Toshiba Satellite 440CDT - Laptop Battery Repair

A Toshiba Satellite 440CDT. Scored for the princely sum of $10.

A Toshiba Satellite 440CDT. Scored for the princely sum of $10.

On an adventure to a local... sort of antique/junk/anything store, I found this. A Toshiba Satellite 440CDT - a laptop from the early Pentium era. Complete with battery, featuring an internal CD drive (feat. a forgotten Foo Fighters CD) and internal 33.6K modem, I had to have it, as it looked in fairly decent condition. It also had a 56K generic brand modem in the card slot and no charger. The floppy drive was also absent. 

Upon getting it back to the workshop, I realised I didn't have any DC barrel jacks to fit the onboard Toshiba connector - quite a fat one, and none of my other laptop supplies would fit either. I also determined after some experimentation and judicious use of Google, that the laptop would refuse to power up if given a voltage in excess of 16.5V


A screengrab of Toshiba error codes from

A screengrab of Toshiba error codes from

Unfortunately I only had relatively modern laptop adapters all putting out in excess of 17V. I eventually found an adapter for my old EEE PC 901 netbook, which puts out 3A at 12V. That would have to do. Instead of driving around to find the appropriate connector, I simply soldered a wire to the centre pin of the existing jack for the positive lead, and found a ground point to solder to inside the laptop which I brought out through a tastefully drilled hole. Butchery? Yes. Quickly and tastefully done? ...arguably, also yes. Sometimes you're just trying to have some fun and don't want to get bogged down. I soldered these leads to a readily available 2.5mm DC jack which I have loads of (thanks to the Grav-A) and epoxied it in place.  

I'll definitely come back and clean this up one day. Promise.

I'll definitely come back and clean this up one day. Promise.

So, with adequate power connected, we had success - a whirr from the fans, that lovely '90s hard drive grind, and we were up and running! Greeted by a bit of ScanDisk and Windows 95. However, sadly, all was not well - the battery was showing up in Windows but was reading 0% - and was "charging" but the value wasn't going up at all. I decided to disassemble the pack. I was surprised after pulling stickers off that it was all just plastic pieces, clipped together - no screws were involved. I was able to pull the pack's case off with just my fingernails, without damaging anything. 

I counted 9 cells in the pack. They were in 3 parallel groups of 3, giving a nominal pack voltage of 10.8V. I was surprised to find that not only was each cell reading over 2.0V (a kind of point of no return for Li-Ion batteries) but they were also fairly close to being balanced across the whole pack (important to avoid... fires, pretty much). I decided to manually charge the pack myself. Rather then whipping up a cable to connect it to my hobby Li-Po/Li-Ion charger, I just stuck it on the ol' DC variable power supply, trickling a good 300mA or so into the pack and keeping a close eye on it. I got it up to 11.0V and was thirsty to try it out again - but alas, no. Windows still reported the pack at 0% charge and wasn't budging.

So where does this leave me? A later trip to the junk shop netted the missing external floppy drive and another matching Toshiba battery, which I haven't yet disassembled but an initial test showed the same problem. I'm currently thinking that some sort of onboard EEPROM has bricked the battery but haven't looked too closely into it. A closer look at the battery's PCB might show up something I can play with, but even if there is an EEPROM or similar, it'll be tough to figure out what data's on it and what needs to be changed to get the battery going again. I'm also unable to find any decent hardware info utilities that can give me further info either as Windows 9x software is rather rare on the web now - too old to need in normal use, not old enough to be vintage yet. If you've got any tips or helpful information, hit me up at or leave a comment below!

SSD1306 OLEDs - DMA Library for Arduino Due

That bitmapped logo needs a little work!

That bitmapped logo needs a little work!

Want the library? Find it at Github.

So we're always cooking up hot new hardware in the Grav Corp labs. Recently, we've been working on a project using a 128x64 OLED screen with the SSD1306 controller. Adafruit is a good source of these displays, with an excellent library written by Limor Fried. The Adafruit_SSD1306 library makes it simple to use these displays with a variety of Arduinos, using either software or hardware SPI. However, we wanted a speed boost, and the Due looked like it could deliver, with its DMA (Direct Memory Access) capability.

