Buck convertors, power supplies, motherboard power rails and laptop repairs.

If you have any interest in repairing laptop motherboards, you have likely spent many hours watching videos on Youtube. Here the experts with years of experience, are quickly showing how it’s done, with little explanation of what’s really happening.

For the beginner (like me) this can be both fascinating and frustrating. The lack of information aimed at people just starting out, coupled with a steep learning curve is daunting.

Power rails and buck convertors – the penny drops

But, if you watch enough videos the penny drops and things slowly become a little clearer.

Videos on two repair channels really helped me understand why Loius Rossman keeps mentioning PPBUS_G3 HOT in his Macbook repair videos and how buck regulators.

Adam from channel AdamantIT explains buck regulators in this video, and look out for his board repair basic playlist which goes into further detail about power rails.

Sorin from Electronics Repair School always starts at the jack plug too, he explains power rails and what he’s looking for in this video.

But what do you do if you want to poke around a motherboard without risking your own laptop?

Well I found a great example of power rails and buck convertors inside a Virgin Media Superhub 2.

If you’re in the UK there’s a good chance you have one laying around after you have upgraded, or know someone who has an old one hiding in a cupboard.

Here is a very simplified view of the power rails.

Mosfets and coils
VM Superhub 2
Motherboard or Virgin Media’s Superhub 2

Power rails 1.0v, 1.8v, 3.3v and 5v can be found bottom right

All of the power rails are clearly labelled with their respective output volts, 1.0v, 1.8v, 3.3v, and 5v.

Buck regulators
Power rails are clearly labelled

With the help of a multimeter you can explore the board from the 12v supply and probe the inputs and outputs of the various supplies to help get a better understanding of how things work.

The benefit of using a working one, is that you can see how they are supposed to work, rather than blindly probing a dead laptop motherboard, wondering if what you meter reading is correct or not.

Well I hope you found this post useful and good luck with your fixing.

Chips on the board include…

Winbond W971GG6KB-25
1GB DDR2 Memory requires the 1.8v power rail.

E523TH52 DNCE2530GU
Intel Puma CPU – I can’t find the voltage or the datasheet for this chip.

Qualcomm Atheros chip

Qualcomm ethernet switch

ESMT M14D5121632A (two chips)
8MB DDR2 ram hidden beneath cover, require 1.8V

Spansion S34ML01G200TF100
Cypress Semiconductor flash memory

Bush Dab Radio power jack repair video

This morning I recorded my first ‘fix it’ video when attempted to repair a faulty power jack on a Bush Dab radio.

The radio was donated to me, after the previous owner had tried and was unsuccessful to find a lasting solution.

Expecting it be a dry solder joint, my first plan to re-flow the solder, ended with snapped wires and lots of time lost removing old glue holding the power jack in place.

Watch the video below to find out what I should have done first.

Tools used during this fix.

Soldering Station 937D+

Helping hands, great when soldering small parts

GHD 4.2P Repair Success

Apparently GHDs are a girl’s best friend, so when my girlfriends pair developed a fault, I had the chance to earn some brownie points, if I could fix them.

GHD 4.2p
GHD 4.2P

One main problem with ealry 4.2 models is the swivel connector. It’s poorly designed, so if you have a pair that is crackling and popping, then you probably have an old model and you should have the cable and socket upgraded.

Old mains cable and 3 pin socket
Old mains cable and socket on early GHD 4.2 needs upgrading
Replace socket for older GHD 4.2 modles
New upgraded swivel mains adapter and socket

Another simple fix is either replacing the temperature fuse and / or the heating elements. I tested both using a multimeter, the fuse (brown wires) showed it had continuity and the element (clear wires) gave a reading of around 60 Ohms.

Checking temperature fuse and elements
Continuity and resistence testing the fuse and element

With the fuse and both elements checked, I moved onto the R11 and R8 resistors. R8 was working but R11 didn’t give any reading.

R11 and R8 GHD resistors
R11 and R8 resistors

I choose to replace both resistors with new ‘Melf Resistor 50/47 Ohm’.

Sadly it didn’t go as planned and I burnt off one of the pads. Luckily it was pad closest to the screw terminal, so it was a simple case of creating a small jumper wire from the screw terminal to the resistor.

Resistor with jumper wire
New melf 50/47Ohms resistors with small jumper wire

Success. With the new mains cable and resistors the GHD straighters are working.

The mains cable cost £11.49 and the resistors were £1.99 for 10. When you consider a new pair of GHDs are priced at over £100, spending less than £15 to attempt a fix has been well worth the effort.

Now, where’s my brownie points?

Hitachi DV18DSDL Drill Driver attempted fix – fail

Having watched multiple youtube videos of people successfully repairing old and broken power tools, I decided to give it a go myself.

Because I wanted an 18V drill driver for myself I went to ebay and picked up a faulty Hitachi DV-18DSDL for £20.

An initial inspection found no brushes were fitted. Could it be a simple case of fitting new brushed and having a working drill?

Missing brushes

Sadly no. Trying to fit new brushes into the old brush house resulted in a broken brush. So the next option was to order a new brush housing, which came with brushes and brush covers too.

Replacement brush holder

Soldering on the new brush holder wasn’t a problem, but I did notice the red/black wires were on the opposite sides on the new one.

I ignored the colours and kept the brushes on the original side of the switch connector. Had I swapped them over, the forward switch would have ran the drill in reverse and vice versa.

With a new brush holder and brushes, the drill still refused to work, so I turned to youtube and looked at how to fault find the armature.

Using a multi meter and bit knowledge, I found the armature had two broken circuits. This happens when the copper wires have snapped.

Hitachi Broken Armature

Buying a replacement costs around £40, which isn’t economical, so the drill will have to be put to one side and perhaps used for spares, or split up and sold on as parts.

Another option is remove the copper windings and rewind it. I plan to do this when I come across an old motor with the correct sized wire.

Lessons learnt.

Check the armature first, before paying out for any other replacement faulty parts.

Stripping down my Helvetia gents watch – Part 1

This is a series of posts where I’ll be stripping down and cleaning an Helvetia gents watch.

Being my first attempt at horology, I don’t expect things to go straight forward but let’s give it a go.

Here are the tools i’ll be using for the project.

  • Basic watch movement holder
  • loupe
  • brass tweezers
  • 0.8mm, 1mm, 1.2mm precision screwdrivers


Step 1 sees the movement removed from the case, there’s normally  small hole to release the winder (crown), the pointers are removed next and finally the watch face itself. You’re left with the movement, ready to be dismantled.