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Weller WXR 3 rework station - teardown


Six years ago I did a teardown of the Weller WR 2 rework station. Today I have its bigger brother on the bench for a teardown: the Weller WXR 3 rework station!

Weller WXR 3 specifications
[*]Temperature control: 100 - 450 .. 550 °C (range depends on tool)
[*]Airflow control suction: up to 18 l/min and a vacuum of up to 0.7 bar
[*]Airflow control blowing: up to 15 l/min
[*]Pick-up vacuum pump: up to 1.7 l/min and a vacuum of up to 0.5 bar
[*]Channels: 3 (up to 200 W per channel)
[*]Power consumption: 420 W (600 W)
[*]Dimensions: 273 x 235 x 102 mm (l x w x h)
[*]Weight: 6.7 kg[/list]

The WR 2 was the entry model in the rework station models. The top model was the WR 3M. The WXR 3 is the successor of the WR 3M. It is part of the newer Weller WX line and is not compatible with the hand pieces of the previous generation. By now the WX line has been around for over 10 years (2010) so even the WXR 3 (2014) is not exactly new.

One of the new features that was introduced with the WX hand pieces is the ability to store configuration data in the hand piece. Settings like temperature presets, offset and standby are saved to an EEPROM inside the hand piece. When the tool is connected to another output or even another soldering station, the settings are automatically applied. This is especially handy if you have more hand pieces than outputs and saves you setting the defaults each time you change a tool.

Another novelty is the usage of a motion sensor to detect whether the hand piece is in use to enter standby. This does away with special stands with switches or magnets and works even if you put the tool down on your desk (not recommended). It looks great on paper but is not worked out very well: The motion sensor is quite insensitive and picking up the hand piece may not always exit standby.

From the outside the Weller WXR 3 looks almost identical to the WR 3M. In my WR 2 teardown I wrote I did not like the size of the unit, but once you see the insides you'll understand the size. It's only a minor inconvenience because unlike many other devices, the Weller rework stations have a large, flat and sturdy top surface making it perfect for stacking other items onto.

It's not until after powering up that the differences with the previous generation become apparent: The 7-segment display was ditched for a backlit 240x88 pixels LCD. The standard display mode shows the current temperature of all three tools with a power bar on top and the tool name at the bottom. The alternative display mode shows only one output, but also includes the set temperature, quick temperature presets and additional info like a vacuum bar for the desoldering tools.


Made in Germany. Yeah! Unfortunately the sticker on the back says made in Mexico. Oops.

While the user interface got a graphical overhaul, operation sadly did not. Sure, navigating and configuring the settings is much easier with the graphical display, but switching an output on or off still requires pressing the up and down buttons simultaneously with immaculate precise timing. Even after many hours, I still frequently fail to switch on or off a tool from the first time. Just one extra on/off button would have made the user experience so much better. But I guess we can't complain. The rest of WX series got a horrid touch screen and click wheel.

Another change from the previous WR series I don't like is the omission of the LEDs above the outputs. These gave a quick indication of which channels were on and the blinking or solid green LED showed whether the tip was at temperature even out of the corner of your eye. Weller's vision was to replace the indicators with a LED ring in the hand piece. At first it looks a bit gimmicky, but it's actually a great idea. The problem is that several tools did not get the LED ring (WXP 90 soldering iron, WXMP micro soldering iron, WXMT soldering tweezers...).

Other than that the WXR 3 works as advertised and has plenty of power per channel: up to three 200 W hand pieces can be powered at the same time. I can't comment on the hot air pencil, but the pump offers plenty of suction for the WXDP 120 desoldering iron. Forget about solder wick or the Soldapult Deluxe! Desoldering stations like this one are in a completely different league... I'm also very impressed with the WXMT soldering tweezers.

Lifted the lid... Just as with the WR 2 the pump and huge transformer catch all attention. In fact, the transformer is even bigger than that of the WR 2 to cope with the power demands of the extra channel. I assume it is the same as that of the WR 3M.

The enclosure is the same as that of the WR series. Construction quality is quite decent with an all metal chassis and cover. Only the front is plastic.

The pump is also the same as that of the WR series: The label says Weller but it is a Thomas G 24/07-N rotary vane pump (model 50311 or 50220). It does look like a quality pump. Quite different from what you find in most Chinese rework stations.