So what is DMA? Direct Memory Access, as simply stated by Wikipedia:

  1. Direct memory access (DMA) is a feature of computerized systems that allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).

We wanted to use the DMA capabilities of the Arduino Due's SAM3X8E microcontroller to speed up calls to the display() function, which writes the display buffer to the OLED controller. With stock settings using hardware SPI, calls to display() take ~2ms on the Due. This is a long time to tie up our CPU, so what can we do to improve this?

Like all good endeavours, this began with research. We hunted for anything regarding the SSD1306 and DMA but came up short. After digging deeper, we found Marek Buriak's library for ILI9341-based TFT screens. Marek used code from William Greiman, who developed SD card libraries for the Arduino. William took advantage of the SAM3X8E's DMA capabilities to enable faster SD card transfers, and Marek then adapted this code to allow faster writes to ILI9341-based screens. This is particularly useful, as the ILI9341-based screens are full-colour TFT displays, which require large amounts of data to write to. It was then simple to find the code to send a buffer out over SPI using DMA in Marek's code and adapt that to the Adafruit library for the SSD1306.

There is one caveat: as we are configuring the SPI hardware completely differently than usual, it is likely that this code is incompatible with the stock Due SPI.h library (though we haven't tested). This makes it difficult if you want fast writes to an SSD1306 screen AND to use other SPI hardware in your project. There is a workaround - replace your calls to SPI.transfer() with calls to fastSPIwrite() and spiRead(), however this may be buggy at this stage in the library's development and your mileage may vary. Any feedback or testing is welcome! 

What kind of speed boost does this library give? Well, running at the same SPI clock as the Adafruit library (clock divider of 5 for SPI), we speed writes up from 2ms down to approximately 0.5ms. This is great! We can then go even faster by increasing the SPI clock (set divider to 2) and a display() call will only take ~0.25ms for a 128x64 display!

So, if you fancy trying out the library, head over to the Github page here. You can also discuss this library on the Arduino forums! Due credit to Limor Fried, Marek Buriak, and William Greiman who did the hard yards on their respective code. The internet allows great collaboration, does it not?

Finds: Kenwood Stereo

Check out those bling knobs.

Check out those bling knobs.

About a year ago, I found a 90s era Kenwood stereo system going spare. Destined for the trash, I couldn't let it go to waste. It looked in such good condition! Alas, when I did eventually manage to power it up, I was to be disappointed. 

Upon hooking everything up, there was very little working. Sound could be heard very quietly on the right channel, with nothing at all coming through on the left. Playing with the controls showed me that the volume control did nothing until it got to the bottom of its range, and balance was also completely inactive. This led me to suspect the volume control IC, as this stereo has soft controls. 

We initially wasted some serious time thinking we were working with the larger LC7535M. Awkward.

We initially wasted some serious time thinking we were working with the larger LC7535M. Awkward.

After opening up the unit, some investigation and Googling of chip names led me to find the stereo used the Sharp LC7535P, a volume control chip in a rather odd 22-pin DIP package. Already having determined it was non-functional, and pricing a replacement at >$20 on eBay, I decided to remove it completely, and hardwire the input signal to the output pin of the chip to test things (in this case, wiring the pin 1 trace to pin 6 and pin 22 to 17). Success... sort of. There was now a clean, loud signal on the right channel, but distortion on the left. 

Spot the SMD replacement transistor floating in free space. We globbed it in epoxy later to protect it from possible shorts. The red, blue and black leads head to the front of the stereo so we could splice a pot in place of the former volume IC.

Spot the SMD replacement transistor floating in free space. We globbed it in epoxy later to protect it from possible shorts. The red, blue and black leads head to the front of the stereo so we could splice a pot in place of the former volume IC.

