Scanning Electron Microscope repair – CA3098E replacement

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

TI-58 Calculator battery upgrade

After a weekend at Minicon I came back with plenty of goodies thanks to the trusting nature of Amtrak (look for a CDV-715 post coming up) and one of the smallest was this TI Programmable 58 calculator.

original

I love old bubble display calculators, thermostats, stopwatches, whatever I can get my hands on.

crusty

This repair seemed pretty simple, replace the old Ni-Cd batteries with new ones.  The challenging part was someone already did this once before.

you’ve had some cowboys in here…

The batteries were a snug fit, the power tabs snapped, and I ran out of patience.  The original TI charger for this was rated to put out ~3v although after the bridge rectifier easily identified was somewhere around 6V DC-ish.

looks like a rectifier, that can go

I decided that that’s close enough to 5 for 1977 and injected my new power source there.  My selection was based on what I had lying around which turned out to be a micro-usb lithium charger/boost converter that put out 5 volts and a lithium battery out of an old ipod external battery pack from radioshack long ago (I bought it before the advent of common charger/boost converters for single lithium cells).

all kapton’d up

Put together and with some kapton to hold it in place and a dremel to hollow out the case I successfully added usb rechargability to this old calculator.  I will admit that it is now incompatible with some of the add-ons, but I’m not terribly concerned as I intend to use it just as a pocket calculator.  All pictures (including others not in this post) are here.

useful once again

Drill chuck replacement

For any of you plagued by modern power tools, I have a reminder for you.  Even if you have to get a drill to finish a project right now and your only option is a speed chuck there is still hope.  Just because you had to buy a new tool doesn’t mean you need to be stuck with crap forever, upgrade it! By using a hammer, a large allen key, and some stiff impacts (don’t burn up the motor trying to do this with the drill) you can remove that new crappy chuck and put on a nice old Jacobs chuck with a key.  Gone are the days of skinning your palms when you try to get a drill bit in and out.  Or the instances when you just can’t get enough torque to keep that hole saw from spinning.  With your newly installed chuck and key you have the needed mechanical advantage that makes a drill worth using.  Ever wonder why not even the cheap companies use a keyed chuck on their larger models? That’s right, you can’t get the needed torque.

Wave Bubble Wrong Part

Here’s a quick one.  A long long time ago, in a lab far away… Ok, so some people may know what a Wave Bubble is, some people may not.  Basically, it’s a device that will let you silence cell phones around you.  It may be illegal, but so are all the other good things so if you don’t bother anyone else by doing it you will certainly not have any issues.  The documentation for this device was great, but because of the type of device that means the instructions stayed in a sort of V0.5 state.  This leads to mistakes.  The forums are a help, but with so few people willing to try building it it’s still a bit scattershot.  Parts go out of production, technology moves on, and there isn’t a fundamentally new version of the design available which makes building it even harder.

As part of a group buy of components a friend put together order for boards, parts, and all the needed bits to make this project work.  Well, it didn’t work.  The one major problem I had in building this was that the original BOM we ordered from (I can’t find it, but I trust him) had the AD8403 listed as the digipot.  That was wrong, it should have been the AD8402.  The difference is one digit, 10 pins, and 2 internal digipots.  The nice thing is that the addresses they respond to are the same, and that the smaller ones are just a subset of the bigger ones.  If you are comfortable soldering like me then grab yourself some 80-pin ide cables strip them down, and solder up an adapter.

Now, I can’t say I recommend buying the parts to build this kit.  It’s hard, doesn’t produce something very useful, and if we’re honest you can get one from aliexpress.  If you do try to build one, I recommend doing a bit more research and checking out the wiki.

Microwave oven repair

So, another round of posts to relieve the backlog of ones that I have pictures for.  We had a wonderful microwave at the house I lived at while in college.  It had all the features I could ask for: a temperature probe.  I know some people want power levels, digital interface, or even a rotating tray, but I really really liked the idea of a temperature probe.  I wonder why modern microwaves dropped this fantastic feature.  My instinct says that morons think “I’m not supposed to put metal in the microwave, therefore I can’t use this feature supplied by the manufacturer”.  The ability to put metal in the microwave has been proved as a fantastic way to heat a solder pot or melt pewter for molds (and it is not bad for the microwave).

