Archive for the ‘Uncategorized’ Category

Eurocom laptop backlight repair (bypass?)

February 20, 2019

So, there was a small issue with my laptop.  It was dirty.  I cleaned the screen with glass cleaner and wasn’t too careful about where the liquid got.  Later that night the screen fizzles out.  In summary The not-water part of the cleaner corroded on the LCD connector on the display and no matter how much I cleaned it I couldn’t get it all functional.  I ordered a replacement panel (LTN156FL02-101) and a replacement cable (6-43-P7501-022-1C) from ebay and aliexpress respectively.  The panel came in first and I was excited to install it, in that excitement I tried seating the old laptop cable on the new (used) panel a couple of times and eventually I stopped getting backlight and smelled electronics burning (oops).

eurocom backlight circuit

Luckily this is a Eurocom, which means it’s a rebranded Clevo, which means I can get the schematics for it.  I have the schematics for the P775DM2(-G) and mine is a P751DM2-G and this section is the same between them.  Above is the chip that I found charred and destroyed.  The MTS3572G6 was burnt to a crisp.  I tried to order one but ebay had none, digikey had none, aliexpress had none, it seems to be a very specialized part (N-channel P-channel pair, like a darlington).  I could have gotten some similar FETs and bodged them back in, but after reviewing the circuit it seems that all this does is turn on the backlight.  Before I did this I had no idea if this would mean that it would always have the backlight on when the lid was closed, or other un-intended consequences.  But I also saw this:

edp circuit.PNG

This shows that the panel handles the brightness on its own, and even has a backlight-on line, the part of the circuit that fried seems to let the video card turn off the power to the backlight to save power (I’m guessing).  Based on all this bridging PJ45 would seem to fix my issue.  But if it happens again I’ll break something upstream and I don’t want that.  I could install a fuse at the jumper, but what reating? The burnt chip is good for… 20A? That won’t do (and I don’t believe it).  What are the ratings on the panel then.


Looks like 900mA.  I picked the next up size polyfuse (1100mA) and got to soldering.  It’s not pretty.


That connector at the bottom is the graphics card socket, this all had to fit under the graphics card.  After re-assembling this thing for the tenth time in a week it boots up!  The new screen has a stuck pixel but that’s what I get for buying used instead of new.  The un-intended consequence is that I now have screen on boot every time.  Previously, when not in UEFI mode the screen would not light up if the laptop had been on recently (20 minutes or so).  I never found the root cause of this, but once windows 7 booted and the driver asserted the graphics card everything was fine.  Now it seems the display is always on for boot.  Don’t ask me why it used to have a cooldown time, I tried everything including removing the bios battery and resetting to factory defaults.  This jumper happened to fix all the problems I had with this laptop.


Printer motor controller reverse-engineer (ish)

February 20, 2019

How it came out of my junk box

Back in college we salvaged and gutted an old roll around printer.  Inside were like a million magnetic clutches, a bunch of rods, belts, and gears, and some of these motors.  The motor is self contained with its own control board and the silkscreen is labeled but the chip returns no results when googled.  Here is how to make it move:


That blue capacitor was a guess at the value, it’s on the 24v line and the original fell off years ago


HL – High/Low? needs to be 5V

Lock – magnetic clutch? dunno, but it’s getting the complement of the clock signal

Clock – speed input speed control, 5v square wave (10-600hz)

S/S – start/stop? dunno, bogs down when pulled up or down, seems to speed up a bit when tied to clock

GND – logic ground

+5V – logic supply

G24 – motor ground

+24V – motor supply

The chip is labeled: HFENGINE / VG30DSP / 4CA8G and I had no luck locating it with google.  This is a functional implementation, but probably not optimal.  It was a crapshoot even trying the complement of the clock signal on some of the lines and it seems to be stable.



