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SERVICEMAN’S LOG Turning a pile of junk into computers Bruce Pierson of Dundathu, Queensland, repairs many laptop/notebook computers. He often gets them inexpensively (or even for free) because they’re broken, then uses parts from one to fix another. Here are several stories of computers he’s fixed lately... I have a few old laptops that I have installed various versions of Linux on to try out. Among these is a Compaq CQ60 that was my younger daughter’s first laptop. The last time I looked at it, it had a stuck key, causing it to beep continuously while on. Fixing that would require replacing the keyboard. I got it out recently and looked through my box of keyboards that I had salvaged from old laptops over time. I still did not have a keyboard that would suit this laptop and was reluctant to spend $25 to buy a new one for a device I’m not using. I then noticed that one corner of the keyboard surround near the screen was sticking up. I checked under the laptop and the screw was in place, so something must have broken inside. I removed the screws on the bottom that held the keyboard surround on and found that the brass nut had broken out of the post in the corner that was sticking up. I considered how I could repair this part. I decided to get out my 40W soldering iron to heat the brass nut and press it into the now shorter post. That worked, and I put the screw in to make sure it sat vertically. A bit more heat allowed me to true it up. Now I would need a longer screw for this corner. I looked through my laptop screws but I had nothing longer than the original screw. Then I remembered that several years ago, someone had given me a small parts cabinet with around 30 small drawers 98 Silicon Chip in it. I looked through the drawers; most of the parts were for PCs, but I found some laptop screws. They were mainly short, but in another drawer, I found one that was exactly the right length. I refitted the keyboard surround, but when I went to use the replacement screw, I discovered that the head was a larger diameter and it would not fit in the hole. So I put the screw in my small electric drill and, with the drill running, I used a file to reduce the diameter of the head, checking it periodically against the original screw to get the diameter approximately the same. With the screw modified, I was able to install it and now the keyboard surround is fitting correctly. Now I just need a good keyboard to get it back in working order. Toshiba C50D-A screen replacement Recently, a friend asked me if I could have a look at his Toshiba laptop. It had a round ‘black hole’ in the screen that was becoming increasingly annoying. The laptop was fine apart from this. I have seen some weird things with faulty screens in the past, but this is the first time I’ve seen one with a black hole. The cost of a new screen was over $90, so he wondered if I might have a good screen from an old laptop that would fit his. As it happened, I had recently disassembled a Toshiba L650 laptop that no longer worked, and I still had the shell and screen sitting on a shelf. I did some online research and found that both laptops use exactly the same screen. I started by removing the battery, then the RAM and HDD cover, and I took out the hard drive and RAM. Then I removed the optical drive plus the 15 screws securing the back shell, allowing me to remove the back shell. Australia's electronics magazine siliconchip.com.au Items Covered This Month • A tale of four computers • Repairing a Hisense 65U8G power board • A faulty IR sensor in a carport Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com This laptop is very unusual in that the bottom shell comes off, leaving the motherboard in the top panel, whereas with most laptops, the top panel comes off, leaving the motherboard in the bottom shell. I could see that I would need to remove the motherboard to detach the cable going to the screen. This meant removing the keyboard. That turned out to be a nightmare with the way the keyboard is fitted into the top panel, but I finally got it out and unplugged the cable. Next, I removed the CPU fan and I was surprised by the amount of junk that was almost entirely blocking the fins on the heatsink. It’s a wonder the laptop had not been overheating; it was one of the worst I’ve seen. I unplugged all the plugs in various locations around the motherboard, then removed the single screw from the motherboard and lifted it up to unplug the video cable. After removing the motherboard, I cleared the rubbish off the heatsink and cleaned the small amount of dust off the fan. After removing the last two screws from each of the hinges, I had the lid with the screen free. Removing the two screws in the bottom front corners of the screen allowed me to prise the inner surround free from the lid. Then I noticed a problem. On one lower corner of the lid, the two small brass nuts had come out due to the old plastic becoming brittle over time and breaking. There was no easy way to remedy this situation. There would be no way to secure the hinge on that side to the lid without coming up with a solution. I did not have a spare lid for this laptop. My friend asked me what I could do to get the repair completed, as this laptop was very useful to him. I said I could put two screws through the lid from the back to secure the hinge, but that he would see the screws in the back of the lid. He said that he wasn’t concerned how the lid looked from the back. So I got the screen from the L650, unplugged the cable from it and removed the hinges. Then I did the same with the original screen and I fitted the original hinges and original cable to the replacement screen. With the screen re-fitted to the lid, I lined things up, drilled the two holes through the lid and