Three different variants of Chinese fake ULN2803 chips available on Amazon and eBay. No genuine chips are available on either.
Bonus: “18 pin” DIP socket from Chinese mega-dumpshit-flooder uxcell, who deserve their very own angry shitpost. Hey at least they didn’t send me mis-molded automotive trim clips instead of LED mounting bezels OH WAIT THEY DID
I’ve used up all my actually genuine ULN2803s so I don’t have one for comparison, sorry. 🙁
(We’re saved! The original Epson ERC-09B ribbons appear to be available again via Amazon.)
This post has been technically deemed a shitpost because WD-40 is involved. Also something that looks like Comic Sans.
This is the tiny printer ribbon used on the TFT EAS 911 and many other devices using a small dot matrix printer mechanism. This particular unit is hilarious, it’s less than half an inch thick and appears to contain a one pixel printhead!! The way it works, noisily, is that the printhead cycles back and forth on a bihelical gear as the paper feeds one pixel height at a time. It takes like a minute and a half for the log output from a RWT (Required Weekly Test) to creep noisily out of there.
So the ribbon was fading away on this one and i opened a fresh… new… old stock (uh oh) box of ribbons. They were all dried up in the box.
The ribbon feed knob wouldn’t move the cloth ribbon at all. Curious, I carefully pried the top off.
Larger ribbons as used in some dot matrix printers like the Citizen 200GX/GSX140 models had a big boxy space filled with lots of ribbon that kinda folded up in there and flowed to the other end. Smaller ribbons that went on the carriage (Okidata, IBM, and Apple printers were like this) usually contained a foam roller that stored ink and transferred it to the ribbon. They were easy to re-ink; I always just applied stamp pad ink and WD-40 with good results. The light mineral oil from the WD-40 helped the ink transfer and lubricated the print head pins.
This just has a small band and two foam rollers. The ink was there but dried, so I just applied WD-40 to the ribbon and both rollers.
I tried this on a second one in the box but it seemed its feed roller had separated – the plastic core spun free in the foam sleeve. That seems to be the game over point on these things, it can’t feed anymore once that happens.
I’m not sure if these are still made fresh somewhere. I’ll have to check later. For now, Fun With Subcarrier Audio is on the agenda.
It’s not uncommon among broadcast equipment that it contains a small off-the-shelf embedded PC, often running Linux.
It’s also not uncommon that the equipment will just up and die one day for no seemingly good reason, however, while the reason is a maddeningly silly one— it’s easy to get it running again!
So here’s the most common one I run into. This is on an SSL (Solid State Logic) NetBridge, which is part of their system that— well, I’ll admit I have no clue what it does.
The problem: After unplugging the box and plugging it back in, it never started up right. A front panel LCD lit up and indicated something weird like it was waiting for connection to the host, but never did anything beyond that point.
Remove about 64 screws aaaaaand…
Believe it or not… nothing too special here. This is an off the shelf VIA Mini-ITX platform motherboard. If you had to, you could track down a replacement entirely. The RAM is just standard RAM, so if it went bad you could swap it. I forget what’s on the other end of that ATA cable but it was probably a CompactFlash card in an adapter.
Now, look under that multiport serial card’s corner. See the coin cell battery standing at attention in the vertical holder? Well, it was more like… a dead parrot nailed to its perch.
You can just see one wire connected to the header for the front panel LEDs and buttons. In this case I think it was on the reset pin. There is nothing on the power switch pins.
The way this box left the factory, it was configured to expect that it would never actually shut down. It was expected that the box would just lose power, and the BIOS settings were set to “resume after power failure”. Worked fine until… the battery died and the settings went byebye.
The fix was simple: Open the box, connect a keyboard and monitor, short the pins on the front panel header for “power button” to wake the board up, enter the BIOS settings and configure them appropriately, then put all 64 screws back in the thing.
I dunno, maybe it wasn’t actually 64, but it was a LOT, man.
I’ve seen the same kind of setup used also with a capacitor across the power button pins as described in this car PC article; a certain type of satellite receiver used in radio stations (I forget the make/model!) and the Comrex Access rackmount units used this as well. I believe on those it was more a backup measure to ensure the box still started if the settings got lost, though.