Scanning Electron Microscope repair – CA3098E replacement

February 2, 2019

So, a buddy of mine just picked up an Amray SEM.  I have no idea what model, but apparently there’s a mailing list community of hobbyist and they’ve never heard of this particular model.  That’s a good sign.  After trying to set it up several problems were found and fixed (I’ve got to start documenting things again) we came across this poser.  There are four thermocouple inputs on the board, amplified with some opamps, and that signal is piped to a single display (galvanometer) via some analog switches.  None of that interfaces with the microprocessor, except for the fact that all four analog signals (post amplification) run into four of these CA3098E hardware hysteresis chips.  Simulating a signal for the thermocouple using a 10 turn potentiometer and a AA battery we found that the hysteresis chips were not doing what they should.  The datasheet is pretty clear that there’s a high and low setpoint, and input and an output, and the output was not changing when the input went above or below the setpoints.  We really didn’t have a way to tell what else it should be doing so we declared them bad.

With no source for these chips other than some from e-bay which were probably salvage anyway we resolved to build a replacement.  The first thing that came to mind is using a literal textbook as reference to build the textbook op-amp hysteresis circuit.  There was a problem with this approach: despite thinking we came up with the right equations it did not simulate right in LTspice.  In the end it ended up that comparators are different than opamps in ways this circuit cares about, but it only took like three hours to figure that out.  The problem I had with that circuit was that it only used one setpoint and some carefully calculated resistor values, I’d rather it be a real drop-in replacement for the original chip and take the two setpoints that the board has trimpots for so it could take the original chips if we come across ones we want to use.


Matt’s circuit, smaller but requires a different setpoint and if you want to change it you have to recalculate those resistors

My circuit is an example of brute force in electrical engineering.  No calculations, no carefully picked resistor values, just building blocks.  Problem statement: we take one input and two setpoints, switch the output high when the input goes over the first setpoint and the output only goes low when it goes below the second setpoint.  The output of the entire circuit is open collector and can be pulled up to whatever the output wants, which is useful for someone working with chips that are basically only good to 5v.  To me this sounds a lot like an SR latch, you set the output high with one pin and reset it (set it low) with the other.  You can build this latch out of NOR gates, I used NAND because we have buckets of 7400 chips I wanted to use up.  To drive the 7400 chip I needed a 5v rail derived from the 15v that drives the chip.  Rather than using a linear regulator which would burn a lot of that as heat I opted for an off the shelf buck converter hardwired as a 5v output (the practical upside of which is that there is now a usb port inside the machine if you need it for anything).  The comparators that drive the input of those are an LM339 (good to 15v) and I used three out of the four in the overall design.  The output of the latch is used to drive that third comparator which is compared against a resistor divider making half of the 7400’s power rail so it simply follows the output.  This buffer is to give the output of the circuit an open collector output as the 339 is just that (I’ll have to remember that trick when interfacing with different voltage systems).


My circuit, bulky but perfectly replicates the subset of this chip that we actually use

The final design goes like this:

Input goes to one input on comparator A and one input on comparator B

setpoint A goes to the other input on comparator A

setpoint B goes to the other input on comparator B

15v drives the comparator and the buck converter to generate the 5v rail

comparator A and B are the inputs to the 7400 SR latch (pulled up to 5v since they are open collector)

5v rail is used to drive the 7400 and generate the 2.5v reference voltage

one of the outputs of the SR latch goes to comparator C

the 2.5v reference voltage goes to the other input of comparator C

the output of comparator C is the output of the circuit (pull up to the right voltage is on the PCB we’re interfacing to

This circuit is a real challenge because you can flip the polarity at basically any point, and I have purposely left out any mention of which is correct because I don’t remember what I did but at one point it was wrong and at another point I fixed it somehow.  You also have another two NAND gates to use which can be used as NOT gates if you don’t want to swap the inputs on a comparator you wired wrong.  This is an interesting project for using analog and digital components as well as interfacing to an existing circuit without using any programmable parts.


