858D Hot Air Rework Station

The 858D+ Hot Air Rework Station

The 858D+ is a cheap, if not the cheapest hot air rework station you can buy today. My first encounter with it was in EEVblog episode #167 [1] in April 2011 when Dave L. Jones reviewed his Atten 858D station (see embedded video at the end of this blog post). Now, early 2016, a myriad of clones are available through eBay and its Chinese counterparts. In this blog a quick overview of the 858D/858D+ hot air rework station.

Note: If you think of buying an 858D+, I recommend you read these threads on the EEVblog:

What is the 858D+ hot air rework station?

A hot air rework station is simply a tool that blows hot air at a controlled temperature. The hand piece has a heater and temperature sensor, usually a thermocouple. The controller unit uses the feedback from the temperature sensor to keep the temperature stable. The air flow is controlled with either a fan or a pump. Most hot air stations have the fan or pump inside the controller unit. A flexible tube goes from the controller unit to the hand piece carrying the air as well as the wiring for the heater and temperature sensor. An example is JBC’s JT Hot Air Station.
The 858D however has a blower fan inside the hand piece. So that part is a bit bulkier and additional wiring is needed to the hand piece. The way the 858D’s handle is made brings the risk of blocking the fan air intake with your hand when you hold it.
Be aware that while temperature can usually be set in increments of 1 degree, it might only be the top end manufacturers who actually achieve that level of control accuracy of the air temperature. Even then, it is only valid at a certain distance from the nozzle.

What do you use a hot air station for?

Hot air can be used for many purposes, but the name rework implies a specific application area. Hot air stations are handy when it comes to de-soldering chips from a PCB. Especially when the pads are underneath the chip (BGA, QFN and similar type packages), or when you have a large pin count QFP package. By heating the PCB and the chip all at once you have a good chance of de-soldering the chip without damaging the board.
You could use a hot air gun for soldering too. For example when you don’t have a reflow oven available but need to solder those ICs with pins underneath. Using solder paste and hot air you can get a fairly good solder joint. Some people have experienced good results reflowing BGAs this way. A warning though. In my opinion this is fine for hobby level electronics, but you lack the controlled consistency needed to guarantee long-term reliability.

A part in this video below shows how to solder a BGA chip with a hot air gun. (Starts at 35:00 and stops at 36:56):

Another benefit of a hot air gun or rework station is that you can use it for heat shrink tubing. You can finally get rid of lighters, matches, using your soldering iron or whatever trick you used before. Having a controlled temperature set to the correct level means you avoid overheating and damaging the wire’s isolation.

The 858D+: different brands, quality, and components

Atten, Youyue, Yihua, W.E.P., Scotle, Saike… If you do a search on the 858D or 858D+ hot air rework station you will find quite a few brand names for this tool. There is also a Mlink H1 [2], looking to be the same as the Youyue 858D+.
Who came up with the original design? Your guess is as good as mine. Whichever unit you choose, they all look the same and work in the same way. The differences between them are revealed only when you open the enclosure.
Most units have a single sided PCB with through-hole (THT) components. Yet the Youyue for example has a double sided PCB and a mix of THT and surface mount (SMT) components.The quality of soldering, wiring, and overall assembly varies but is mostly in the ‘just OK’ category. It seems to me that the Youyue has the best build quality of the different brands.
Each circuit and PCB differs ever so slightly between the manufacturers. At least three different microcontrollers have been found by members of the EEVblog forum: the Youyue 858D uses the Atmel ATmega8 [3]. Atten uses a Holtek micro instead [4]. There is also a controller found to be a Samsung.[5].

The pictures below show the differences between the PCBs of the YouYue 858D (top image) and my own unit, the Hylko 858D (bottom image):

Youyue 858D PCB

The PCB of the Youyue 858D. Courtesy of Robert Spitzenpfeil

Hylko 858D PCB

The PCB of the Hylko 858D

The Hylko is an example of a single-sided PCB. The circuit and layout have a few issues: there is a trace right below the optocoupler which decreases any clearance and creepage distances. In addition, the yellow X2-rated capacitor is used for the snubber. Instead on the Youyue’s PCB there is a red capacitor which is part of the snubber. The yellow X2-rated capacitor is placed across the heater’s terminals. The red knobs of the Hylko are missing in the picture: they don’t match to the switches and are loosely fit between the switches’ actuator and the front panel.

Third party modifications

Custom firmware for the ATmega microcontroller

Robert Spitzenpfeil a.k.a Madwom created custom firmware for the ATmega microcontroller in his Youyue 858D+. Since the PCB of the 858D+ lacks an in-circuit programming header he created his own adapter board. It fits right in the DIP socket.