Now, I mentioned this microwave didn’t have a rotating tray.  That’s not true, it came with an aftermarket one, but no rotation mechanism.  My theory is that the mechanism had an electric motor on it and it turned quite well until someone lost it before we bought it.  I also mentioned it didn’t have a power level selector.  That’s also not true, it had one, past tense.  This time it had one when we bought it and it doesn’t now.  I’m the one who removed it and I don’t feel bad about it.  Originally the switch was sparking and eventually died as seen here:

The fix I originally had for this was a set of switches that replaced this one (I’m NOT trying to source an equivalent to that).  That worked for a while, but eventually we had a problem of complete failure of the power system.  That is shown here:

The method this microwave uses to change power levels is literally by dissipating it through a huge power resistor and switching parts of it in and out of the circuit.  This method is less efficient than modern methods of sending pulses of full power followed by no power to the magnetron, but much more regular and produces a smoother pattern of heating in the microwave.  A nice big 120W wirewound resistor would be the best idea for setting power level, but that’s prohibitively expensive and I’m just too lazy to look.  This microwave got shorted to full power for the remainder of the time it was under my care.  I’m not sure what happened to it, but I’ve only seen one better than it and that one had digital controls, a temperature probe and a rack!

Inside this microwave I found schematics and testing procedures, as it turns out our magnetron is operating within normal parameters of full power.

Schematic

Manual

LCD monitor repair (again)

OK, so this is one of those days that starts with big plans and gets derailed seemingly because those plans were so well thought out.  I come from a group of people that spend their days just repairing things because they’re there.  We have taken it in stride to develop techniques for repairing commonly thrown out items and apply our experience to new items as we get a hold of them, but we rarely document our work or share our knowledge beyond the confines of our lab.  This is the story of what happened when I tried to document what I figured would be a routine repair on a common model LCD monitor.

Our Patient

The monitor (as you can see) is a Dell 1907FPt 19″ widescreen LCD monitor.  The first thing I recommend when you have a device of any kind to repair is to look up that model (or series) and see if anyone else has encountered problems with it.  Hopefully you’ll run across a helpful blog post of someone who took the time to explain the steps they took to debug and fix theirs, so you can cut down on the time it takes to fix yours.  I, of course, didn’t do that.  I have no idea what the common failure modes of this monitor are and what the commonly accepted fixes are, so I blazed my own trail to some hilarious consequences.  Seriously, do as I say, not as I do.  For every blog entry of a moderately successful hack/repair I have there are a dozen failed ones that could usually be avoided by spending some more time researching and less time breaking things.  In the future I hope to post my failures with notes for future pioneers, but my successes are usually still around after the fact so photos are easier to take (since I almost never take them during the event, but months after).

Now, having opened more than my fair share of Dell monitors I thought I’d itemize just what steps are involved.  First you need to remove any visible screws, this usually just consists of the four phillips head bolts on the back (seen above).  Next you need to insert a spudger (yes that’s a technical term, look it up) into the gap between the monitor back and the bezel.  That separation into two pieces is the entirety of the plastic casing on this model.

step one

tabs exposed

keep going, almost there

and there you go, dis-assembled

Once you get the back off of this monitor you will inevitably hear a clatter as something falls to the floor and hides among the junk there until you figure out what exactly was missing so you know what to look for.  What you are looking for is a small plastic button and spring that retains the base to the monitor.  The button is a Dell thing, they have brackets on their stands that allow you to use your monitor with only that stand and not that of another Dell monitor.  These stands are “tool-less” which is slang for “our main consumer base can’t operate a screwdriver”.  The monitor itself has VESA standard mounting holes, but the stands are mostly useful for the monitors with which they came (although I may explore the hacking I have done on these stands in a later post).