Yeah, my fix is kinda like this

AMC Eagle automotive breakers

June 23, 2017


Original diagram of inexact provenance

While replacing the dome light bulbs with LEDs (that post will be up when I’ve figured out what I broke to make them stay on all the time) I blew the dome light fuse, and I didn’t have another one.

original fuses (and my electronic flasher with polarity swapped)

Rather than buy a fuse I checked and found that for most higher values of automotive fuse there are breakers available.  These breakers take more to blow them than the original fuses, I know this because I blew the dome light one intentionally so I wouldn’t run down the battery and it takes more than a tap with a screwdriver to make them pop.  Despite the danger of having something less sensitive as part of my ‘please don’t go up in a ball of fire’ safety system I decided to go with breakers for convenience.


Our Eagles use standard (not mini, maxi, or micro) automotive fuses and values of 3, 7.5, 10, 15, 20, and 25 amps.  The 30A one is already a breaker in mine and I don’t have power windows so I can’t report on that one.

Living in the future

I replaced my 3A fuse with a 5A breaker, my reasoning is that usually there is not a low resistance path that causes heat build up that will hurt the vehicle.  Usually there is a dead short that if left alone to pass 50 amps or so will burn up the wiring quickly.  This breaker will still protect against that, but I admit I am opening myself up to potential problems on the lighting circuit.  If I ever find a 3A breaker I’ll install it.

The home page for this project is here, it has a link to the album of pictures.

Don’t throw that away: how to stay sharp and be productive

May 31, 2016

This marks the straw that broke the camel’s back.  This marks one too many times that I’ve heard sweeping statements of opinion masquerading as fact.  The last time I point out how my point of view contradicts someone else’s and I’m dismissed as an ‘exception’ when I have exactly as much experience and data to argue my point.  This is quite an over-reaction to a recent Hackaday post but as I get maybe 50 visits a day and am not trying to build readership I really don’t care.

Now, similarly to the article that sparked this, well, it feels like it’s going to be a rant.  I will preface this by saying that for some people having only a couple of things sitting around with which you can build things may be fine.  If you’re the sort of person whose creativity and desire to build stuff can wait until amazon or, god forbid, china post can deliver you the parts to build your latest creation then this article is not for you.  This article is for those of us who get struck with inspiration to make something and will make do with whatever’s around just to see it work that night, or weekend, or month (god damn you china post).

<afterthought:  This post uses the word ‘I’ a lot, and that’s because there is one point of view from which I can speak, my own.  I won’t pretend otherwise.>

It’s taken me a long time to reap the fruits of my hoarding.  When I started out I was saving BIOS chips off motherboards and broken VCR heads.  Over time what was useful and what was not became apparent and I threw out all the stuff that was not useful.  You may think I’m stepping on my premise very early on, but let me define what I mean.  I am not advocating for keeping trash around.  You may use a gum wrapper in a clever hack now and again, but that’s no reason to save them all.  I’ll get to my reasoning in a bit, but first: some concrete examples.

One particular point where I found that what I had collected wasn’t worth keeping was when I opened up a box of old salvage and finally realized what that old VCR head was.  I had saved one going very far back which meant it had a fiberglass PCB on the bottom, and careful examination showed it to be a fairly nice slip ring bearing.  I could use this to pass several signals through a rotating shaft.  This is a cool find indeed, but the younger version of me (not knowing exactly how I might use it) had broken the PCB in just the wrong place which made it useless even with my improved skill level.  I do not have pictures of this example of waste that I held on to but eventually threw out, but thinking back I’m willing to bet I could have made use of it today since my soldering skills have vastly improved since then.  This is an example of how I decided to save something that I wasn’t sure how I could use, I then realized it was garbage, and I’m now thinking that if I’d held on to it a little longer it could have made some project a whole lot easier.

As I age (I assume most of you do as well) I find my skills increasing with electronics design, assembly, and reverse engineering.  This means that the newer and older eras of technology that I’ve salvaged become more useful to me as I grow more experienced.  There was a time where I would cut the controller chip off a VCR VFD and wire up to all the pins individually.  I’d then put it in a box for when I felt like figuring out how to make a driver for it.  Now I tend to research the driver chips and only break the circuit where the least amount of modification is necessary to make the circuit do what I want.   These are both valid methods of using some unique technology, I just favor the one which takes more research and less work these days.  This may be because of a revolution in information availability that has come about in my lifetime.

