:http://www.maplin.co.uk/48w-lcd-display-solder-station-98133A similar model (with the same display and electronic, but without presets, is sold by Velleman :http://www.vellemanusa.com/us/enu/product/view/?id=522851and by others (RS sells one with it's label for a very higher price).Once I found the manufacturer, a reputable Chinese company, but I've lost the name and the site's address.The station body is rather small, fitted with anti-slip feet, and has a clear LCD display (12 mm digits) showing both actual and set temperatures, complete with operation indicators:HEAT when heating, WAIT if temperature is some degree lower or higher than the set point, °C or °F.The mains cable is fixed to the unit, and the exit is not on the rear, but on left side, making it really uncomfortable on the bench, so I promptly opened the case and installed an IEC power inlet on the rear and, at the same time, wired a green power ON LED (you can see two red/black wires in the photos) because you can tell the station is on only by looking at the LCD, and after the first day of use I forget it on for one week…(I believe having seen a similar one with an illuminated LCD, but I'm not sure)Actual use is really intuitive: a button for C/F selection, two buttons (UP and DOWN) to change the set-point, three (almost un-useful) buttons for preset temperatures (200 – 300 - 400 °C).There is an internal buzzer that alerts if the unit is switched on without a stylus connected, but remains silent if the heater is open…The stylus is a 48W, low voltage (24V), not too big and really comfortable to hold. The cable is about 110 cm long, rather flexible (it's shorter and stiffer than my Weller's, but the price is about 70% lower).The supplied tip is a conical one, rather small, but other tips are available, at about 3-4 euro a piece. The tip is made of magnetic metal (maybe iron) coated with a grayish finish and with a tinned point.The heater of the supplied stylus died after about 2 weeks, and I discovered that the heater was a special order spare part (at least for my supplier) , but I got a new stylus for about 10 euros.Removing the tip of the first stylus showed a cylindrical "gasket" made of sheet metal, and a lot of metallic "dust" that was released by the tip (see photo).Don't know, but I fear that these tips will have a very short life, by corroding themselves from the inside.The stylus holder "feel" was "cheap": made from plastic, with only a sheet metal shield to protect the hot stylus, it was sliding all over the bench top, making difficult to insert the stylus.I could have changed it with another, but decided to modify it adding an U-shaped piece of aluminum riveted to the underside, fitted with 4 anti-slip feet.When I disassembled the main unit, I checked the wiring, and found it to be neat, well made and complying with safety regulations.Tip and stylus connector are grounded to the mains cable ground.There is a fuse holder on the rear panel.The power transformer is of adequate size, incorporating a thermal fuse, and does not becomes too hot in actual use.The controller board is dual side, using mostly SMD parts.The bigger chip is one HOLTEK HT1621B (LCD driver)Next to it one ATMEL AT89C2051 8 bit microcontroller, and the smaller two are one ATMEL 24C024 (I believe it's an EEPROM, but I'm not sure: could not find it in ATMEL site), and one LM358 dual op-amp.The board shows some signs of "afterthought", like a tantalum cap added "on the air".In use, the low power of the stylus was detected only at first start-up, needing about 65 seconds to reach 300 °C. A moderate (10 °C) overshoot was noted, but only at start-up.The tip temperature was displayed accurately, with only 3-4 °C of error, but only at steady state. The sensor is far form the tip, so you can cool the tip (by touching the wet sponge), and the real temp is shown decreasing only after many seconds of delay.I don't understand why the temperature control algorithm is limited to a simple ON/OFF: with that microcontroller it is possible to write the code for a more efficient type of control (I don't ask for a PID, but at least a PD).By summing up: a nice, decently made unit, manufactured to good quality and safety standards, that operates correctly , for it's price.I tested it in our small production environment, and I found that the productivity (number of good joints per hour that can be made) of this tool is comparable to one of our older Weller units. I could even solder some SMD parts.For hobby or semi-pro work, it could be a bargain…

author: Bored@Work
author_rank: Super Contributor
timestamp: July 27, 2011, 04:24:19 pm
content: Quote from: ciccio on July 27, 2011, 01:54:28 pmIt is a Zhongdi ZD-937http://www.china-zhongdi.com/tcss01.htm

author: saturation
author_rank: Super Contributor
timestamp: August 01, 2011, 08:45:13 pm
content: Thanks for the good review. What is the heating element made off? Wire, or ceramic?The tip is most concerning, at least by the photo. That black carbon like material, if it keeps recurring and coming out of the iron handle suggests something in the tip is akin to pig iron, and can 'weep' burnt black carbon dust as its heated. Its conducts heat poorly compared to copper tips coated with iron.http://en.wikipedia.org/wiki/Pig_iron

author: ciccio
author_rank: Frequent Contributor
timestamp: August 02, 2011, 05:26:55 pm
content: Quote from: saturation on August 01, 2011, 08:45:13 pmThe heater (and the sensor) was inside a white ceramic tube, but I don't know how it's actually made (real ceramic heater or nicrome wire wound over ceramic?)