Further hunting led to the discovery of a blown transistor on the vertical PCB next to the chip, which contains some of the amplification components. The transistor in question was a strange 100V+ bipolar type, which required the ordering of a specialty part from element14. The nearest replacement we could source was an SMT part, so it was soldered on with a few stiff pieces of solidcore wire and left to hang in free space. More leads were run to the front panel to replace the LC7535 volume control IC with a simple pot taken from the microphone input, which was deemed useless anyway. This allowed the new volume control to seamlessly fit in with the original fascia. There was just one problem. We'd lost all the original knobs and screws. Some fresh bling items were installed on the front panel instead (as shown in the opening pic, which I think look rather happening, don't you? 

Start to finish, diagnosing this problem and then implementing the fixes took around about 3 or 4 hours. The average service tech these days has to charge in excess of $50 an hour just to keep the doors open, let alone feed their family. So, when you add it up, this sort of job on a junked 90s stereo makes absolutely no financial sense to get done, but as a bit of a fun project on a slow weekend, it's certainly enjoyable, and you just might learn something. 

The Grav-A - Pozible Wrap-up


So late in 2014 we were able to fulfill all our preorders for the Grav-A, and this led to some very happy guitarists out there. It was a great ride from start to finish, and we're absolutely stoked to see how much people are enjoying the Grav-A out in the wild. We've got a lot in store for 2015, but for now, we'd just like to thank everyone below for their help in getting the Grav-A off the ground. Pat yourselves on the back, you earned it! In no particular order: Jordan Leekspin Malaka Senenayake Billy Constantine Ian Messenger Frank Boulden Georgia Mansell Clarisse Mariah Trent Worley Max Tulysewski Katherine Brunner Stephanie Skinner Thomas Williams Jordan Cirocco Belperio Brett Pike Chris Harrison Gavin Artz Andrew Auld David Tim Edwards Rowan Sanders Daniel James Lewis Wundenberg Alex Hoeper Tamsyne Smith-Harding Daniel Gunn Dashiell Dunn David Ozols Paolo Cardelli Michael Tran

You guys rule. Stay tuned in 2015 for more Grav, and at least double the Corp.

Strange USB Cable

So in my travels today, I found this. It's a 1.5m long, coiled, USB A male to USB A male cable. And I can't for the life of me figure out what it's for, other then potentially damaging the two devices you plug into either end of it!

I'm aware that there was a standard for an obscure "USB network" type device - USB A male on both ends for connecting computers together (wonder if there's Linux driver support for something that obscure? Has to be). But that requires intermediate circuitry to do - this is just a straight cable, USB A male to USB A male. If you have any idea what it's for, share your thoughts in the comments!

EDIT: Apparently there is a bunch of dodgy hardware out there that does use this sort of cable to connect to a PC! Thanks to the Hackaday commenters for the reports. 

Vox VT-50 Repair


Around the lab, we like to use a Vox VT-50 amp to try out our designs. It's a cheap, mostly solid-state amp that nobody will miss if something goes horribly wrong. This example has had a hard life, being dragged out to gigs and from workshop to workshop over the years, and recently developed a problem - sound was heavily distorted and intermittent. It was time to open it up and take a look inside.


The VT-50 comes apart fairly easily. Like most guitar amps it's fairly easy to service. The VT-50 is somewhat unique as it's part of Vox's Valvetronix line - using a valve in the preamp stage for more "genuine" tone. The power amp is solid state, however. IMG_20141026_134632_053

The first stop was the input board. The main jack tore pads off the input PCB during disassembly. This is a poor design - a chassis mount jack wired to the main board would have been more expensive and time consuming to build, but more reliable over time. PCB mounted jacks often suffer problems with pads pulling off the board over time. This was fixed up, however the problem continued.


The true culprit in this case was the main solid state amplifier chip, seen here mounted to the heatsink in the center of the photo. One of the legs had broken and was making intermittent contact with the solder pad on the bottom of the board. A small length of a component lead was inserted into the hole, reinforcing the leg and was soldered between the pad and the chip. Since then the amplifier has been running nicely!




