Posts Tagged Repairs

MPCNC Drag Knife Holder: Lock Screw

While calibrating the MPCNC’s probe camera offset for the drag knife holder, this happened:

Drag Knife - vertical escape
Drag Knife – vertical escape

Well, at least it’s centered on the target:

Drag Knife - vertical escape - detail
Drag Knife – vertical escape – detail

This happened a few times before, because my fingers don’t fit neatly inside the drag knife holder to tighten the lock ring:

Drag Knife - LM12UU ground shaft - assembled
Drag Knife – LM12UU ground shaft – assembled

[Update: The lock ring keeps the holder at a fixed position inside the 12 mm shaft and doesn’t affect the blade directly. When the ring works loose, the threaded holder can rotate to expose more blade and, in this case, stab deeper into the target. ]

So I turned & knurled an aluminum ring, then tapped a 3×0.5 mm hole for a lock screw plucked from the Drawer o’ Random M3 Screws:

Drag Knife - lock screw - side
Drag Knife – lock screw – side

A view looking along the screw shows a bit more detail around the spring:

Drag Knife - lock screw - front
Drag Knife – lock screw – front

The general idea is to set the blade extension, then tighten the lock screw to hold it in place, without relying on the original brass lock ring, shown here while cutting a boss for the spring:

Drag Knife - turning spring recess
Drag Knife – turning spring recess

The lock screw’s knurled handle just barely kisses the NPCNC’s black tool holder ring, so my guesstimated measurements were a bit off. Clamping the knife holder one itsy higher in the tool holder solved the problem.

I cranked on 300 g of spring preload and, squashed like that, the spring’s rate is now 75 g/mm. Cutting at Z=-1 mm should suffice for laminated paper slide rule decks.

The original sizing doodle:

Drag Knife Holder - lock screw ring doodle
Drag Knife Holder – lock screw ring doodle

The short 18 mm section clears the inside of the LM12UU bearing, although it could be a millimeter shorter. The 19 mm section comes from the 3/4 inch aluminum rod I used, skim-cut to clean it up.

If I ever remake this thing, it needs a major re-think to get all the dimensions flying in formation again.

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Baofeng Bike Helmet Headset Wiring Repair

The audio output wire from the Baofeng UV-5R to my bike helmet headset adapter broke after a year and a half, far longer than I expected:

Baofeng - broken spkr wire
Baofeng – broken spkr wire

It’s the green one, over on the left, pulled out of the heatstink tubing that should have provided some strain relief, having broken at the solder joint to the resistor.

A quick & easy fix, after which I reapplied even more tape to hold everything in place.

Maybe it’ll last two years this time around …

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Photo Lamp Mount: Moah Plastic!

One of the cold shoe mounts I made for the photo lamps cracked:

Photo Lamp Mount - fractured
Photo Lamp Mount – fractured

It’s done in PETG with my more-or-less standard two perimeter threads and 15% 3D honeycomb infill, which is Good Enough™ for most of my parts. In this case, there’s obviously not nearly enough plastic in there!

Redoing it with three perimeters and 50% infill should improve the situation, even though it looks identical on the outside:

Photo Lamp Mount - reinstalled
Photo Lamp Mount – reinstalled

I didn’t replace the other mount. If it breaks, it’ll get the same 50% infill as this one. If this one breaks, I’ll try 75%.

An easy fix!

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Huion H610Pro (V2) Tablet vs. xsetwacom

For unknown reasons, likely having to do with ordinary system updates, both the Huion H610Pro (V2) tablet’s device name and the display output’s name have changed. This came to light when I discovered the tablet’s stylus was no longer constrained to the landscape display, which worked fine when I set it up barely a month ago.

Running the setup command manually:

xsetwacom --verbose set "HUION Huion Tablet Pen stylus" MapToOutput "DP-1"
... Display is '(null)'.
... 'set' requested for 'HUION Huion Tablet Pen stylus'.
 <<< snippage >>>
... Checking device 'HUION Huion Tablet stylus' (11).
... Checking device 'HUION Huion Tablet eraser' (19).
Cannot find device 'HUION Huion Tablet Pen stylus'.

Apparently, the device formerly known as HUION Huion Tablet Pen stylus is now called HUION Huion Tablet stylus.

Fine, I can live with that. Try again:

xsetwacom --verbose set "HUION Huion Tablet stylus" MapToOutput "DP-1"
... Display is '(null)'.
... 'set' requested for 'HUION Huion Tablet stylus'.
 <<< snippage >>>
... Checking device 'HUION Huion Tablet stylus' (11).
... Checking device 'HUION Huion Tablet eraser' (19).
... Device 'HUION Huion Tablet stylus' (11) found.
... Found output 'VGA-1' (disconnnected)
... Found output 'DP-1' (disconnnected)
... Found output 'HDMI-1' (disconnnected)
... Found output 'DP-2' (connected)
... CRTC (2560x0) 1440x2560
... Found output 'HDMI-2' (disconnnected)
... Found output 'DP-1-8' (connected)
... CRTC (0x0) 2560x1440
... Found output 'DP-1-1' (disconnnected)
Unable to find output 'DP-1'. Output may not be connected.