At age 10 I had no use for old motherboard bios chips, but over the years I’ve found out how parallel addressing works, bank switching, and tons of other cool stuff.  I happen to have a UV lamp that I can use to erase some of the older chips (thank you electronics goldmine surprise box) and a programmer that can do almost anything.  That, coupled with the fact that atari 2600 cartridges were basically just an eeprom on a board made it very easy to burn custom roms (several per rom with some dip switches even).  When it’s 10pm and you’d like to burn an atari rom for an event the next day there isn’t exactly time to wait for digikey to ship you the exact part you need, and you come away more educated if you have to figure out how things work rather than just putting together a kit.

When you create a workspace there have to be specific goals in mind.  What is the need that it serves? Is it to be able to make 50 wiring harnesses in a week for a new client’s prototype, or could you be asked to whip up one really unique device.  Is a large stock of a small number of components critical to your daily activities, or will one of each do until you get around to scrounging/ordering more?  If you’re the person to whom standards are important then by all means buy 10 5v power supplies and have them waiting for a use.  I’ll have my assortment of various things and if I need more or less I’ll use a dc-dc to go up, or a zener/linear regulator to go down a tad.  If I need AC I know for most of my power supplies I can just crack them open and take of the rectifier, they’re not the most efficient, but they are versatile with a little know-how.

I’m advocating for keeping all sorts of odd stuff, but that’s not to say it shouldn’t be sorted.  Sorting is one of the most important things I’ve gotten good at.  My method includes lots of fishing tackle boxes full of cr2032 holders, piezo speakers, trrrrrrrrrs jacks and plugs, reed switches, ferite cores, d-sub connectors, buttons, switches, antennas, light bulbs, and other errata that has been collected over the years.  I don’t have a ton of each thing, but they all seemed useful at one point in time and by now I’ve accumulated enough knowledge to be able to use just about all of it if the need arises.  There’s a bin full of fuses.  I seldom have exactly the right size or shape, but if I want a modicum of protection in a new hack I’ll throw one in-line to see if I’m in the right order of magnitude.  Most of the things I have accumulated and then thrown out I didn’t know what I would use it for originally, but once I learned a bit more it became apparent that it wouldn’t help me much in the middle of the night hacking sessions.

The method I use for storing/pitching things:

  • Do I know what I would/could use it for right now?
  • How soon may I want to use it?
  • If I get rid of it, how easy will it be to get back? How fast can I find another?
  • What will I do with the space it frees up?
  • How soon do I want the use of the space it takes up?
  • How hard is it to get rid of?

Let’s take a couple of examples:

Tektronix 555, salvaged from my college, needs lots of work but all there and in beautiful condition.

  • Do I know what I would/could use it for right now?
    • re-cap, try to restore to working, not all that useful but very cool
  • How soon may I want to use it?
    • it’s been years, I’ve lost interest, not very soon
  • If I get rid of it, how easy will it be to get back? How fast can I find another?
    • not too hard but it is in nice condition, and shipping will be murder even if I find one
  • What will I do with the space it frees up?
    • not much, put up a better workbench in the garage
  • How soon do I want the use of the space it takes up?
    • not soon, 3 or 4 projects come before the workbench there
  • How hard is it to get rid of?
    • I don’t want to drive to hamvention or have to meet up with someone from the tektronix rescue list

Conclusion: it can stay for now.

HP 16500B logic analyser, bought from auction for $20 with shit tons of probes and clips and the HP-UX terminal box.  I converted it to CF card for the sake of the hard drive.