Grav Corp featured in Advertiser newspaper; AdelaideNow

We woke up on Monday to the pleasant news that we were in "the paper"! Thanks to the Advertiser, Adelaide readers got to read about the Grav-A and where we're heading for the future. Eagle eyes will also notice that's the Kramer we restored on the blog! Good times. Our thanks to Sarah Spencer for the article, which you can read here.


Guitar Mod - Joshua Calligeros - Sincerely, Grizzly

vlcsnap-2014-10-21-10h22m06s94In September, Josh (Sincerely, Grizzly) came to us with a Jazzmaster and an idea - a guitar-mounted microphone, activated by an arcade button. We made it happen. Check out the video below. Josh's Jazzmaster has had a couple of subtle mods already. Like many others, Josh found his sound with the Jazzmaster and didn't want to mess with it. The stock switches have been removed, leaving plenty of space in the body. A Fender Bullet neck replaced the damaged original, and a Mastery bridge improves upon the "vintage" Fender item which has issues with string skip when you play like you mean it.

This was a relatively straightforward build electronically (watch out for impedance, kids!),  but required some careful thought about the placement of controls.  could be removed to make space for the mic and arcade button - a gloriously vintage way to activate the mic for screaming goodness.

Online Store - LAUNCHED!

It is with great pleasure that we can announce the launch of our online store! This has been a long time coming, and now you can get your hands on a tee, pick up a preorder on the Grav-A, or check out some of the other interesting things we'll be throwing up over the coming months.

To celebrate the launch, for the next week, all items on the store will be at their original Pozible campaign prices! Get in quickly for this earlybird special. We look forward to bringing you more handcrafted audio goodness in the future!

Crowdfunding Success - WE DID IT!

So after a long and energetic campaign, we reached our Pozible goal! The Grav-A is becoming a reality! We'd like to throw out our thanks to all our supporters who helped us achieve this amazing goal.IMG_4089fix If you missed out on the campaign, you'll still be able to get your hands on Grav Corp gear for yourself - keep an eye out for our online store launching soon!

Now, we roll on into production...

Half-Hour Hacks - EHX Screaming Bird

IMG_20140809_164748_976 The EHX Nano Screaming Bird is a reissue of a 70s EHX design. Personally, I've not been a fan of mine - it's far too screechy and has dumptrucks full of high-end and not much else on my setup. I found myself kicking about the workshop with a little time to spare, so I decided to do a quick mod I'd read about online. This allows an easy conversion to LPB-1 spec, turning the treble-boosting screaming bird into a more useful flat booster.



Like most current EHX pedals, it's true bypass, solidly built, and a minor pain to wriggle out of its enclosure. It's also using a fair few SMD components. However, most interesting is the PCB. What's up with those unpopulated pads? IMG_20140809_165457_099

This board is labelled as the "EC-D55 Rev. A". Near the potentiometer, it can be seen there's another set of 3 pads, labelled for a 10k pot as opposed to the 100k installed here. This is noted for the "EC-D56" design, the 100k being used for our "EC-D55" and also the "EC-D12". A quick Google wasn't conclusive, but I'd put my money on EHX using the same board and layout for not only the Screaming Bird, but the previously mentioned LPB-1 (I'm betting EC-D12), and the bass-boosting Mole (I'm betting EC-D56).  On the opposite side of the board, we noted the unpopulated pads, labelled with different model numbers for the slight differences between different circuits. The EC-D55 Screaming Bird and the EC-D12 seem to share the most likeness.


To push the Screaming Bird closer to LBP-1 spec, simply change the two 2.2n caps (C12 and C13) out for a couple of 0.15uF caps.  I couldn't find two 0.15uFs, and in the spirit of "getting it done", chucked in a 0.15 and an 0.1. The great thing about audio electronics is that this is generally just fine. Worst case, I'll swap it next time. There are also a couple of resistor values different between the LPB-1 and Screaming Bird but they're pretty minor changes - we're just trying to get closer, not exact. It'd be trivial to swap them if you're feeling picky.IMG_20140809_174514_763

Put it all back together and whack a nicer knob on it. I never really liked the basic EHX round one and it was jammed on way too tight anyway. All in all this was a fun little hack that only took 20 minutes, and has given me a pedal I'm much more interested in using! Try it out yourself, or let us know about your own mods in the comments!





