Micron Soldering Station Clean and Repair (T2440)

Summary
This blog covers the cleanup and minor repairs to an original Altronics (T2440) 60 W Micron temperature controllable soldering station.

Repaired and Cleaned Micron Soldering Station

Details
Purchased many years ago, the only repair or maintenance performed on the soldering station has been the replacement of the soldering iron element.

Since some of the plastic insulation around the mains power and handpiece cables was looking neglected, it was decided to perform a routine cleanup and repair of the unit.

Micron 60 W Soldering Station

Following the removal of loose dirt, the soldering station was disassembled. Four plastic screws secured the lid on the soldering station. Three plastic screws secured the heating element in the handpiece.

Disassembled Micron Soldering Station

The damaged cable from the soldering iron handpiece was cut off at the entry point into the soldering station.

Damaged Cable Entry Points

 
Isopropyl alcohol was used to clean the outside of the handpiece and connecting cable. The black plastic at the entry of the handpiece had become brittle and was replaced with two layers of black heat shrink.

Heater Element and Cable

Both the soldering element barrel cover and soldering tip were polished using a light cutting compound on a buffing wheel.

Heater Barrel Cover (Before)

Heater Barrel Cover (After)

Soldering Tip (Before)

Soldering Tip (After)

 

A bath of white vinegar (5 % solution) was used to clean the top case and soldering iron stand. These items were left to soak overnight.

 

Replacement of the black plastic around the handpiece cable was again made with black heat shrink.

Repaired Soldering Handpiece

The repaired handpiece was wired back into the soldering station.

Soldering Station Control Board

For the main cable, this was replaced with a newer style plug. Black heat shrink was fitted around the main cable at the entry point into the soldering station.

Replacement Mains Plug

The mains plug and cable were rewired into the station. As with any mains wiring the typical disclaimers and directions apply; be careful!

Rewired Mains Connection

 

Any remaining small items were firstly cleaned in an ultrasonic bath which was followed up with a liberal application of Isopropyl.

Large items such as the yellow/cream cover for the soldering station required hand cleaning with a general-purpose paste type liquid cleaner. This was required to remove ingrain flux, dirt or other burnt miscellanea.

The soldering station was reassembled and tested.

Operating Soldering Station

Soldering Iron Tip Holder (3D Printed)

Summary
This short post provides the file for a 3D printable version of the tooltip holder created in a previous post.

3D Printed Soldering Iron Tip Holder

Details
The file in the Downloads section below is a close representation of the wooden tool tip holder. Fusion 360 was used to draw the model; available on request.

Soldering Iron Tip Folder Model

Verification of the model was performed by converting to GCode and printing on a 3D Printer (Ender 3) using PLA with a 10 % fill, no bed adhesion and default wall and base thickness. The printed dead weight of the tooltip holder may be too light for some users; an additional weight on the base may be required.

Downloads 

Soldering Iron Tooltip Holder (STL)

Soldering Iron Tip Holder

Summary
This blog covers the build of a soldering iron tip holder using demolition site lumber.

Soldering Iron Tip Holder

Build Process
For the build, a piece of lumber (Jarrah) was salvaged from demolition scrap several months ago.

Demolition Site Salvaged Lumber

Without access to a lathe to create the required shape, a 64 mm diameter hole saw was utilised to create the round shape of the holder. The hole saw was drilled from opposing sides of the lumber to achieve the necessary depth.

Holder Cut by Hole Saw

Sanding of the holder was performed with 120 Grit on a belt sander then followed by 240 Grit on an orbital sander. The finished diameter of the holder was around 60 mm and the height was 72 mm.

Sanded Soldering Iron Holder Form

A paper template was printed to assist in locating and marking positions for the Hakko T-12 type soldering iron tips. The six positions could be increased to eight or ten without overcrowding.

Holder with Tip Position Template

Holes for the soldering iron tips were drilled with a 6 mm bit to a depth of 35 mm. The shaft diameter of T-12 tips is marginally larger than 5.5 mm.

The central hole created by the hole saw was glued and plugged with a wooden dowel.

Holder with Six Drilled Tip Positions

After the glue had cured, the dowel was finished flat with the surface of the holder. A 16 mm Forstner bit was drilled to a depth of 35 mm. The 16 mm diameter of thr bit suits Stannol PCB flux pens.

Holder with All Drilled Positions

All the holes were deburred with a 5 - 10 mm countersinking bit and the holder given a final sand.

