The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Repairs

If it used to work, it can work again

Windows XP Restoration
Although Thanksgiving is Update Your Parents’ Browser Day, I ended up rebuilding their old Dell Dimension 2350 PC over their New Year visit: it had succumbed to a nasty case of bit rot. It may have had the odd malware infestation, although booting with the invaluable System Rescue CD and unleashing a ClamAV scan didn’t turn up anything exciting.

I had full partition backups from August 2010, so I set up a new hard drive (well, an old drive from my heap, but new to them) with the restored partitions before they arrived, swapped it into the PC, then attempted to boot the Windows Recovery Console from their Windows CD to restore the MBR. Alas, I didn’t set the Dell Utility partition to type DE, thus throwing off the drive letter sequence, and the subsequent thrashing (including a steel-cage death match with fixboot and chkdsk) wrecked the Windows partition.

Figuring that situation out from a simple NTLDR missing boot message took a while.

But after restoring the partition again and doing the WRC dance, we had a perfectly serviceable Windows XP installation that inhaled a year’s worth of Windows updates in a surprisingly short process that required only a single (!) reboot. I tossed a bunch of obsolete & unused software over the side, emptied the Recycle bin, manually deleted a bunch of files in the various temporary directories, updated Firefox, installed LibreOffice, imported the Outlook Express address book from the rotted drive, did not import the email messages, and away they drove.

I had suggested it was time for a new PC, but … maybe next time.

Notes:
- My USB-to-SATA adapter cable injected occasional read errors (which partimage caught), but a klunky drop-in-the-slot vertical desktop adapter worked OK.
- A CHKDSK fixed one or more files message doesn’t really prepare you for the discovery that it obliterated the entire directory structure and left a vacant drive behind.
- The PC had 512 MB of DDR RAM in two 256 MB sticks. I swapped in a 512 MB stick (harvested from an old PC on its way to the recycler) and, as you’d expect, 768 MB of RAM dramatically improved the poor thing’s attitude.
- System Rescue CD is invaluable for this sort of thing.
- What is it with Firefox being stuck at V3 forever, then ratcheting instantly to V9? Version envy?
2012-01-09
Thing-O-Matic: Improved EC Thermistor Connector Orientation
Given that the SMD pads fell off the HBP circuit board and I must replace the connector, I figured I may as well also replace the remarkably stiff MBI thermistor cable with a much more flexible CD-ROM audio cable. Although the EC end of the MBI cable looks like a standard CD-ROM audio connector, it’s been rewired. No problem: this is not an audio application and I’m going to do exactly the same thing.

The Extruder Controller, however, doesn’t have a matching connector and the recommended attachment involves simply jamming the connector onto the pin header, per this detail cropped from that photo in the MBI assembly instructions:

MBI EC HBP Thermistor Connector Alignment – Detail

Here’s a better closeup of my EC, taken from the other side:

MBI Extruder Controller – HBP thermistor connector

The header block breaks out the Arduino’s Analog Input pins, with A6 in the front of that photo. From left to right, the pins under the HBP connector are A6 / +5 V / Gnd. Unfortunately, the connector wiring and alignment puts the thermistor signal on the cable shield, with the Gnd and +5 V wires safely tucked inside. This is, shall we say, suboptimal.

The Gnd connection provides a low-impedance connection to the least-noisy part of the circuit, so putting it on the shield tends to prevent the relatively high-impedance signals within from picking up noise. This isn’t always successful, for a number of reasons, but it’s a Good Idea.

Although probably doesn’t make much difference (it’d just add a bit of noise to the HBP temperature signal), but if I’m going to be rewiring it anyway, the cable shield will be at ground potential with the signal wire inside. Here’s my cable & connector, rearranged to make that so:

EC HBP thermistor connector – revised

The analog audio connector on the back of old-school CD-ROM drives, back before digital audio output from the drives actually worked, had four pins:
- Left (white) and Right (red) audio channels on the outer pair
- Ground (black) on at least one of the central pair
So the red wire will be in the far right-hand socket of the connector shell; depress its locking tab, slide it out of the shell, poke it into the socket between the other two wires, push to click, and you’re set. Conveniently, this puts the +5 V supply on the red wire, which is sorta-kinda standard. Your cable colors may vary; pay attention to the actual wiring and ignore the color code!

Tape the connector in place (with the empty socket now toward the board edge) to prevent the tangle of wires in the Thing-O-Matic’s electronics bay from dislodging it at an inopportune moment:

EC HBP thermistor connector – secured

Admittedly, that arrangement still tucks the +5V wire right next to the signal wire inside the shield, but it’s a step in the right direction.

You could flip the MBI cable around, too, as long as you also rearranged the pins at the HBP end to match.
2012-01-07
Thing-O-Matic: HBP Connector Failure

This has been a long time coming, as the connector shell over that pin connecting the MOSFET to the heater has been getting crispier despite my attention, cleaning, and occasional DeoxIT application.

Burned-out HBP connector

Notice that the burned pin now stands at a slight angle to the others. The PCB pad has no additional copper traces on that side to conduct the heat away from the failing connection, so the joint got hot enough to put the solder into its semi-liquid state, whereupon the springy connector rammed it upwards through the softened plastic shell. If the PCB fab shop used 60-40 lead solder, that’s around 188 °C. Silver solder would reach 220-ish °C. If the solder was eutectic, it would turn liquid and just drip off.

What doesn’t show: the SMD pads that pulled free from the PCB surface, fortunately only under the rightmost three pins leading to the thermistor. Repairing the pads and connector makes no sense, so I think I’ll go with pigtail leads anchored to the plywood, with offboard connectors to reduce the strain on those pads. Powerpoles will be bulky, but maybe pigtails long enough to get them onto the case might work.