  • Do I know what I would/could use it for right now?
    • it’s a bit of a learning curve but a cool tool, who else has a 100 channel 500MHz logic analyser?
  • How soon may I want to use it?
    • eh, I don’t do much work that needs that stuff, the address decoding is only useful for vintage processors
  • If I get rid of it, how easy will it be to get back? How fast can I find another?
    • if I give it to a friend not too hard, if I have to buy another one I won’t get that good of a deal again
  • What will I do with the space it frees up?
    • at the time I was moving, so small footprint was good
  • How soon do I want the use of the space it takes up?
    • moving, so, soon
  • How hard is it to get rid of?
    • I convinced a friend to take it, I just sent it back with him when he visited

Conclusion: let him hold on to it

These stories can go on and on.  Apple ][ GS? given to a fan.  TRS80 COCO2, with box, same thing.  Apple //e (is that how the kids these days do it?) given to friend who thought it was cool.  I usually can’t be bothered to sell things, that takes effort and usually nets a poor profit for my effort.

Moving on to intentionally acquiring things I have no immediate use for.  This is a thing I find essential to building a truly useful arsenal of quality tools/possessions.  When I bought a house I picked up all the essentials I needed as I found I was missing them.  I got brooms, chairs, cutlery, plates, kitchenware, toiletries, but eventually I stopped buying things at my local target or meijer.  Once I had the essentials, then I could focus on the things I didn’t need in everyday life, but that I would want eventually.  Let’s start with a vacuum cleaner (already had a shop-vac), toaster, and stand mixer.  These things aren’t essential so I could spend the time picking out quality, or just cool things that I wanted to own rather than something I was forced into based on need.

Vacuum cleaner.  I already had a shop-vac so this wasn’t a super-pressing need but I knew I would want one eventually.  After my initial research I came up with four possibilities:

  • A Kirby, big heavy, indestructible, and featured in ‘Brave Little Toaster’
  • The Compact C-8 or similar, featured in ‘Gattaca’ and made of a very strong/light alloy
  • A Hoover Constellation, a canister vac that is also a hovercraft for hard floors
  • Central Vacuum system, seems cool and another box to tick on amenities the house has

I decided on the hoover since no one I knew had ever heard of it and it was a concept I liked for my house being full of hardwood floors.  I picked one up for $25 from craigslist and got another attachment at an estate sale for $2.  The one I have doesn’t hover but the repairs needed to fix that don’t seem major.  Even if they end up being insurmountable I will have learned a lot about how they work and that’s half the fun.

My toaster I didn’t spend as much time on, but some research brought me to the Sunbeam T-9.  It has a cool art deco feel, looks a lot like the origin of the toaster in Fallout 4, and reminds me of the Brave Little Toaster.  Mine I got off e-bay for about $45, I know it has the original cord because it’s fabric and paper insulated which was fun when I put a new end on it.  After cleaning it with Quick Glo as recommended on Jay Leno’s Garage (also a product around forever, so it’s probably effective) the shine is a mirror finish.

These are things that I did not need immediately, but would certainly want eventually.  This goes the same for me and tools.  I pick up screwdrivers, hammers, chisels, saws, and basically anything I think I’ll end up buying anyway.  When I get the stuff it’s usually at an estate sale or auction.  I choose to buy older stuff because I know that those products didn’t just fall apart a year after they were bought, they’re several times older than me and will likely keep on being useful after I’m gone.  It’s not just the cost of estate sale tools (which can be quite a steal) but the quality.  If you get an old american forged wrench it will likely last you a lot longer than a modern Chinese cast one.  This even applies for tools with a lifetime warranty.  Do you want to be driving down to Sears every month because the plastic handle cracked off your pliers, or do you want it to just keep working?

I will admit to picking up some tools that I ended up not having a use for.  I got into yankee screwdrivers and basically never got out again.  I love them, the ease of use, the speed without power tools.  I have a friend that picked up a new set but considering I paid a quarter for mine and $7.50 for the bit adapter I don’t regret forgoing the whole modern set and blow-molded plastic case.  I’ve even got one without the spring in it for more precision work.  The ones I regret getting were at an antique mall and had a broken latch.  That means they can not be reeled in and stored easily.  These are basically useless to me considering I already have two good ones.  I recently had a friend ask to look at the mechanism with the intent to copy it, I just offered him some of my scrap ones to cut up.  Eventually, if you have enough patience and space someone will be able to make use of the interesting stuff you’ve collected.