The WR 2 had the pump's pressure outlet and vacuum inlet connected straight to the Air and Vac nipples at the front of the unit (which hold an air filter each). That means that whenever the pump was working, air flowed through both nipples. I never had two air tools connected at the same time so it never occurred to me, but in theory a desoldering iron with a very fine (or clogged) nozzle can prevent the hot air pencil from getting sufficient airflow. The WXR 3 (and WR 3M) solve this issue by including a solenoid valve between the pump and the nipples. That's why the tubing is more complex than in the WR 2. When sucking air (desoldering iron), it can vent via the valve to the inside of the unit. Similarly, when blowing air (hot air pencil), it can take in air from the inside of the unit through the valve. The valve is a Bürkert 6106 C 2.0 FKM PA rocker solenoid valve. The gold piece attached to the valve body is a silencer through which the air passes.

The toroidal transformer is a custom job for Weller by Noratel Germany AG similar to their RT300 series but with a higher power rating and 3 secondary windings. The transformer rates 420 VA with 230 V primary and 24 V / 2 A and 2 times 12 V / 15.5 A secondary windings.

Behind the transformer (right in the picture above) is a second pump that was not present in the WR 2 (but is in the WR 3M): The vacuum pump for the pick-up tool. Again there is no manufacturer indication, but I found the pump to be a Thomas WOB-L 8003 series piston pump. The exact model number is 80030638 but that model is not listed in the datasheet. It might be a custom job for Weller. Confusingly the label on the pump says 6 V DC while the motor has 12.5 V DC / 5500 rpm printed on it. Perhaps the pump is ran at half power to keep the noise or heat down? The vacuum pick-up tool really does not need much airflow.

Display and keyboard PCB:

There is very little to see on the display/keyboard PCB. I don't even see a driver chip for the LCD. It might be hidden behind the display, though.

One thing that is very different from the WR series is the main PCB. In the WR series it is mounted on the side and easily accessible. In the WXR 3 the PCB is sandwiched between the chassis and subframe. It is a pain to remove.

A closer look at the main PCB:

Unlike the double-sided PCB of the WR series, this is a 4-layer PCB. That makes it much harder to follow the traces visually.

The heart of the Weller WXR 3 is a PIC32MX460F512L-80I/PT microcontroller clocked by an external 8 MHz crystal. Just as with the Weller WR 2 and Weller WHA 900 I took apart earlier, there's an unmarked jumper connected directly to the microcontroller (at the bottom of the board, left from the transformer connector). I don't have the guts to test what it does.

Below the microcontroller is a Nexperia 74LVC4245A dual-supply octal tranceiver to allow the 3.3 V PIC microcontroller to communicate with the 5 V world around it.

Top right from the microcontroller are three Onsemi LM393 dual differential comparators of which I do not know the purpose. I'm losing the traces in the inner layers. It seems that at least some inputs are connected to the current monitoring ICs of the tool outputs.

Further to the right is an unused 6-pin header which is probably the programming interface.

Below the programming header are two COM ports for external accessories like a fume extraction unit, foot switch, board preheater or computer for remote operation or data logging. Each port has an Analog Devices ADM3251E isolated RS-232 line driver and receiver. Not all of the accessories actually support RS-232 communication, so each COM port can be configured in the menu to act as a simple switch input or floating switching output (via a Liteon LTV-356T optocoupler) depending on the attached accessory.

Below the COM ports is a USB port for firmware updates and importing configuration settings. The USB port is connected directly to the PIC microcontroller.

Below the USB port are the connectors for the pump (two PCB spade connectors slightly to the left), solenoid valve, vacuum pick-up pump and an unknown unpopulated 3-pin connector. Each pump is PWM-driven via an Onsemi FQD19N10L N-channel MOSFET. The solenoid valve is switched by a simple BC817-40 NPN transistor in SOT23 package directly above the connector. I don't know what the unpopulated connector is for. It too has a BC817-40 NPN transistor.

Moving to the left side of the PCB we see that each output has three Toshiba TPCA8123 P-channel power MOSFETs. Why three? Weller has three different types of tools in the WX line-up: 24 V tools like the WXP65 and most other classic non-cartridge soldering irons, 12 V tools like the WXMP active tip soldering iron, and 12 V tools with two heating elements like the WXMT soldering tweezers. Thus there are two 12 V MOSFETs and one 24 V MOSFET per output.

