Tools upgrade: Hakko FX-951 soldering iron and more

R. X. Seger
Sep 19, 2016 · 10 min read

Proper tools are essential, on the other hand, it is a poor craftsman who blames his tools. In either case, I felt it was a good time to upgrade some of my tools for working with electronics — primarily the soldering iron, but also a few other miscellaneous parts including multimeter test leads, tweezers, knife, and solder. In this article I’ll cover what I upgraded to and from, then conclude with using the new tools to rebuild a prototyped circuit onto a printed circuit board (as shown in the image on the left).

This is only my experience, not necessarily the best advice. I recommend and was inspired largely by the recommendations in these videos:

although they have a slightly different focus: professional electronic engineering and electronic repair, respectively, whereas I am more of casual hobbyist. First let’s begin with upgrading multimeter accessories:

Multimeter leads

Much has been said about choosing a multimeter (see for example EEVblog #75 — Digital Multimeter Buying Guide for Beginners) but I happen to already own a Fluke 179, a solid product. However, the leads that came with the multimeter, as all stock leads, are too thick for fine electronics work.

Purchased the Ultra Fine Universal Probe Test Leads Cable Multimeter Meter 1000V 20A from Aliexpress, found from /r/electronics codeandsolder review espousing the leads as good yet cheap, shipped via China Post:

With the shrouded banana plug connector, unable to insert into a Fluke 179 multimeter with recessed female banana jack:

No problem, cut the shroud off with scissors, came off easily, then fit in:

Maybe not suitable for high-current but enjoying the finer point, conveniently reaches into breadboard holes. Measured 0.2 Ω resistance:


For holding small components, purchased the Wiha 44501 Stainless Steel Fine Point Professional ESD Precision Tech Tweezer with Static Dissipative Grip and Hypo Allergenic, 130mm Overall Length. Not inexpensive but has excellent reviews from a reputable manufacturer.

Testing unsoldering, worse grip than needle nose pliers, not unexpected so still keeping pliers in toolkit. These Wiha tweezers could be useful later for soldering miniscule surface-mount components.


The printed circuit board I’ll be using shortly was salvaged from another project which used less than a third of the space. Scored the board then snapped it over the edge of a table.

Used garden-variety scissors for scoring, but cleaned up the edge with a X-ACTO Z Series #1 Knife with Cap (XZ3601) (arrived later in the day):

Soldering iron

The old kit

Pro’s Kit 6PK-353A Economy Solder Station, a cheap station with 20W/40W selectable wattage. Oxidized tip, could replace the chisel tip but it is about time to replace it with a better unit.

Analog or digital?

Dave Jones in EEVblog #180 Soldering Tutorial recommended the Hakko FX-888, or other well-known brands including Weller, Metcal. The analogue FX-888 is no longer manufactured, the replacement is digital: Hakko FX-888D Digital Soldering Station. The temperature control and other settings are adjustable via a pushbutton interface.

Not a fan of the digital interface, with a cumbersome button user interface replacing the intuitive analog temperature control dial. Apparently I’m not alone: A petition to bring us back the knob!? A complaint to modern soldering stations.

What about getting an older analogue model? There were some appealing offers on various websites, but then I learned Hakko is the most cloned soldering iron brand in the world. Some of the clones may be acceptable, others could be inferior or dangerously unsafe; not risking it.

Nonetheless, even with the poor UI, hopefully adjusting temperature control should be rarely rare so it is not that big of a deal. So I gave in to digital.

Hakko FX-951

It is perhaps overkill for my purposes, but went with the Hakko FX951 Soldering Station with Chisel Tip Pack T15-D08/D12/D24/D32/D52. The FX-951 doesn’t usually come with tips, as there are many to choose from, but this one comes with a set of useful chisel tips.

What’s the difference versus my old iron? The Pro’s Kit had adjustable wattage, but no “temperature” control otherwise. With the Hakko you input the desired temperature and the tip temperature is regulated.

Louis Rossmann: The tools I use and why I bought them also recommends the FX-951, reinforcing my purchasing decision.

Soldering iron tip selection

There’s a wealth of soldering iron tips available from Hakko. For the FM-2027 handpiece included with the FX-951, in NA/EU, the T15 series is used.

Previously I bought a 99¢ copper tip on Aliexpress Lead-free Red copper Pure cupper Solder tip 900M-T-I For Hakko 936 FX-888D Saike 909D. Solid copper instead of iron/chrome plating, no integrated heater. Intended for the FX-888D, fits in neither Pro’s Kit nor FX-951. Comparison vs the old Pro’s Kit damaged heavily used tip:

Compatible tips from jwelectro’s Hakko FX-951 Soldering Station review:

T15 tips come in plenty of exotic shapes, but shape D aka the chisel tip is most general-purpose:

The kit I ordered came prepackaged with:

  • T15-D08: 0.8 mm chisel tip
  • T15-D12: 1.2 mm chisel tip
  • T15-D24: 2.4 mm chisel tip
  • T15-D32: 3.2 mm chisel tip
  • T15-D52: 5.2 mm chisel tip

If I was to order all over again, I may have gone with the Hakko FX-951 Soldering Station with a T15-D16 1.6mm Chisel Tip kit instead, slightly cheaper with only one tip, and the 1.6 mm T15-D16 appears to be more common. Going to use a chisel tip for sure, but what dimensions?