Now, what about when the idea strikes you, and you have to order something? as I remember hearing on the radio (Splendid table, about buying a Tagine), if you’re going to buy one, buy two (or from ‘Contact’ “why build one when you can build two for twice the price”).  The reasoning I heard on the radio was that since there’s an equally small number of things you can do with either of the two major sizes you can get, you might as well get both since you’re apparently serious about using them.  My mentality is similar but has to do with our wonderful global economy.  Example: I want to build a raspberry pi into an amazon echo to try out the echo in my home automation setup.  Problem: the pi has no native analog audio in.  Solution: an $0.89 or best offer usb sound card that takes a month to get here.  I know other people with raspberry pis.  I have multiple raspberry pis.  I would rather spend $0.89 now on one I may never use than wait another month for a second one to come in (even though I can get one locally for $10).  I bought 5.  For that amount of money it was worth it to me to have them in case inspiration struck in the middle of the night (or in the middle of the fracking Chinese new year).  I found someone’s project that used mqtt that they ran on a cheap little router that I could never source locally.  I bought 2  3 (they just came in, apparently I ordered 3) because they are that cheap.  When I bought my little esp boards I got 12 because I didn’t know the supply chain and didn’t trust that they would stay that cheap (I was right, they used to be $2.40).  This all plays into my ‘how easy is it to get another one’ mantra.  I have so many unfinished projects that if I can buy something that will help me finish it then I usually will.

Speaking of unfinished projects, I love those.  I have so many things that I have started but never finished either due to lack of time, skill, interest, resources… I can pick up any one of them and have something interesting to do for a day or two.  If I hit a roadblock I just write down what stopped me, commit and push to github, and pick up another thing.  One thing that is very serious to me is a project that was started in high school.  Imagine a mouse with a built in flash drive.  Not very cool, but it could be useful if you were interested in pen-testing, or just wanted to keep your favorite games a secret from your teachers in school.  The implementation is simple: take a usb mouse, a usb hub, and a usb flash drive.  Strip the hub of all the ports, flash drive too.  Solder wires from drive to hub.  Solder hub in-line with mouse cord.  Cram into mouse.  Done.  Simple? It took me at least 4 years to figure out what we did wrong with that one.  When I cam across that failed project in college it just made me mad how a simple hack could have stumped me.  Looking over it I instantly saw the problem.  I traced the wired for data, and power just fine. The ground had used the SHIELD OF THE USB PORTS as a jumper to get around the board.  Without the ports installed the circuit was open.  Closed the circuit and it all worked.  I will admit it felt like a silly mistake, but that happens on all sorts of scales.  If I can’t figure out a problem, just box it up and wait until I get smarter.  It’s a hobby, I can go at whatever pace I like.

Sometimes it feels like both sides of the same coin.  I want to standardize on one processor so my code is portable, but I have differing needs so I may as well use different parts.   I try to use up the oldest things first, not the unique things that exist as curiosities, but the things losing support.  Use that atmega168, that atmega1280.  Try to find an OS that can make use of that beagle board, panda board, beagle board XM, beagle bone white before no modern image can easily run on it.  Use the things that will get harder to use later.  Make a project that’s easy to finish and stick them in it, glue them down, and forget about them.  Got an old arduino duemilanove? Make a DMX spoofer with it (needs the old FTDI chip).  The possibilities are literally endless, and using a board for something well below what it was designed for helps with stability.  You don’t have to code efficently if there’s twice the ram and flash you will ever use.  Forget shift registers or muxes if you’ve got 60 pins to play with.

I was stymied for so long on lack of money to finish projects, then lack of parts.  I now only lack the interest or skill which only go up as time goes on.  If I find that I need some space to fit new and more interesting things then of course I’ll make way.  If the thing taking up space needs to go, maybe that’s the motivation I need to dive in and finish it,  I have a pile of wood to build shelves, maybe the assortment I have won’t make the most efficient shelves but it will use up some of my spare parts.  When you’ve resigned yourself to not needing something at all then you end up not worrying about it’s use being a waste.  So many of my projects are overbuilt because I had old, robust hardware to start with and in their new job the wear on them will be so little it doesn’t matter that I only had enough parts to build one, that’s all the ones I’ll ever need.