Fan speed measurement mod

In addition to the custom firmware, Robert wanted a better way to determine the fan speed. He created small board to measure fan speed that fits on top of his ATmega adapter board.

Samsung to ATmega microcontroller adapter board

The custom firmware is written for the ATmega168, which is pin-compatible with the ATmega8 used by the Youyue. If you have a unit using a different microcontroller you are out of luck, unless it’s the Samsung. EEVblog form member wguibas has made an adapter board for the Samsung microcontroller. This means if your unit has that Samsung microcontroller, you can benefit from Robert’s firmware too.

Safety concerns – inspect your unit before use

When you buy an 858D(+) you know you are buying something that is built as cheap as possible. Still you do want it to be safe to use. There are reports of problems in this regard [6] [7] so if you buy an 858D+ or similar unit, be sure to execute the following checks before turning it on.

1 : Check if all exposed metal is connected to protective earth

  • Unplug the unit!
  • Take out your multimeter and set it either to Ohms or continuity mode.
  • Connect one probe to the mains plug earth pin
  • Probe the handle’s exposed metal parts for continuity to the mains earth pin. You should measure less than 1Ω.
  • If your unit uses plug and socket pair to connect the hand piece to the station, probe the connector’s metal parts too for continuity to mains earth.
  • Find a spot on the front panel, rear panel and top cover, to probe them for connection to mains earth. You might need to use force to penetrate the paint.
Measuring continuity to safety earth

Measuring continuity to safety earth

2 : Open the enclosure for a more detailed inspection

Safety earth connections

  • Unplug the unit!
  • Undo the screws: 4 in the corners of the front panel, 4 in the corners of the rear panel, 2 on each side of the top cover. Take the cover off.
  • Check if the mains earth wire has a solid connection to the enclosure at a dedicated point. Make sure the screw cannot get loose. The earth bond in the picture below is an example of bad design: no proper crimp, but two wires soldered into the lug. No shake proof washer but just one nut. Also no dedicated mounting point, but shared with the PCB.
  • Make sure the earth wire from the hand piece has a secure connection to the mains earth inside the enclosure that will not come apart.
858D earth wiring

Mains switch (top left) and earth bonding point (right screw)

Mains wiring

  • Check the connections of the mains input, the fuse holder and the front panel switch. The connections should be solid with no exposed metal. In my case there was a big blob of solder on the mains switch, almost shorting it (already removed before taking the picture); check for this kind of thing in your unit.
  • If your country uses a polarized mains plug: make sure it is the Live wire (not the Neutral) going to the fuse and the switch! (I live in the Netherlands and we use a non-polarized plug for AC mains.)
  • Open the fuse holder and make sure the fuse is indeed a real fuse. If there is a fuse in the plug check that one too. There are reports of fake fuses [8].
  • Inspect the wiring and connectors that mains and low-voltage wires and connections are kept apart. Make sure exposed metal parts can never touch each other.
  • Optionally: check the crimps on the wiring for proper contact and no loose wires.

Fan air intake

The mold for the hand piece parts could be better: in my unit the air intake has overmold and the slots are much smaller than they should be. This inhibits proper air flow. Nothing a screwdriver can’t fix, but check yours.

858D Hand Piece Air Intake

The air intake: top right slots are very tiny. Left-most column is after prying with a screwdriver

Dave L. Jones’ review and teardown of the Atten 858D

Sources

  1. Dave L. Jones, EEVblog #167 – Atten 858D Hot Air Rework Review, EEVblog
  2. Carrington, Youyue 858D+ some reverse engineering + custom firmware (Reply #74), EEVblog Forum
  3. Robert Spitzenpfeil, YOUYUE 858D+ hotair station — reverse engineering #1, My 2μF
  4. YouTube, EEVblog #167 – Atten 858D Hot Air Rework Review (4m53s)
  5. tjb1, Youyue 858D+ some reverse engineering + custom firmware (Reply #72), EEVblog Forum
  6. Tasman, DEADLY WIRING FAULT ; Atten 858D+ Hot Air Rework Station, EEVblog Forum
  7. Robert Spitzenpfeil, YOUYUE 858D+ hotair station — teardown, My 2μF
  8. alias_neo, Re: DEADLY WIRING FAULT ; Atten 858D+ Hot Air Rework Station (Reply #139), EEVblog Forum
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6 Comments

    • K-type indeed. Some manufacturers tell you, others don’t. I measured the thermocouple response of my unit confirming it is a K-type.

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