The button and spring, free without the back

carefully remove this ribbon cable and the double-stick tape that holds it to the monitor casing

Now we need to just keep removing screws and remember where they came from.  You can usually ditch the shielding if you don’t care about potentially harmful interference as covered in FCC part 15.

remove one cover over the inverter wires

and the other

remove the inverter wires from one side

and the other, while you’re at it remove the screws that hold the monitor to the controller board housing on both sides

the panel without any controller, power supply, or inverter

now remove the screws that hold the heatsink to the casing

screws seen here (note they are flat, they mount flush with the panel

power supply board has had it’s screws removed

mains plug with screws removed

screws in question

Not pictured (I know, with all these pictures I forgot one) is the removal of the logic board’s retaining screws and the mounting hardware for the d-sub connectors (VGA and DVI, although DVI’s not a true d-sub).

controller board

Here is the controller board.  There were no bad caps on it, which is a shame since that would have been an easy fix (unless the problem caused a chip failure).  On the bottom are the ports exposed to the outside.  DVI, VGA, USB-b, and a dual stack USB-a.  This particular monitor has a four port usb hub built in (which I’ll go into later).  The port on the right side of the board is for a two-usb port daughter board for the hub (only passives if anything).  The ribbon port on the right is for the front panel controls (bonus points to those of you who remembered that ribbon from earlier).  It is noteworthy that different versions of Dell UltraSharp monitors use different pinouts for the cable with different numbers of features, but they all seem to use the same size cable and connector so they are interchangeable as far as that goes (buttons have different functions, or no function at all).  The port on the left is for power input (it could be pinned out, but I didn’t as they’re usually labeled).  The top port is the LVDS signals to the LCD panel.

close up on VGA and DVI port electronics.

So, the three chips here are two i2c EEPROMs and one chip that I assume is the receiver for the VGA signal.  The eight SOT-23 packaged devices to the left are probably FETs being driven by the differential signalling on the DVI port (the same as the monolithic analog receiver for the VGA port.  The EEPROMs are of note because they hold the EDID information for each port, they tell the computer that’s connected to the monitor what resolutions are supported.  The noteworthy fact is that these type of EEPROMs are massively useful as they’re easy to reprogram and use in things like PCI network cards, motherboard BIOS chips, and USB peripherals.  The chip with the little white sticker on it is probabbly the i2c EEPROM that holds the settings for the Genesis main controller, setting what the settings on the LVDS panel are.

This is interesting to me because you can now buy generic LVDS driver boards and inverters to make use of that surplus laptop LCD panel and I have this thought that I could re-purpose one of these drivers to be used on a different panel.  This phenomenon changes the standard answer to the question of “I can hook the composite signal of my n64 to this old laptop panel” from “No.” to “Maybe.”.

USB hub

So, this circuit is interesting, it’s a USB hub.  The USB hub is entirely separate from the controller that drives the LCD except for power.  I have in the past had good results tracing out the power for the circuit seen here and cutting power to the rest of the board to use it as a stand-alone hub.  The thing about powered and un-powered hubs is that in most of the hubs I’ve seen is that the 5 volt power is hooked directly to the input 5 volt line on the USB-b port.  The un-populated chip on the upper right side of the board is probably another one of those ubiquitous i2c EEPROMs that would hold the USB Vid:Pid pair (as seen in that older article on the logic analyzer).

Here is the problem, the backlight doesn’t work.  The symptoms are that when you power it on one of the coils fizzes and then the over-current protection kicks in and kills it.  Presumably the coil had shorted, so I did the inadvisable and replaced it with an inexact replacement coil.  That coil fizzed as well, so I figured there was a problem further upstream.  Probably a broken FET that’s passing too much voltage or something, but I never found that out.  My solution was… very hackish.  I replaced the inverter with a new one.  A new one salvaged from an HP film negative scanner lightbox.  I don’t have pictures of that, but the inverter is exactly the came as one out of one of those blue inverter boxes from the mid 00’s that drove the ever classy blue cold cathode tubes (you know, the ones that are really shitty quality and explode periodically).

crazy solution being tested

In this picture I have removed the coil (no more arc-ing (fizzing)) and powered the inverter from the 12 volt out put designed for the amplified speakers that are an optional extra for this and most model Dell monitors.  The problem is that the backlight still shut off after a few seconds.  Time for some more fast-and-loose hacking.

underside of working inverter

So, without tracing out the circuit here I can see a bunch of diodes and resistors tied to the high voltage section of the transformer.  The thing I can assume from here is that a network like that can be used to sense the voltage (through dividers) and waveform (through dividers or zeners) of the output of the step-up transformer.  This type of closed-loop control is advisable so you can shut down parts of the circuit without blowing anything up.  It is also the enemy of simple hacks like this.  Let’s look at the section I modified.