author: saturation
author_rank: Super Contributor
timestamp: August 02, 2011, 06:22:40 pm
content: Thanks so much ciccio for the reply. Are the tips you pictured hollow inside, and the heater is inserted into it or are the tips a solid piece of metal and the heater just conducts by touching the bottom of the tip?Quote from: ciccio on August 02, 2011, 05:26:55 pm

author: ciccio
author_rank: Frequent Contributor
timestamp: August 03, 2011, 05:23:34 am
content: The heater is inside an hollow metal tube (maybe steel, with a shiny chrome-like finish) connected to the handpiece's body via a disk and three screws (with spacers to create an empty space to keep the handpiece cool. (similar to old Weller's)This tube is inserted inside the hollow body of the tip, but there is a thin sheet metal "tube" (a foil of thin metal rounded to form a "C" section "tube") interposed between the two,maybe to help for thermal transfer.I think it has this form to allow thermal expansion (the "slit" will become narrower) while, at the same time, maintaining a better thermal contact with the tip, even when the tip expands with heating.I have an old JBC iron that has a similar construction, with an hollow tip heated from inside, and they cut a slit in the tip, with an external spring to maintain thermal contact.http://www.jbctools.com/classic-series/classics-products/soldering-and-desoldering-irons/pencil-soldering-ironThe Chinese solution is really "elegant": thumbs up!!!Another tube-shaped part covers all the above, and is screwed to the handle via a knurled cylinder (same than the old Wellers)Total tip lenght is about 65 mm. Outer diameter is 7 mm, with a 6 mm hole, 45 mm deep (the tip is very thin, in it's hollow section).In this moment I have no time for taking photos, but if you want I'll post them later.Regards

author: FreeThinker
author_rank: Frequent Contributor
timestamp: August 03, 2011, 01:47:58 pm
content: Quote from: BoredAtWork on July 27, 2011, 04:24:19 pm100% correct B.A.W. Here is the Operators handbook and circuit diagram.

author: saturation
author_rank: Super Contributor
timestamp: August 03, 2011, 03:38:13 pm
content: Thanks ciccio. It reads like this is a good functional soldering iron, beyond ergonomics the only thing to find out is its thermal performance. As you've mentioned before, it would be good to know how accurate the displayed station temperature is versus what the tip temperature really is, and how quickly tip temps recovers when cooled down.Thermal recovery: you've mentioned it takes 65 sec to go from ~ room temp to 300C.Tip accuracy: if you have some eutectic solder around, you could adjust the temp setting to the melting point of the solder and see where the solder melts; that would mean the tip is effectively at that temp. It would consider heat losses from radiation by the sheaths, poor conductivity, etc., which the thermocouple may not take into account. I've used SnCu0.7 at 227C and it a quick check, as the lower end of the Hakko 936 range is 200C.As a comparison for a benchmark, the Hakko 936 I confirm goes from room temperature 227C in 20 sec, 300C in 26 sec and to 400C in 43 sec, and if calibrated the analog dial represents the tip temperature as written.Last question, do the hollow tips have copper inside ?

author: ciccio
author_rank: Frequent Contributor
timestamp: August 03, 2011, 07:31:25 pm
content: Quote from: saturation on August 03, 2011, 03:38:13 pmI'll try to analyze the tip's structure and will post an answer ASAP.In my home lab, where actually I've placed the station, I found that I don't have a magnet (for checking if the bit is magnetic) or a tool suitable for scrubbing the inside of the bit (to reveal it's nature)...Regards

author: saturation
author_rank: Super Contributor
timestamp: August 05, 2011, 05:18:50 pm
content: Thanks ciccio, no worries. If you look down and shine a light down the bottom end of the tip you should be able to see a different color material sheathing in the core separate from the external color of the tip, you won't need special tools. Since good tips use copper cores its not unlikely to be any other material.Quote from: ciccio on August 03, 2011, 07:31:25 pm

author: binbags
author_rank: Newbie
timestamp: May 30, 2012, 08:27:59 am
content: Quote from: ciccio on July 27, 2011, 01:54:28 pmHi CiccioA little help from you if you can. I have the N16CH which has gone faulty on me. What I require is some data on the special lcd that this station uses. Can you or anybody reading this forum identify the pin out of the display used. It is a 22 pin device, 11 pins each side. for example which pins are the "com0,1,2,3 then "Y1--- to Y18. I know that I can apply some logic to find out, most DIL ic chips are pin 1 at the lower left corner with the legend reading from left to right, but I may be wrong. So any help from you guys would be great.

author: T4P
author_rank: Super Contributor
timestamp: May 30, 2012, 08:43:23 am
content: ... Actually the key thing that makes me look at zhongdi stations in disgust are the poor quality of many of their stuff ( many being weller clones too )and very short life of their irons ... tips short and something weird, heater as you said broke within a week and on top of that the iron looks like a standard wall plug iron ...I'll stick to my better built 936 clones

author: Martini
author_rank: Regular Contributor
timestamp: April 12, 2016, 09:25:49 pm
content: I know it's an old topic but I assumed it would be better to group the information about the ZD-937.In the pdf, I didn't see a word about the calibration. Is it possible to do it?