Half-Hour Hacks - Watercooled Antminer U2

IMG_20140710_161429_685 Cryptocurrency is a pretty hot topic lately, and can be a profitable endeavour for some. For others, like myself, it's a fun hobby. Something to leave running in the background and tinker with from time to time. After a few weeks of GPU mining Dogecoin on my laptop with middling results, I decided to drop $30 on an Antminer U2 on eBay.

Initially, I was able to get a stable rate of 2.2GH/s by basic overclocking. Any higher and the gains in hash rate were offset by excessive hardware errors. To this end, I decided to explore the possibilities of enhanced cooling.

The Antminer's design is neat and tidy, with a single aluminium heatsink. I came up with a simple concept - rather than build a replacement heatsink with a waterpump and radiator, why not just take advantage of the stock heatsink and turn it into an open reservoir for ice cold water? As long as the miner isn't bumped and the design is sealed properly, risk of water damage is minor. In the worst case, I accidentally spill water everywhere, ruining my old broken laptop and a $30 miner ASIC that isn't fast enough to be profitable anyway.

My plan was simple - seal the boltholes holding the heatsink to the board, and then attach four walls to the heatsink to hold water. I used 5-minute epoxy first to seal the holes, before using some sandpaper to roughen the edges of the heatsink to help bond the walls later. I also covered the solder joints for the USB connector to avoid my new walls shorting anything out.


Next, I grabbed some scrap aluminium plate and cut out some walls for the four sides of the heatsink. This was done quick and dirty with a hacksaw, but using a lasercutter or a 3D printer to do this project would be really great.


I wanted to start and finish this in half an hour, so I got inventive. After quickly roughing up the original heatsink with some sandpaper, the new walls were tacked in place with superglue, before applying 5-minute epoxy to seal the edges. More superglue was dripped into the edges of the heatsink to ensure a watertight seal between the walls and the original heatsink.


After waiting for the epoxy to dry and tentatively testing it for water tightness, it was ready to go. The reservoir was topped off with water and an icecube, and CGminer fired up.


Thus far, the U2 has been stable at 2.2GH/s both with and without watercooling. Over the coming days, overclocking will be attempted to see if 2.5GH/s is within reach.

While this project (or a single Antminer) is completely unprofitable as far as mining goes, it's a bit of fun to experiment with. Leave your own mining mods in the comments!

The Grand Oscilloscope Find!

A friend and I just happened to be enjoying lunch in the city when we happened across the most magical of things - an E-waste Recycling dumpster filled to the brim with equipment! Sadly, we lacked transport and also, who really needs a pile of old office computers anyway? Unless you're trying to build your own supercomputer cluster under your bed, of course. Alas, before we could decide on what to take (difficult when you can only carry so much!), a staff member came to shoo us away. However, I had the temerity to ask what her actions would be if I were simply to grab what I could and run. Kindly, the staff member admitted she was probably not going to react. Thus grabbed the scopes and made a swift exit. oscillo_03oscillo_06 We'd managed to leg it with two BWD 820 scopes. There was slight damage to both - one was missing a button, the other missing a chunk of its timebase dial. From what I gather, they were built by an Australian manufacturer in the 1970s, perhaps very early 1980s. It was easy enough to reattach new plugs to the power cables and we were ready to power up...

oscillo_04 oscillo_05

...and we had moderate success! No loud pops or bangs, and the magic smoke seemed to still, largely, be inside. The left scope, missing a button, appears to otherwise be in working order, displaying both channels appropriately. However, the right scope, with some damage to its timebase dial, does seem to have an issue with one channel not displaying properly at all, showing noise and inconsistent responses to input. Further investigation is warranted, but this is a find I am most happy with! Always good to get some interesting equipment on an e-waste run, rather than another hundred old TVs and discarded phones...