Apparently, the video output formerly known as DP-1 has fissioned into DP-1-1 and DP-1-8, with only the latter connected. Weirdly, nothing happened to DP-2.

Once more, into the bleach:

xsetwacom --verbose set "HUION Huion Tablet stylus" MapToOutput "DP-1-8"
... Display is '(null)'.
... 'set' requested for 'HUION Huion Tablet stylus'.
 <<< snippage >>>
... Checking device 'HUION Huion Tablet stylus' (11).
... Checking device 'HUION Huion Tablet eraser' (19).
... Device 'HUION Huion Tablet stylus' (11) found.
... Found output 'VGA-1' (disconnnected)
... Found output 'DP-1' (disconnnected)
... Found output 'HDMI-1' (disconnnected)
... Found output 'DP-2' (connected)
... CRTC (2560x0) 1440x2560
... Found output 'HDMI-2' (disconnnected)
... Found output 'DP-1-8' (connected)
... CRTC (0x0) 2560x1440
... Setting CRTC DP-1-8
... Remapping to output area 2560x1440 @ 0,0.
... Transformation matrix:
... 	[ 0.640000 0.000000 0.000000 ]
... 	[ 0.000000 0.562500 0.000000 ]
... 	[ 0.000000 0.000000 1.000000 ]

Well, that worked.

Actually, I had to constrain the stylus to DP-2, then jam it back on DP-1-8, to spread the tablet’s horizontal extent over the entire monitor. Updating the startup script started the tablet properly the next morning.

The new device name certainly makes more sense and, perhaps, the X output connection now recognizes the landscape monitor’s ability to pass its DisplayPort video stream along to a second monitor.

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Blackburn Flea Bike Headlight

A Blackburn Flea bike headlight and its USB charger emerged from the packs on our Young Engineer’s Tour Easy, but the battery was completely defunct. With nothing to lose, I applied a small screwdriver to crack the case:

Blackburn Flea - opening case
Blackburn Flea – opening case

The battery is a single cylindrical lithium cell:

Blackburn Flea - battery
Blackburn Flea – battery

The USB charger seemed defunct, as it produced only a few dozen millivolts when connected and plugged into its wall wart. Cracking its case revealed a tiny buck power supply with no obvious damage, but also no output.

So I manually charged the cell:

Blackburn Flea - external recharge
Blackburn Flea – external recharge

Definitely not recommended practice, but a bench supply set to 4.1 V and current-limited to 100 mA gets the job done: the current stays at 100 mA while the voltage rises to 4.1 V, then the current drops to just about zero over the next few hours with cell held at 4.1 V.

Unfortunately, the cell really was defunct, even after a few cycles, so I conjured a not-dead-yet lithium cell from the heap:

Blackburn Flea - measurement setup
Blackburn Flea – measurement setup

Given a good supply, the Flea still works perfectly:

Blackburn Headlight - Kyocera Li-ion - 50 mA-div
Blackburn Headlight – Kyocera Li-ion – 50 mA-div

The yellow trace shows the battery holding at 4 V while the LED current runs at 150 mA (3 div × 50 mA/div). You wouldn’t want to run ordinary 5 mm LEDs at nearly 40 mA, but Blackburn surely specified good parts.

Replacing the Flea’s internal cell seems impossible, given its peculiar form factor, and grafting the PCB to an external cell makes no sense, given that it’d then need a custom bike mount.

So another chunk of electronics goes in the e-waste box.

Ride on!

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Needle Case Repair

A needle case emerged from the bottom of a drawer in need of repair:

Needle Case - unglued
Needle Case – unglued

The original joint used solvent glue and I suppose I could refresh it with acetone, but two blobs of hot melt glue seemed easier and, IMO, more durable.

In any event, it’s once more ready for use:

Needle Case - repaired
Needle Case – repaired

Hooray for another zero-dollar repair, although you can see why nobody else does them these days.

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HP 7475A Plotter: Ceramic Pen Tip Wear

An upcoming show-n-tell prompted me to make sure the HP 7475A plotter still worked and verify the pen stash. One of the ceramic pens expired during the first test plot and a refill didn’t improve its disposition, so I pulled a new-old-stock pen from its wrapper.

As expected, the defunct pen’s ink supply core had worn down to the surrounding ceramic nib:

HP 7475A Ceramic-tip pen - worn core
HP 7475A Ceramic-tip pen – worn core

The new pen looks like it has a brush sticking out:

HP 7475A Ceramic-tip pen - fresh core
HP 7475A Ceramic-tip pen – fresh core

The new pen’s core looks slightly larger and, in fact, it’s labeled as 0.4 mm rather than 0.3 mm. The new-old-stock pen stash includes a few 0.2 mm ceramic pens; I should think of something requiring hairline detail.

It passed the manual scribble test and promptly ran out of ink during its first plot. I injected some blue ink and it’s now plotting happily for the first time in its life.

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