It probably wouldn’t hurt to keep a spare motherboard around for these units. In some cases the software is very dependent of the hardware being JUST so. In advanced and, frankly, ridiculous cases, the software may have a license key linked to the MAC address of the onboard network card, and you may have to swap a surface mount serial EEPROM. (a pox on your house to anyone who implements this…!!!!)
Also, any easily removable storage device may be backed up for future recovery if needed. My usual solution is to just take an image of the whole drive from a Linux system. You’ll probably have to do these as root.
sudo dd if=/dev/sdx of=backupFile.img to create the file (insert appropriate device node of course)
sudo dd if=backupFile.img of=/dev/sdx to restore it (contents of the device will be overwritten!)
If you use a similar size or larger media as the replacement, it should work fine – I’ve never seen anything care that blocks exist beyond where the partition map says they do.
There are a few substances you should watch out for in the electronics field. No, I’m not talking about lead, not even about beryllium…
Unobtainium. This is a substance only really rumoured to exist, yet it’s often the base material for parts in something you’re working on. Nobody can find it now, but there’s always someone, maybe you, who knew where to find the Unobtainium parts… 25 years ago in a tiny shop that’s long gone and replaced by a check cashing store. Unobtainium is known to exist in all three states of matter, but once it becomes gas, it irretrievably escapes ….
Expensivium. While it can be obtained, its scientific purpose is totally unknown. However, Expensivium is the most maddeningly, frightening thing to find as part of an electronic part, for its presence means that these parts will be subject to wild increases in price whenever you need them. Expensivium is usually added to the composition of semiconductors that have been on the market a few years, rf power transistors, high voltage capacitors, wire and cable.
Chineseium. A very inexpensive but disappointing element, it has often been unsuccessfully used as a substitute for Expensivium and Unobtainium. Parts based on excessive amounts of Chineseium will usually fail very quickly due to this material dissipating right out of existence. Attempts to refill a system with lost Chineseium will not theoretically work, as in the theories on refilling lost Magic Smoke, for the high concentration of Chineseium will just lead to even more rapid failure.
While Unobtainium, Expensivium, and Chineseium are not directly toxic or harmful to persons, their presence is associated with a scientifically vague yet statistically proven link to migraine headaches and anxiety.
Little do you know, until it’s too late, but many electronic systems feature a sort of latent failure mode that can be triggered by a seemingly asymptomatic event happening seconds, minutes, even days prior.
Meet the Fuck You Cracker.
When the Fuck You Cracker detonates, it goes off taking the software, sometimes hardware, but always at least a bit of your hard work with it.
The event that lights its fuse is often very strange and minor. In the case of Ericsson IRD satellite receivers, one detonator is a loss or glitch in the black burst sync input when the receiver’s internal frame sync is enabled.
In the case of these camera robotics, it’s a slow loss of nitrogen gas pressure in the pedestal which led to loss of even lens zoom/focus control minutes before a live show. Seen here: Deco Drive before the magic is applied.
Other examples I can think of:
Internal software fault on a Mazda 6 ECU causing runaway battery charge to 19VDC
Sony XDCAM deck losing sync and trashing closed caption data on line 9 in a recording quietly– it went from Closed Captioning to Clclososeded Cacaptptioioniningng.
Any number of I/O accesses to an NFS filesystem that’s gone offline
The Monroe Systems DASDEC, where a received EAS alert hangs forever in the machine’s “inbox” if it’s received with an out of range valid time, and there’s no way to delete it or let it expire until the valid window comes up again. This is fine unless you put audio of a national EAS test alert into it, as the infamous Bobby Bones show incident did– the DASDEC will always auto relay this, you cannot override or filter it out, thus not only causing the Fuck You Cracker fuse to burn until it’s valid again but possibly also relighting the fuse on any station that monitors yours………
I’m sure you’ve also run into the Fuck You Cracker. Watch out, it’s a sneaky one.
Found this cast off in the garage here. This unit has less storage in it than the hard drive in my laptop nowadays, but boy, was it ever cool for its time, and the way it’s implemented is nothing short of amazing.
At center: The AIT tape drive. To the left, the loading assembly. At right (not visible) is a small motorized access door and LCD user panel.
Each tape has a barcode label, and this scanner flicks on to read it.
The tape cartridges and the library unit support R-MIC (REMOTE Memory In Cassette). 64 kilobytes of metadata are accessible via an RFID interface.