“modified” board

So, of note here is that I removed pretty much everything.  The red stuff is glue used to hold the components down before they were soldered in (or maybe to take the mechanical stress off the solder).  This part of the board was gutted and I assumed I’d have to feed the signal from the other inverter to the sense circuit for this one.  I didn’t.  It just works.  Who would have figured.

you’ve had some cowboys in here…

The final configuration, complete with plastic sheet for insulation and hot glue for adhesion.

It works!

That’s it.  That’s how a simple post on a “standard procedure” repair became a Frankenstein’s monster post.

Replacement power supply build

I say build, it’s more a mod.  A long ,long time ago in a college town far away I helped a friend move into his frat house.  After I did this one of the housemates gave me an old monitor and power supply simply because he didn’t need it.  I gladly accepted it, but when I checked to make sure it was the right power adapter I noted it was a 12v 1a one, the display called for a 16v 3a one.  Now, I don’t know exactly the audience I have (yes I do, it’s web spiders) but I’ll tell you right now: there’s no way that will work.  I mentioned this at the time, but was assured that that was the adapter he always used for it (no it wasn’t).  My persistence at wanting this thing to work may seem misguided, but here’s the thing: this isn’t a computer monitor, it’s a TV.  Now I know what you’re thinking  that’s worse right? Right.  But in this case I don’t want better, I want more.  This TV (Phillips 20pf5120/28) has a cable tuner (useless), a composite input (expected), an s-video input (expected, but appreciated), a component input (cool! my first component input), and a dvi input (what?).  The DVI input can only do a resolution of 640×480 (and only digital), but it’s a 20″ 4×3 LCD TV, what more can you expect?  Let’s look at the specs for a new power adapter, shall we? 16v DC: that’s not too hard, if it were 12 or lower you could use a linear reg on a computer power supply to get that, but it’s not too bad.  3a: here we have a problem; that much current usually warrants the power supply to be inside the device it’s powering so those are a bit hard to come by, or at least they were.  I say that because we are now in the era of scrap laptops.  Yes, that’s right, laptop computers are being thrown out left and right for all manner of faults: broken screen, dead battery, won’t boot, broken power adapter (more on this later).  The thing about laptops is that they take a lot of power, sometimes upwards of 4.5a.  The problem now becomes the voltage.  Laptops generally run off of somewhere between 18.5v and 20v to charge their lithium ion batteries.  Let’s see what the junk drawer has to offer.

image taken post mod

We have a nice 19v 3.25a laptop power supply: perfect! Ok, there’s still that voltage problem; there are two ways to tackle this: a switching regulator, or a linear regulator. The switching regulator is a much more efficient design, but requires parts I did not have on hand.  The linear regulators could not pass enough current (1.5a max) but that’s ok, we’ll just put 2 of them in parallel to get that extra current through.

The design of the linear regulator circuit is simple, we use a fixed voltage linear regulator and a voltage divider made out of two specially chosen resistors to set the voltage to whatever we want.  For this one I just pulled out my phone and used electrodroid, but the calculation is simple to do if you want.  The heatsinks are mandatory since I’m running these regulators at the ragged edge of their tolerances.  There you go, a 16v 3a dc power supply that will give you second degree burns if you handle it wrong.

I swear I build these things better when they aren’t just going to be used by me

Gynecology table repair

I didn’t break this one.  Ok, I just felt like I’d open with that, I don’t get to say that too often.  This also differs from my normal electronics hacking, but I really have this motto: “if someone else can do it, I certainly must be able to” and an addendum: “if no one else can do it, it’s only because they aren’t as good at it as me”.  That’s mostly sarcastic, but it is a bit more honest than “if at first you don’t succeed…”.

This time I’m repairing a gynecology table.  I’ll let that sink in for a minute.  Ok?  Good, let’s move on to the story.  This table was purchased by a very good friend’s uncle for use at his tattoo parlor.  I believe the intended use was/is as a piercing table, and that there was a story that went along with this table that sorta motivated us to get it fixed.  As you can see, this is a vintage table, so repairing it was even more interesting and important.  The problem with it was that when it was moved someone decided to lift it by the tilting part that you see on the right and broke some welds.  I think the original construction method was a series of holes in one sheet of metal, and pegs sticking out of the other so welds could be made along the center of the hinge rather than the edge.