Three coats of primer (Rust-Oleum flat white Primer) were applied to the holder with sanding using Grade 000 steel wool between each coat. Rolled sandpaper was used for the drilled holes. 

Holder with First Coat of Primer

For the final colour of the holder, Rust-Oleum Blue Diamond was chosen. The colour was applied in three coats with sanding using Grade 000 steel wool after the initial two coats. A fine bristle paintbrush was used to paint inside the holes.

Holder with Final Coat of Paint

Shown below is the soldering iron tip holder with tips and flux pen mounted.

Holder with Tips and Flux Pen

 
Summary
While the primer and colour spray paints achieved a descent finish, for longevity of the holder a harder two-pack or epoxy-based paint may be preferred.

PCB Solder Jumper Pads

Summary
This blog summarises the tests performed on a selection of Printed Circuit Board (PCB) solder (bridge) jumpers. PCB jumpers are frequently found on PCB's used in electronic equipment. For testing, jumpers were reproduced on a single PCB in various sizes for comparison and testing purposes.

Solder Jumper Test PCB

Solder Jumper
The PCB solder jumper electrically connects two, or more, separate circuits. The function of the solder jumper performs is as varied as the type of jumpers seen on electronic equipment.

Solder Jumpers on LCD PCB

Solder Jumper Design
Some of the early solder jumper designs were novel as two or more pads places relatively close to each other, consider an 0201 style footprint. Either a blob of solder, a soldered zero-ohm link or a short piece of wire was required to join adjacent pads.

Some websites have entire pages dedicated to PCB jumpers for CAD packages such as Eagle.

Example Eagle PCB Jumper Design

 

The technique of using two pads is still widely used however, there have been some variations to the solder jumper design. For example, the forum posts on DIP Trace show four alternative jumper designs.

Changes in the solder jumper design have been a result of improving manufacturability, reliability when reworking the jumper and in some instances a general reduction in the footprint size.

For example, changing the two side by side pads, think of an 0201 resistor, to a chevron (arrow) or pad in pad can increase the mating area between the two solderable surfaces. An increased surface area can result in a better chance of solder adhesion. The adhesion can be important for boards that are run through reflow soldering.

Solder Jumper Prototyping
Some of the PCB jumpers depicted in this blog were replicated on a test panel. The focus of the prototyping was for small to miniature solder jumpers.

Unsoldered Jumper Test PCB

Only J11 has a minimal solder mask between the jumper pads.

PCB Arrow Jumper

J1 and J2 represent the arrow jumper which was created in a nominal and miniature size.

 

PCB Tongue and Groove Jumper

J3 and J4 represent the jumper design seen on portable/wearable electronic equipment. Two very small jumpers were created.

 

Various Ball and Socket Jumpers

J5 through J10 were designs similar to those presented on DIP trace with a few personal variants using a pad inside a pad.

Large Small Pad Jumper

J11 was a design mentioned on an Engineering blog where a larger pad with more solder was more likely to bridge to a smaller pad.

Side by Side Pad Jumper

J12 was a common design used by the Open Source forums for Arduino shields, OLED or LCD boards.

Dual Round Pad Jumper

 J13 was created to test round pads side by side.

Four Pad Jumper

J14 was inspired by the LCD to test a variant of inward facing arrows.

Testing Solderability
A 1.2 mm chisel tip (Hakko T12-D12) with lead-free solder was used to bridge the solder jumpers. As shown in the image below, not all jumpers (J2, J4, J11 and J13) would bridge using the chisel tip.

Chisel Tip Soldered Jumper Test PCB

The same chisel tip was used to remove the solder bridges. For most of the solder jumpers, the solder was removed in one pass. All jumpers were tested for continuity, none were shorted.

Chisel Tip Desoldered Jumper Test PCB

For a second test, a 1.0 mm 45 degree conical tip (Hakko T12-BC1) with lead-free solder was used to bridge the solder jumpers. Again not all jumper (J2 and J4) would bridge with the conical tip.

Conical Tip Soldered Jumper Test PCB

Desoldering jumper with only the 1.0 mm conical tip was time-consuming due to the small amount of solder removed in each pass. Desolder braid was required to remove enough solder from the jumpers in a single pass. Alternatively using a 3.0 mm 45 degree conical tip (Hakko T12-BC3) allowed cleaning of the jumpers without desolder braid.

As a third test with reflow soldering, solder paste (NC 254 SAC 305) was applied to the PCB manually.