EEVblog #180 — Soldering Tutorial Part 1 — Tools recommends about a ~2 mm tip for most soldering, or smaller. Of what I have, could go with either the T15-D12 (1.2 mm) or T15-D24 (2.4 mm). Trying the T15-D12 first.

Assembled the iron, inserting the tip into the sleeve then the sleeve into the handpiece, threaded through the heat-resistant pad, then plugged into the station. Turned it on, greeted with a piercing buzzer sounding and the display showing “S-E”. The manual says to check the tip is inserted correctly and to measure the resistance, should be 10 Ω ±. Measured at 8 Ω.

Double-checked the tip. Need to plug it into the sleeve until it clicks, then it works. Turn on, heats up in a few seconds! Melts solder quickly:

Very quickly, nearly instantaneous compared to the old Pro’s Kit iron.


By default, at the factory the preset temperature is set to 750ºF. Yes, fahrenheit, though the manual online said 350ºC was the default. I kept it at this temperature for now. The FX-951 is 75W (70W to the iron), compared to 20W/40W selectable wattage on the Pro’s Kit. 400–840ºF (200–450ºC) temperature range with ±9ºF (5ºC) temperature stability per the manual.

Beeps: when the iron is placed into its holder, it will go into sleep mode, cooling off to a lower temperature, and when removed it will heat back up again in a few seconds. The station will beep when it heats up to the set temperature.

This is really annoying. Fortunately, Hakko released a firmware update to allow disabling the beeping: Additional Parameters to Mute FX-951 Alarms:

As a result of customer feedback, the firmware of the Hakko FX-951 Soldering Station has been improved to include two new parameters as outlined above.

The firmware is not user-updatable, but FX-951’s with serial numbers greater than 0005951208012611 include this option, mine did. “Alarm for at set temperature” is parameter #6. To edit the parameters, followed @jwrelectro’s instructions:

  • power off the unit
  • insert the control card
  • hold up and down buttons while powering on
  • press * to advance to next parameter until reaching 6
  • press down to change P6 from 1 to 0 (off)

No more temperature alarm, much better.

The use of a “control card” to change settings is slightly awkward, but it is more intended for use in a factory where an engineer sets the settings and the technicians are not supposed to change it. For home use, I am keeping the card inserted most of the time. It is nothing more than a piece of plastic to trigger an internal optical sensor, jwrelectro 3d-printed his own. Anyways, moving onto solder.


Upgraded to Multicore/Loctite 3096525-M 60/40 0.48 mm solder from some old RadioShack 60/40 diameter 0.062" (1.5748 mm) solder. The new solder is much thinner:

but noticeably more noxious. Not that you want to breathe solder fumes anyway, but it was motivation enough to turn on another fan to blow away the smoke. Proper ventilation is essential. Maybe a solder fume extractor. For now using a household fan similar to this Honeywell:

and a fluorescent desk lamp with flexible neck for visibility. The household fan works decently well, but does not precisely direct the airflow into a receptacle like a proper exhaust fume would.

Solder paste: No Clean Lead Free Low Temperature Solder Paste 15 Grams. Keep refrigerated. No reflow oven or hot air station yet, but wanted to get familiar with solder paste; haven’t used yet, sticking to solder wire.

Application: reconstructing the h-bridge circuit

To put these new tools to the test, took the sky-wired circuit from Building an H-Bridge from a salvaged Uninterruptible Power Supply and soldered it on a perforated RadioShack circuit board. Unsoldered new components from the old surge protectors, the salvaged gift that keeps on giving. This was much easier with the Hakko FX-951 compared to the Pro’s Kit 353A, the tip providing a flat undamaged surface, maintaining temperature consistently.

Although a relatively simple circuit, time spent including redesign, desoldering, soldering, troubleshooting estimated about 4 hours, a good test of using these new tools in a practical application for a serious project.

First soldering the bipolar junction transistors:

and the reverse:

Wiring up all the transistor drivers, using a breadboard-style layout:

Slightly modified the circuit, using only a 1 kΩ pull-up resistor on the NMOS NOR gate, and pulling it up to +5V instead of +3.3V to avoid having to wire both voltages to the circuit — this is safe since the output is only used to drive the BJT transistors, not fed back to the 3.3V-only Raspberry Pi GPIO, and the GPIO output with +3.3V high is acceptable as input.

For comparison, the old ugly sky-wired circuit:


New board soldered, had some difficulty with the single-sided PCB pads dismounting — for future projects, should try lowering from 750ºF to 600ºF, and go faster — still have a ways to improve my soldering skills but it works:

Tidied up the interconnects using a 7-pin cable I had with 6 wires (there was one missing presumably for keying):

  • 1, red: +5.0V
  • 2, not connected
  • 3, blue: control signal D
  • 4, black: ground
  • 5, white: control signal C
  • 6, brown: motor+
  • 7, gray: motor-

A lot cleaner, isn’t it?

This board connects to the breadboard and tray motor as follows:

And the completed board in action:


Updated schematic available:


The difference between the old and new soldering iron is night and day. The tip heats up before I know it, maintains the temperature constantly, and the high-quality chisel tip provides precision working on small components. This Hakko FX-951 was my first soldering iron with regulated temperature control, now that I’ve experienced it, no going back to an uncontrolled iron.

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