Onto the fix! The easy way to fix this was to drill out the pegs and replace them with nuts and bolts.  Luckily the hinge was bolted onto the seat so all we had to do was unbolt that to take it somewhere else to work on it.  A quick run to Home Depot got us the right parts (and locktite of course), but where could we get a drill? Oh, there’s a metal shop in the basement of a tattoo parlor.  Yup.  Drill press and all.  That was easy.  Some lubricating oil later we had cleanly drilled holes, brought it back and installed it, very easy.

I don’t know what model this was since I’m bad at pictures, but I know that of the things it came with it’s latest patent date is 1943.  So, this has been a tutorial on how to repair a broken post-1943 Hamilton brand gynecology table.  This was the way I spent my last day visiting in Seattle, and it was probably the best way I can think to have spent it.  Full set of pictures here.

LED backlighting a 22″ lcd monitor

This one’s kinda messy, but I was visiting my parents so I only brought my soldering iron and basic tools with me.  I had a friend mention that their lcd monitor was broken, of course the first thing out of my mouth was “I can fix it no problem”.  It was a little more complicated than I thought.  Let’s review the most common failure mode of electronics this decade: bad caps.  What I mean by that is capacitors that have failed, exploded, had their ESR go up, heated up due to that and then exploded, or bulged, or just plain leaked.  The reasons are numerous: there could be an unexpected cooling failure causing the caps to heat beyond their tolerances; there could be too high an ESR as I mentioned; they could even just be, gasp, old! But by far the most common reason for failure is espionage.  It’s a little more mundane than it sounds, there are news articles, wiki entries, and even a website and forum dedicated to it.  I’m just hereto say it has been a godsend for those of us that can open consumer electronics and solder reasonably well.  When you have people throwing out devices worth several hundred dollars each because of a few cents in parts that are fantastically easy to identify and fix… well, let’s just say I know some people who could major in monitor repair and minor in general debugging.

the whole setup, mountain dew and all

This problem monitor happened to be a Sceptre 22″ lcd monitor.  Now, due to the rapidity that people are throwing out monitors I tend to have a large backlog from which I can pull parts (usually entire power or logic boards, sometimes button panels, etc…) but I don’t have any spare dead monitors this big.  Once open (although I should have done this first) it was obvious that the LCD worked, the logic board worked, and the main part of the power supply worked.  I could tell because the only thing that didn’t work was the back-light   This doesn’t preclude it from being bad caps, but it lowers the likelihood   In back-lights I tend to see one of four things go wrong.  First there is the simple bad caps on the inverter input, this wasn’t the case here.  Next there’s the blown PWM chip or blown FET driver, usually SOT-8 or DIP-8, can be blown by heat, time, or voltage fluctuations (sometimes traced to caps). Another potential failure mode I know is shorted transformers; I haven’t ever gotten a monitor I cared enough to diagnose this far, but the PWM chips create a square wave that gets stepped up in the transformers to drive the high voltage tubes.  The problem this time was bad back-light tubes.  These tubes were seriously blown, though I have come across ones that glow red briefly and then the over-current protection kills the back-light inverter.  Well, I don’t have any spare tubes this size, what about LED strip lighting? that should work, right?

assembled with strips installed

I ordered a 12v LED strip off of amazon and it is pretty nice stuff.  The stuff I bought had a rubberized coating on it meant to be used outside, which didn’t really help, but oh well.  The rest of the mod went as expected, I pulled the tubes, carefully disassembled the panel and fitted the new lights, ran power wires through a switch because I didn’t feel like working out the back-light auto-on feature and powered it off of the 12v tap on the power board.  That simple, I could have done with some better diffuser  but I didn’t have much time to work on this.

monitor off, back-light on, diffusion problem

working. Next patient!