The WR 3M used a similar setup albeit with triacs instead of MOSFETs. Outputs 2 and 3 each had three triacs, but output 1 had an anomaly: It had an extra triac (four total) in order to support the HAP200 hot air pencil that has two 24 V heating elements. The successor of the HAP200 in the WX line, the WXHAP200, has a single 24 V heating element, so the WXR 3 no longer needs the anomaly in output 1. The WXHAP200 can be used on all three outputs.

Looking at the PCB above, each output has the three TPCA8123 MOSFETs in a triangular layout. The left MOSFET is for the 24 V tools, the top one for the 12 V heating element and the bottom one for the second 12 V heating element. Each heating element shares the same ground via a 10 milliohm current shunt. The current is measured by a SOT23-5 or SC70-5 IC at the left side of the PCB, but I can't identify it (component marking "SARB"). The same IC is used to measure the pump vacuum with the pressure sensor in the bottom left corner of the PCB.

As I wrote in the introduction, the WX hand pieces have an EEPROM and motion sensor built-in. Some tools have a LED ring and some have a push button. In addition the temperature reading of the tip is digitized in the hand piece itself. All this information is exchanged with the soldering station over an I2C bus. The I2C data lines of each output are connected from the output board via a ribbon cable to a NXP PCA9545A 4-channel I2C switch above the main microcontroller (the ribbon cable was disconnected for the picture). Just below the I2C switch is a SOT-23-5 Microchip 24AA04 I2C EEPROM.

The pinout of the output on the soldering station looks as follows:

The TIP pin connects directly to the solder tip on the hand piece. It is used for equipotential bonding. By default the Weller WXR 3 (and most Weller stations) connect the tip directly to the mains earth. With the equipotential bonding jack (bottom right corner of the PCB), you can choose different bondings like potential free (floating tip) or a different earth reference. Some hand pieces have TIP and GND connected, others keep them apart. I don't know why that is.

The choice of MOSFETs over triacs required another change from the older WR series: The triacs switched the transformer outputs directly, but (single) MOSFETs can't switch AC. A beefy bridge rectifier is formed by the four TO-220 ST Microelectronics STPS41H100C power Schottky rectifier diodes to convert the transformer AC into DC for the MOSFETs. The diodes are mounted through cut-outs onto a small heatsink at the back of the PCB, which on its turn is mounted to the metal enclosure.

Even though the transformer has a 24 V winding, the two 12 V windings are put in series to feed the bridge rectifier. With the center tap between both 12 V windings it is possible to get 12 V and 24 V DC for the MOSFETs. The 24 V winding appears to be used only for the pump and solenoid valve. There's a small bridge rectifier for the 24 V winding right above the two large electrolytic capacitors at the bottom of the PCB. Talking about the electrolytic capacitors... Samwha, again? In a device that retails well over $2000 I'd expect better quality electrolytic capacitors.

Right from the electrolytic capacitors is another LTV-356T optocoupler which, I think, is used to detect the zero crossing on one of the 12 V windings.

In the bottom right corner are two buck converters around a Texas Instruments LM25011 switching regulator which provide power for the low(er)-power electronics. I did not measure the voltages, but judging by the PCB layout the top one outputs 5 V for various ICs around the microcontroller. This 5 V is then converted to 3.3 V for the PIC microcontroller via an ST Microelectronics LD1117AV33 low-dropout voltage regulator. The bottom buck converter feeds several Microchip/Micrel MIC5201 low-dropout voltage regulators and, surprisingly, the vacuum pick-up pump.

In the top left corner is a CUI Devices CSS-J4D20 buzzer and this one puzzles me: I have never heard the station beep, nor are beeps mentioned in the user manual. I know the Weller WX 1 and WX(D) 2 beep with button presses and errors, and the buzzer can be enabled or disabled in the menu, but the same option is not present in the WXR 3 menu.

I/O that is exposed to the exterior, like the USB data lines or hand piece I2C bus, is protected against ESD with an ST Microelectronics ESDA6V1SC5 quadruple unidirectional voltage suppressors.

Finally a look at the bottom-side of the PCB:

That concludes this teardown. I hope you liked it!


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