EHX Big Muff - Various Mods

So we've done a fair few mods lately of Big Muffs for people, mostly to the V8 Russian Big Muffs. We've thrown up a few pictures here so you can get an idea of what you'll see inside, and what to expect. EHX make some great pedals, and I'm a big fan of some of their ideas. muff1_1

Most commonly, people bring us the Russian Big Muff, asking for a true bypass mod. We normally throw in an LED swap for a high-brightness blue, which is much easier to see than the stock red LED, and let's face it, it looks pretty cool.


It is unfortunate that EHX tried so hard to save money on the modern V8 Russian Big Muffs. They're a great sounding pedal, much more of a warm overdrive tone compared to the NYC reissues, and they definitely have their own relevant place in the Muff lineup. However, the stock bypass is absolutely terrible, sucking big fat gobs of tone out of your signal. I don't know many people that would ever use one stock - the tone loss is incredible. However, with the true bypass mod, these things are fantastic.



Other mods we've commonly performed are boosting the gain of the circuit (we favour swapping the emitter resistors, tastefully, for lower values) and adding DC jacks to the rear panel (because who wants to buy 9Vs every six months?). They're a great pedal to work on, with only four screws to remove, and everything slides apart and is mounted to the front panel. We've also done pot replacements, normally to higher-grade Alpha units. If necessary, the stock knobs (which are a set-screw type) can be drilled out to accept larger-shafted pots if you wish to keep the original Russian look.


For interest's sake, we've also looked at working with the current models from EHX. These are much higher quality than the aforementioned Russian pedals. These can be had for under $120 AUD at the moment and sound pretty fantastic, with the classic high-gain NYC sound. I've taken apart my own Big Muff Pi with Tone Wicker to take a few pictures and to get an idea of the construction.


Note the two switches on the front panel. These are PCB mount DPDT types, of a kind not easy to find for the home builder. One is to disengage the tone circuit, a common mod often featured on boutique clones. This gives a slight volume increase, though not major, as the Big Muff has always featured a gain stage to recover the losses through the passive tone control. It gives a much fuller, more open sound when the tone control is disengaged.


The second switch is to engage the Tone Wicker. The switch controls a 4066 quad-switch IC to engage/disengage three high frequency filters that alter the tone of the pedal, giving a more brittle, fizzier sound. EHX clearly chose a cheap DPDT switch part and paired it with a switching IC, as they deemed this cheaper than trying to specify a 3PDT toggle. I can also only assume they specified DPDTs for both switches where SPDTs would suffice in order to add strength, as the DPDTs are soldered to the board with two rows of three pins, adding rigidity. The board is held in place by the right-angled PCB mount 16mm Alpha pots, which aren't visible from the side of the board shown above, and the Neutrik input and output jacks. Note as well the cutouts in the PCB board just above the jacks. These allow the board to flex for installation. This board is very difficult to remove from the case, however, as the pots, audio jacks, or the DC jack tend to snag on the case when one tries to remove it. All in all however, I quite like the construction of this pedal - it is very robust and probably very cheap to make thanks to the SMD parts.

I found the EHX pedals to be very educational as to pedal design and construction. It led me to realise many improved techniques in my own designs. Try disassembling some of your own pedals - you can learn a lot from the mistakes and successes of others!

Vox V847A - Pot Replacement

A friend of mine had a Vox V847A wah pedal, that had an all too common problem - a scratchy pot, making the pedal virtually unusable. It was a simple, if expensive, fix. v847a2

Best practice is to replace the pot entirely. I ordered in a Dunlop Hot Potz II 100K. This is far more reliable and is sealed well against dust ingress. It's a popular replacement part for a wide variety of wahs on the market.



It was a relatively easy replacement. The original pot was unbolted from its mount to the frame, and then desoldered from its board. Wires were then used to connect the Hot Potz II to the original board, as it does not of a PCB mounting type like the original part. Once the new pot was bolted in place and the rack readjusted to suit, the wah was ready to go again!