entire disassembly album

Razer Barracuda HP-1 Gaming Headphones mic build

Recently my local area was subjected to what I hear is called a ‘100 year rain’ it is apparently a rain so hard (for a given area) that a storm of it’s magnitude only happens once every 100 years (once again, it is for a given area and what constitutes a 100 year rain would vary from area to area).  My house was not hit terribly hard, the roof leaked in one room which may have destroyed some not-so-valuble crap in my attic that we have now taken as an oppurtunity to pitch said crap, the basement flooded a tiny bit since sometime in the past the sump pump had failed and we hadn’t noticed (this is a whole other story), but certain areas of Livonia had the basements flood entirely.  By entirely I mean there was at least a foot or two of water in the basement, there is some controversy about whether or not the city had the opportunity to direct the storm drains into the freeway to prevent t from happening, whether it was truly a sewage backup, and plenty else that basically sums in up as the city not taking responsibility for their sewer system not being able to handle a ‘100 year rain’ (as I see it they know it will flood once a century and have no plan for that).

I guess that was my small rant for today, I can’t really feel too invested in someone else’s fight against the city since the only way it affects me is that I have some slightly damaged cool new stuff and I helped haul some seriously damaged heavy stuff out of a friend’s basement.  Moving on to the relevant topic for which this blog post is titled, one of the things this friend gave me while I was helping him clear out his basement was a pair of Razer Barracuda HP-1 Gaming Headphones.

My Glorious New Headphones

Since the headset I was using up until now was a 2.5mm mono headset from an old RadioShack telephone this was quite an improvement, but there were two problems: one, the left side was not working, and two, there was no mic.  let’s start with the seemingly difficult part, repairing the left side.  Now, recently I have decided to write a book (or probably it will be a wiki), A long time friend of mine mentioned that we would do something ‘by the book’ when I started to describe some of the mundane details of how I proposed we go about doing something, and after that I proposed we write a book of how we go about doing things.  From generic troubleshooting to favorite torrent sites and programs we use all the time, we would create a manual usable by people who are not us to do things the way we would.  It would kinda be a collective skill set that we have acquired over the years, the main thing that would be at the top of all the lists is ‘Try Re-Seating ALL Connectors!’.  It turns out that these headphones are meant for the Razer Barracuda AC-1 Gaming Sound Card, and it uses a DVI connector to pass all it’s 5.1 analog sound and 5. power to the amp.

That Damned Connector

Going off an another considerably shorter rant, I fully support the use of existing connector styles for tasks completely different from their original intent as long as they can not reasonably be confused with the connector’s new purpose.  Meaning I support the use of the DVI connector on this audio card and these headphones since I find it unreasonable for someone to mistake a pair of headphones for a monitor (also, there’s a key in the connector, a missing pin on the female connector preventing you from plugging a monitor into your sound card and potentially damaging in if they chose to put the 5v on a pin that might damage the monitor).  I do not support someone making a device that outputs 12v on a usb style connector (since they are commonly used for charging devices at 5v).  The key in the connector means that without a modification to the cable one would not be able to use a standard DVI cable to act as an extender for the headphones (not that you need to since they are so long).  The headphones have a small breakout adapter that puts all the audio inputs on to 3.5mm connectors and a usb one for power (the graphics cord comes with a similar adapter that turns it into 3.5mm female jacks).

Said Breakout Cable

Getting back to topics at hand, all I had to do was plug the connector back together (it was not screwed together).  The real thing I actually did to these headphones was building a mic for them.  I cracked open the earphone of the headset using the three phillips head screws located just under the foam of the ear piece, once open it was fairly easy to read the pcb and figure out what the mic pinout had to be.

The mic Jack pcb (more detailed photos in the album)

I don’t know what the original headset did to light up the leds around the jack, but without internal modification to the headset I could not figure out how to light up them.  The tip of the 3.5mm phono connector is mic+, the ring in mic gnd, and the shield is the negative side of the leds that has to be grounded for them to light up, but when I connected the shield and ring together the leds did not go on, it was not until I connected mic gnd to the gnd pin on the leds on the side that the leds on the bottom lit up.

New gnd Wire

I don’t know where the mic itself came from, it was in one of my parts bins with a very long cord on it, and a stiff wire for the last couple inches of the wire.  I chose it for that purpose exactly, I used the stiff wire to hold up the mic, I fastened it to the ring and shield of the 3.5mm connector.

I documented the disassembly process as well as I could and have it posted to my public google photos for anyone else who might find it useful.

https://picasaweb.google.com/Abzman2000/RazerHeadphones?authuser=0&feat=directlink