then lightly countersunk them on the outside of the lid. I had to find two small screws and nuts that were long enough to do the job. This is not easy, as laptop screws do not commonly come that long. But with some searching through my containers of laptop screws, I found two suitable ones. I used the two small brass nuts that had come loose from the lid to fit the screws in the lid. This ensured that the hinges were in the correct place. I eventually found two tiny nuts to finish the repair. I fitted one to the screw through the hinge, then I replaced the surround and screwed the last nut onto the screw in the corner of the screen. The very dirty Toshiba C50D. siliconchip.com.au Australia's electronics magazine May 2026  99 I could now reassemble the laptop. I fitted the two screws to each hinge to hold the lid onto the laptop, then I connected the screen cable to the motherboard and sat the motherboard back in place. I screwed in the single screw that holds it to the top panel. I connected the rest of the cables to the motherboard, then put the CPU fan in place and installed the two screws that hold it to the motherboard, and plugged in its cable. I sat the back shell in place so I could turn the laptop over and connect the keyboard. I plugged in the keyboard cable, then I had a lot of trouble getting the keyboard back in place. I have never had this much trouble removing and refitting a keyboard on any other laptop previously. But I got it correctly fitted in the end. I closed the lid, turned the laptop back over and screwed the back shell on. Then I fitted the hard drive, RAM and optical drive. I replaced the cover for the hard drive and RAM, and installed the battery. I tested the laptop and everything was good with it now. I gave the keyboard a quick clean. My friend was really happy to see his laptop nice and clean, no longer with a hole in the screen. While it may not have been a cosmetically perfect repair, at least it saved the laptop from being scrapped. HP 15 Notebook RAM upgrade I wanted to try Windows 11 so, using a Windows 10 laptop, I downloaded the Windows 11 25H2 ISO file and used Rufus to copy it to a 16GB flash drive. I had an unused HP laptop but it won’t boot from a flash drive, like many later PCs will, so I had to run the setup from inside Windows 10. This laptop had no personal information on it, so I just wiped everything and started fresh with Windows 11. The installation went smoothly until I got to connecting to the internet. I knew that if I connected to the internet, that I would have to log in with a Microsoft account, which I did not want to do, as it would be a massive inconvenience to need internet access every time I wanted to log into Windows. I got to a command prompt by holding Shift and pressing F10, and I entered the command “oobe\bypassnro”. This initiated a reboot, and it then showed “I don’t have internet”, so I could log in with a local account, just like in Windows 10. At the Windows 11 desktop, the first thing I noticed was that the start button was in the middle of the taskbar, which was impractical. I found the setting and changed it back to where it should be. Then I found that many of the usual features were missing from the taskbar. I did some searching online and I found a way to fix this. I found Explorer Patcher and tried to download it using Microsoft Edge, but it would not complete the download, stopping before it was completed. So I downloaded and installed Google Chrome and then I was able to download Explorer Patcher and run it. That fixed the taskbar and I was then able to put Quick Launch back on it. This HP laptop only had 4GB of RAM, which is very low for Windows 11. I wanted to upgrade the RAM to 8GB. This HP laptop is one of those laptops that must be completely dismantled to replace the RAM or change the hard drive, which makes upgrading or changing anything difficult. With the top panel removed, I had to remove the motherboard to find the RAM. At this point, I was becoming concerned that the RAM might be soldered to the motherboard and not be upgradeable, as I’ve found this on some laptops previously. But after removing the motherboard, I found that there was a single 4GB RAM module in a slot, so it could be upgraded, unlike the soldered CPU. Now I needed an 8GB RAM module. I still had several old, non-working laptops, so I started by checking all the The HP 15 motherboard; the RAM is next to the CMOS cell. 100 Silicon Chip Australia's electronics magazine siliconchip.com.au HP laptops, but I did not find any 8GB RAM modules. Then I also checked other brands of non-working laptops and I removed several hard drives and RAM modules, but I still had no 8GB RAM module. Then I found an Asus F553M laptop that was another one of these laptops that needs to be completely dismantled to access anything. I dismantled it and it had one 8GB RAM module. I got my Dell laptop that has Linux on it and I removed the two 4GB RAM modules and installed the single 8GB RAM module. Running MemTest86+, it went through the entire test with no errors, so I knew that I had a good 8GB RAM module. I then installed the 8GB RAM module in the HP laptop. Next, I decided to check the CR2032 cell to see what condition it was in. I first tested it with my multimeter and it read 2.97V, a sure indication that it had reached the end of its life. I got out my dedicated cell and battery tester and checked the cell and it read 1V, 0%, so it needed to be replaced. The new cell measured 3.2V and 100%, so I fitted it to the laptop motherboard. It’s always a good idea to test replacement cells to make sure they are still good, as some cells may be getting old and losing their voltage, which happens over time, even when a cell is not being used. Some laptops have the CMOS battery (cell) located in a convenient