As the library queries these chips, it does a very strange and very slow little dance, rocking the wheel back and forth. I had no idea what it was doing at first. I suppose I could skip this by turning off R-MIC from the front panel. The barcode scanner works almost instantly, like, you know, any other proper modern barcode scanner 😉
Inside the AIT drive. I just thought its little tiny BLDC direct drive reels were kinda awesome.
The CPU board looks very… well, very Sony… all of THOSE capacitors… Also, the RAM and Flash were put up on that pluggable daughterboard, probably due to this same CPU board being used in a couple different units with different storage needs…
The motor and gear train that move the loader back and forth…
And the big motor that rotates the turntable. The turntable moves on a set of sealed ball bearing rollers, it’s very slick!
At left and right: IR emitter and detector. These just beam right through each tape slot to determine if a tape is in place.
The loader grasps a tape via the two claws at the front, which land in recesses in the back of the AIT cartridge. This allows it to grab the tape cartridge positively and securely for handling. The small metal finger directly to the left of the R-MIC logo on the cartridge is the write protect sensor; if the cartridge is set to write protect, it’ll fall into the hole opened up by the tab having been moved and the opto interrupter flag at the right side of the blue circuit board will clear the sensor to indicate the cartridge has been marked read only.
Load and make ready……….
Video contains loud and very unfitting music. You’re welcome. I want to make a better video of this but my phone is rebooting after about 30 seconds of video… It’s telling me “go buy that BlackMagic Pocket Cinema camera… you know you want it… MICRO FOUR THIRDS GOODNESS…”
So you may have seen me yelling about power line harmonics… here’s what I was looking at earlier this morning. This is the power at a facility I was doing some work at earlier today. The same power has laid waste to two variable frequency drive units and an Omron 24v power supply used to run a Programmable Logic Controller (PLC).
I used the FFT mode on my Tektronix DPO 2012 oscilloscope to better detail what’s going on. The yellow trace is the waveform coming in (you can see it’s not a perfect sine wave). The red trace is a plot of the frequency vs. amplitude after a Fourier transform. This same kind of plot may already be familiar to you: it’s displayed on many audio players and stereo systems as a spectrum analyzer visualization.
If this were perfect clean 60 hz power, I would have only the tall peak at the left which is 60 hz, then it would roll off to the baseline. What I got, however, is this (and a realization I accidentally set my scope’s clock 12 hours off *before* DST kicked in…)
The FOUR other peaks are the harmonics. Initially I thought I was looking at a second, third, fourth, and fifth harmonic, which would put the last one at 300 hz– reading this again though, it’s scaled 500 hz/division so what I’m looking at is the odd order harmonics at up to 540 hz– a NINTH harmonic.
Now let’s look at that third harmonic, the most prominent. That one’s about 20dB down from the fundamental (the scale is 20dB per vertical division). That’s a voltage ratio of 0.1… so the third harmonic, if you were to isolate it, would be 12 volts at 180 hz. That just plain doesn’t belong!!!
A textbook square wave is the fundamental frequency plus all of its odd-order harmonics– 3, 5, 7, 9…. I suppose this makes sense, as if you smashed this AC waveform very very badly you would get a square wave.
Power line harmonics are an annoying effect of loads with a poor power factor. Want an example of a load with a poor power factor? You’re looking at it. The wall chargers for smartphones, power supplies for computers, and even LED, florescent, and compact florescent light bulbs are guilty due to the nature of their power supplies. Without getting too much into the theory I’ll say this: the way they work is that they draw power right at the peaks of the usual sine wave power. This is why the peaks in the above screenshot are getting smashed: that’s when EVERYTHING draws its juice.
Some *nicer* devices incorporate power factor correction circuitry to mitigate this. This usually takes the form of a low pass filter that acts on the amount of current drawn by the device, in an effort to keep it from just suddenly grabbing only the peak. Note that I say— “some”—
The harmonics tend to overstress everything by causing high currents to flow in wires, transformers, power supplies, etc– they are not only harsh to the equipment but they are a waste of energy.
And here, boy, do we ever have ’em.
The solution, ultimately, will probably be to have the local power company install a bank of capacitors for power factor correction on their poles.
Then, hopefully, the power will stop being quite so…….. hungry for electronic snacks……