Solder Paste Application on Jumper Test PCB

The result of the reflow process was that the smallest solder jumpers, J2 to J4 and J11 and J13 formed a bridge. Any soldering iron tip could be used to remove the bridge. Larger pads did not bridge likely due to the pad size and small amount of solder paste.

Reflow Solder Result on Jumper Test PCB

Summary
For testing in this blog, soldering iron tips in the form of chisel, conical and different 45-degree were used.

Using the metrics of solderability and ease of desoldering, jumpers J5, J7 and J12 worked with all the types of soldering iron tips.

The smaller jumpers, J2, J3 and J13 required a small tip for reliable production of a solder bridge during hand soldering.

Jumpers J4 and J11 did not solder reliably using hand soldering however reflow soldering was successful in all three attempts.

Larger jumpers J1 and J4 together with the multi-pad jumper J14 required larger soldering tips for creating the solder bridge. These jumpers were not tested extensively with reflow soldering.

Some of the jumpers detailed in this blog are found in hobbyist or consumer equipment with each designed to suit their application.

To suit the home hobbyist, jumpers J1, J5 or J12 would be ideal choices.

Finally, a note concerning PCB production. The smallest jumpers with small pads and 0.1 mm pad to pad spacing significantly increased the cost of the PCB; a salient point when moving to miniature or high-density PCB designs.

Downloads
Gerber files downloadable using the link below.

Jumper Gerber Files

Failing B22 E27 LED Bulbs

Summary
This blog reviews E27 or B22 style LED bulbs and the heat produced during operation.

LED Bulbs
In many mains powered LED bulbs a non-isolated, AC to DC LED driver is central to the design. For some bulbs, the Printed Circuit Assembly (PCA) containing the LED driver is separate from the LEDs. The LED Printed Circuit Board (PCB) is usually metal backed to assist in heat dissipation. Both the LEDs and driver assemblies generate heat however the majority of heat is generated by the LEDs. 

Failed LED Bulbs
After several LED bulbs failed across a period of weeks whilst daytime temperatures were high, the bulbs were opened for investigation. A failed Surface Mount (SMT) LED on the PCA was easily identified by black dots. Other LED bulbs had failed controllers.

Single Failed LED (Black Dots)

LED Testing
The LED driver on the bulbs was identified from the manufacturer Bright Power Semiconductor. The manufacturer datasheet detailed the LED driver‘s single string capability was 120 mA with a maximum string voltage of DC 72 V.

Based on the driver string voltage, current with the dimensions of the LED in the bulb, the LED manufacturer appeared to be Everlight however this is not substantiated.

Using the specifications of the Everlight LED as a reference; a forward voltage of 9.15 V and 100 mA maximum current, a single LED board was left on the board. The single LED was powered from a benchtop power supply and measurements were taken.

For a constant current of 100 mA, the forward voltage was approximately 9.1 V. Measuring the temperature of the single LED after 15 min showed the case temperature of the LED reached 85°C mounted against the metallised board.

Temperature of LED Case

The rear of the metallised board reached nearly 40°C in the open air. When installed in the bulb, the temperature of the metallised board is expected to be higher considering the enclosed space.

Temperature of LED Rear Side

 
Changing the power supply to constant voltage mode with a 125 mA current limit, several measurements were performed at different voltages. Temperature measurements were also performed with a 26°C ambient. The graphed results are illustrated below.

LED Temperature vs Forward Current

Summary
During the testing process in this blog, a maximum LED case temperature of 101°C was measured with an ambient of 26°C.

Highest LED Temperature

It should be noted that many LEDs will operate continuously with a junction temperature at or above 100°C. Manufacturer datasheets usually provide graphs showing luminous flux changes with temperature which help determine derating performance.

The derating of luminous flux versus temperature varies considerably between LED manufacturers. For the LED described in the blog, which was suspected to be manufactured by Everlight, the maximum junction temperature was 115°C. The derating curve to 115°C is shown below.

Everlight Luminous Flux vs Temperature

Using the bench tests results from this blog, it would be anticipated that with all LEDs active and an ambient temperature over 40°C, the LED junction temperature would exceed the datasheet rating. 

LED Bulb Driver and LED PCA's Showing Heat Discolouration

Interestingly many over the shelf LED bulbs do not detail maximum operating temperatures on their packaging or datasheets. For the LED bulb described in this blog, the high generated temperature was likely a contributing factor to the reduced lifetime of the bulb.