location under one of the covers, usually the RAM cover. But a lot of laptops have it in a location that is not visible, and it’s necessary to dismantle the laptop in order to replace the cell. Some laptops even have the cell soldered to the motherboard, but these are mostly rechargeable cells and they don’t normally need replacing for the life of the laptop. With the laptop reassembled, I could see that the battery had started charging after sitting on 0% for some time while I had been using it. Laptop batteries that have been sitting around for a long time will usually go flat. Often they will not charge up again, but in some cases they will come good if left on charge for a long time. I ran msinfo32, which brought up the specifications for the laptop. This is a very handy command for finding out just what’s inside a laptop, as it shows the CPU, hard drive, RAM and many other details. Compaq CQ42 CPU upgrade I was setting up a Compaq CQ42 to run Linux when I found that the CMOS battery (cell) was flat. It would be a big job to change the cell, as the laptop would need to be completely dismantled and the motherboard removed to access the cell. Unfortunately, this is another of that frustrating class of portable computers that has the CMOS cell mounted in an inaccessible place. So once again, I’d have to totally dismantle it to complete the swap. Seeing that I would have to go a lot of trouble just to replace the cell, I thought I would upgrade the CPU while I had it apart. It had a Celeron T3100 at 1.90GHz; I had some spare CPUs that I’d salvaged from dead and defective laptops. I started by searching through the CPUs that had the same socket (PGA478). I set aside any processor that was faster than 2GHz – I had four. Next, I checked which CPUs were compatible with the CQ42 motherboard. I found the siliconchip.com.au Australia's electronics magazine May 2026  101 I figured that while replacing the CR2032 cell in this Compaq CQ42 laptop, I could also replace the CPU, best option to be a Pentium dual-core P4500 at 2.3GHz, as it was listed as the most common CPU in the CQ42. I had a faster 2.4GHz CPU but it was not compatible. The first step was to remove the battery and the cover for the hard drive, then the cover for the RAM. Next, I removed the optical drive. I first opened it with an optical drive eject tool so that I could pull on the tray and not the front panel. Then I removed the WiFi card after removing the mounting screw and unplugging the two wires. Next, I removed the three screws holding in the hard drive and unplugged the connector. Most hard drives are not held in with screws like this one. Many laptop keyboards are held in with small clips at the top or bottom of the keyboard, or occasionally screws at the top of the keyboard that are accessible after removing a panel. The CQ42 is quite different in that the keyboard is held in by six screws from the underside. I removed the six screws and then used the optical drive eject tool to push up on the keyboard through one of the screw holes. This allowed me to lift up the keyboard, disconnect the cable and lift the keyboard clear. I then removed the remaining screws on the bottom of the laptop and the one screw under the keyboard, unplugged the four cables and prised the top panel off. Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 102 Silicon Chip After removing one screw holding in the CPU cooling fan and two holding in the motherboard, I unplugged all the cables and lifted out the motherboard. I could then unscrew the six screws holding the heatsink and fan to it and remove the heatsink with the fan still attached to it. Then I cleaned the old heatsink compound off the CPU heatsink. I fired up the compressor and blew compressed air through the fins of the heatsink. Quite a lot of junk came out, so it was definitely in need of cleaning. I also cleaned the fan’s fins with a damp, squashed cotton bud so that the assembly would be ready to refit after changing the CPU. I changed the CPU, applied new heatsink compound and reinstalled the heatsink. Then I changed the CMOS battery (cell), which was the main reason for completely dismantling the laptop. With that done, it was time to reassemble it. I put the motherboard back in the bottom shell and installed the two screws to hold it in and the one screw to hold in the CPU cooling fan. Next, I reconnected all the cables, put the top panel back in place and connected the four cables that were in the top shell. I installed the one screw in the top shell and all the screws in the bottom shell. I then plugged in the keyboard cable, put the keyboard in place and reinstalled the six screws from the bottom. After reinstalling the WiFi card and connecting its two wires, I refitted the optical drive and installed the screw that holds it in place. Then I plugged in the hard drive connector, sat the hard drive in place and drove in the three screws. I put the hard drive cover on, installed one 2GB RAM module and put the battery back in. The battery was not charged, so I connected a charger and pressed the power button. I tapped the Esc key and then I pressed the F10 key to access the BIOS setup. I set the time and date, then checked the other settings before exiting setup and saving the new settings. Now that I was ready to install the operating system, I switched it off, inserted the other 2GB RAM module and Australia's electronics magazine siliconchip.com.au put the RAM cover back on. I considered upgrading the RAM to 8GB, but I decided not to, as Linux is pretty light on RAM usage and I would only be using it for web surfing and research. I had already set the laptop to boot from the optical drive as the first choice, so I booted from the PearOS Monterey installation DVD. Installing Linux on these old laptops gives them a new lease on life. It