I find myself motivated to finish projects if they’re easy in the aspects that I don’t find interesting and challenging where I like to wallow.  Don’t be afraid to buy parts you might not need, don’t feel bad for holding onto  things you don’t know how to use. Just keep learning and you might thank yourself some day.

Further unearthing of the Hit-Clips technology

June 15, 2014

A few months ago I was reading hackaday, like we all do when I ran across a curious article.  The article was this one from ch00ftech on reverse engineering the Hit-Clips trendy portable audio technology.  I found this odd for several reasons, but mostly because I just assumed everyone knew how they worked.  The reasoning for this assumption comes from having torn one apart as a kid, deemed it trivially simple, and gotten bored with it in minutes.  I remember quite vividly one christmas (or was it a birthday) when my sister got one as a present and condescendingly sneered that it’s useless ‘without a player’.  Oh how wrong she was.


It’s true that you can’t really do anything with just the flash chip sitting there in the palm of your hand, but the player is one of the simplest devices possible.  It consists of a speaker, a battery, and a button.  All the smarts are located in the chip, the ‘player’ is just a breakout for the chip.  I, however have a slightly more interesting piece of retro technology to dissect: a record-able Hit-Clip.

The first thing I would notice is the bright and shiny “Yahoo” logo, this being from the year 2000 those of you that remember the dark times before lord and savior google led us to the light will feel either a wave of nostalgia, or nausea.  This device was marketed so that you could record your own sound clips of uselessly short duration and play them back at your leisure.  Taking a look at the circuit board one might notice that there is no brain in this player/recorder.  There’s hardly any components really, let’s take a closer look.


There we have a speaker, headphone jack, two resistors, a capacitor, battery connections, and a card edge connector.  The card edge connector has six pins, but only two of them are connected to anything.  That connector is the part that makes this particular player unique, that’s the audio input.  There’s no fancy serial connection like the computer connected barbie of the same era, those connections are good old-fashioned analog audio.  Presumably they didn’t use another headphone jack because the demographic for this product could not be expected to read and understand labels like ‘input’ or ‘output’.  I remember (and some checking around will yield the manual) that there is a cradle that this connects to for recording.  The battery connection is pretty obvious (and labeled) so I quickly reversed the schematic and came up with this:

pin labeling is correct, but the schematic omits the play button


I find it nice that they actually used the switched headphone jack on the bottom correctly so as to mute the speaker when headphones are plugged in.  The low-pass filter that was talked about in the more thorough article linked above is simply the mechanics of the speaker, or, on the case of headphones, an in-line resistor.  I would have figured the resistor and capacitor wired together would have been in the audio circuit, but they were just on the power lines as a filter.  The interesting part about this device is the recording functionality, and while I have pictures of the board inside the module I didn’t reverse the schematic, mostly because I am not going to un-pot the chips anyway so it doesn’t interest me enough to do so.  Here it is, the Hit-Clip recorder revealed:


Just because I don’t feel like tracing out that circuit doesn’t mean I’m not interested in seeing it done.  I will drop this in a flat rate envelope to anyone who convinces me they are going to reverse engineer it and do a write-up because it would be nice to get that information out there.

Bleeding wire?

March 22, 2014

We were doing some remodeling at the old hackerspace and cut a wire from an old intercom system that was doing nothing but hang in the way.  A while later we noticed a puddle under it, thought not much of it.  Later there was a bigger puddle and then the jokes got more incredulous.  WTF the building is bleeding?  It’s very thin oil, possibly used for lubing the cable up when it was pulled through the insulation jacket, but that’s a lot of oil for that.  This is unshielded, untwisted audio cable, maybe it’s some sort of shielding or impedence matching?.  We’re a bit stumped out here at i3Detroit, anyone got a clue?

UPDATE: the wire does have some electrical insulation and the conductor are not made of paper.  The colors are red, black, and yellow; the pinout could be anything, but I think it’s probably power, ground, and signal.