As a general rule, soldering wires or connectors to SMD pads with no mechanical support is a Bad Idea and applying repeated mechanical stress to those connectors is a Very Bad Idea. Doing all that on a PCB running well over 100 °C with current right up near the connector’s absolute maximum, well…

2012-01-06
Sony NP-FS11 Batteries: After the Aftermarket
The batteries I rebuilt for our much-beloved Sony DSC-F505V camera back in early 2010 have faded away with constant use. Having already sawed the cases open, rebuilding three of them didn’t pose much of a challenge; this time I added a short tab of Kapton tape to help extract them from the camera socket.

Rebuilt NP-FS11 batteries

Three batteries seems to be about the minimax for ordinary use:
- One in the camera
- One in the carrying case
- One in the charger
You (well, we) can’t keep track of more than three: it always seems one battery gets overused and another gets lost in the dark. We’ll see how three works in practice; there’s a set of six more raw cells lying in wait.

The new batteries produced these results on their first two charge-discharge cycles:

Sony NP-FS11 2011 Packs – First Charges

One battery didn’t come up to speed on the first charge, but after that they’re all pretty close.
2011-12-24
Ativa Cordless Phone Batteries

These were cheap-after-rebate phones with 2/3 AA NiCd cells that lasted nigh onto five years. We rarely talk on the phone and even more rarely use these, so they’re on the dreaded continuous trickle charge and low usage cycle that kills rechargeable batteries. Of course, they’ve been sitting there for five years…

The rebuild was no big deal, although I had to replace the original 360 mAh NiCd cells with 650 mAh NiMH cells (with tabs) because that’s what’s available nowadays. The trickle rate will be even lower relative to the capacity, of course, which may or may not be a Bad Thing.

The packs contained a simple fuse consisting of a thinned section of the usual nickel strap connecting two cells, covered with a fiberglass sleeve under the shrink overwrap. For lack of anything smarter, I harvested the fuse and soldered it in the new pack. although the risk of a catastrophic short seems fairly low:

NiCd pack with thin-wire fuse

The final result looks about as you’d expect, complete with obligatory Kapton tape wrap:

Ativa phone – rebuilt battery

The old pack is kaput and new pack delivers pretty nearly its rated capacity at an arbitrary 550 mA discharge (which is, admittedly, a bit stiff for the old pack):

Ativa phone battery tests

That takes care of one phone… the other one’s probably in the same condition, so I have enough cells to rebuild it, too.

2011-12-23
Roof Shingle Fungus Redux

Cleaned the gutters a while ago and the shingle fungus is getting worse: more sites and more stains. I sprized some general-purpose fungicide on the area over the kitchen:

Shingle fungus – east slope

And down the valley between the north and east slopes:

Shingle fungus – north and east slopes

We’ll see what happens by next spring; I hope the larger moss clumps will take the hint.

However, that short length of copper wire seems to be improving things. Here’s the before:

Copper effect on roof discoloration

Compared with the current state, from a different spot:

Shingle fungus – below Cu wire

The intense streaks have vanished, leaving a uniform lighter gray layer, and the upper area near the wire looks, mmm, less awful than the lower areas. I think running copper wire or zinc strips (which I have not found at the big box stores) along the ridge vent will do wonders, although I’m not sure how to anchor either one along the hip joints between the other slopes.

2011-12-15
Weller EC1201A Soldering Handle Failure
For the last few days, my trust Weller EC1000 soldering iron (well, station) has been misbehaving: shortly after cleaning the tip, it would become covered in charred residue and slag. Today, the LED I’d hacked across the heater terminals inside the base stayed dark, even though the tip was hot, and then became sensitive to the handle position. Obviously there’s a loose wire inside, right?

So I took the handle apart by removing the two screws on the front plate:

Weller EC1201A soldering handle innards

The trick to getting the guts out is to push down on the tab inside the handle that locks the cord strain relief block into the handle. After that, everything comes apart with very little force at all.

Contrary to what I thought, the heater is in the tube surrounding the temperature sensor probe. Looking at the connector on the front of the base unit, the key is on the left side and the wires going clockwise from above the key are:
- Yellow: heater
- White: heater
- Black: sensor
- Red: sensor
- Green: shield
I would have sworn the red & black were the heater, as they have special-looking brass/bronze/copper colored pins & sockets. Wrong again.

The temperature probe comes apart thusly:

Weller EC1201A temperature probe disassembly

Basically, slide the connector and ceramic-coated sensor out of the back of the black shell, then pull the spring-loaded sheath out the front.

I hoped for a laying-on-of-hands fix, but it was not to be: the tip heats while the LED (which I wired there early in the iron’s life) across the heater power remains off. But the LED blinked on intermittently with slight pressure on the iron’s tip; a bit more poking and prodding isolated an intermittent open-circuit to the ground wire just outboard of the strain relief at the handle:

Soldering iron cable failure

A bit more poking & tugging isolated an intermittent high-resistance short (a few hundred ohms, more or less) to a section of cable half a foot from the base connector at the bottom of the cable’s natural loop when the iron’s in the holder.

Unfortunately, fixing all that didn’t restore the iron to life. It seems that the temperature sensor (a thermocouple?) has failed, allowing the tip to heat well beyond any rational temperature. Now that I’m looking, a cleaned solder layer turns blue with oxidation in a matter of seconds and rosin chars instantly. The temperature control knob has no effect whatsoever.

The date codes inside the box show it’s been with me since late 1982, so on a dollars-per-year basis the thing has been a bargain. A new sensor is $60, a new handle is twice that, and I think it’s time for a new iron… at less than the price of the sensor alone, I think that’s OK.
2011-12-14