can fit on a 40GB hard drive, but I usually use 120GB or larger. Hisense 65U8G power board repair This LCD TV has a dimmable LED backlight, using more power than a normal LCD TV with a simple backlight. The advantage is higher contrast (stronger blacks). An LCD panel does not fully block the backlight, so the blacks appear dark grey. By selectively switching off the backlight elements, the blacks are more black. In the future, RGB panels, with a matrix of red, blue, and green LEDs, promise to provide a high-contrast screen better than OLED TVs. The power board in this TV has a power factor correction (PFC) stage using an IPD2308 IC that makes its current draw more sinusoidal, in phase with the mains voltage waveform. The normal capacitor input supplies used in LCD TVs take large spikes of current at the peak of the mains voltage and are not popular with supply companies. This PFC circuit is unusual in that it uses two transformers, each driven by a separate input Mosfet, although both Mosfets are driven by the same IDP2308 chip. I think this is done because it’s easier to fit two smaller transformers than one large one. The outputs of the two transformers are connected so that only one Mosfet half-bridge is required on the output side. The power fuse to the board was blown, and both the input Mosfets were shorted. The input Mosfets share the same 0.05W current-sensing resistor (3 × 0.15W in parallel). These were blown open. The circuits driving the input Mosfets were damaged as the Mosfets shorted, and the IPD2308 was also destroyed. Each Mosfet had a PNP emitter-follower transistor to speed up its switch-off. Surprisingly, the PNP transistors survived, but two resistors in each driving circuit were open-circuit. So quite a few components to replace. As the IC and resistors are surface mount, you need a hot air gun for the IC and hot tweezers for the resistors. So you have to decide whether to repair or buy a second-hand board on eBay or similar. Roger Sanderson, Sinnamon Park, Qld. IR motion sensor repair We have a sensor in our carport looking at the driveway to detect visitors as they enter the property. This is necessary as the driveway is not easily seen from inside the house. The sensor is a simple infrared motion detector (transmitter) with a separate light/beeper box (receiver) to provide an indication of activity in the driveway. The units are connected wirelessly and run off batteries that seem to last forever. I bought the unit from Altronics, and it has proved reliable and just the right solution for the job. After many years of flawless service, the unit developed siliconchip.com.au an intermittent fault. The lights in the receiver would flash when triggered, but the audible alarm would not sound. As the beeper unit normally sits on the hall table where it can’t be readily seen, this was a problem. I assumed the transmitter unit was working correctly. I duly inspected the receiver unit, replaced the batteries, and the beeper came back to life. Good! The unit was put back into service and continued its duties until the beeper failed again several months later. This time, I took the back off the receiver and gave it a thorough inspection. It was a fairly simple construction, a main printed circuit board with a small wireless receiver board soldered to its side. Nothing was obviously amiss. I touched up a few possibly cold solder joints, but still no sound. Checking the loudspeaker, I found it was fine, measuring 95W and producing a healthy click each time the meter probes were attached. I removed a transistor that seemed to switch the input to the audio circuits and tested it, but it was reported as working correctly, so I returned it to the circuit. Various other components were checked in-circuit with nothing obvious showing up. Fortunately, most of the components were marked with their values, and that allowed easy checking. As I worked through these components, it came to the point where a small IC on the board was the only untested component in the beeper circuit. I could not figure out what it actually did; it had an obscure part number that failed to show up in web searches. At that point, I decided it was time to give up and look for a replacement driveway detector. After much looking around at various modern equivalents that had up to 50 tones, pushbuttons galore, connecting to my phone and everything else I did not want, I found Altronics were still selling the original unit and duly ordered a new one. While waiting for the new unit, I could not leave the thought alone that it was a simple unit, the fault had to be in the beeper circuitry, and I could not allow myself to be defeated! So instead of tidying up my bench and sweeping the faulty unit into the bin, I had another look. Having eliminated all the likely components around the beeper circuit, I realised that the beeper had two sound levels that were controlled by a two-pole, three-position slide switch located on the other side of the board. The switch doubled as the on/off switch and was connected to the beeper circuit by two tracks that meandered across the board, avoiding other tracks and components. Testing the switch contacts, I quickly found that they were either open-circuit or had a high resistance. I bridged out the switch, and the beeper came to life! I decided that as we only ever used the unit on low volume, it was easier to leave the switch bridged than find a replacement. The on/off side of the switch seemed to be working fine. With 20/20 hindsight, I realised that in circuits such as these where there is little loading of parts, and barring a random component failure, the most likely component to fail is the one subject to mechanical wear. So I probably should have looked at the switch first. The unit was returned to service, and I now have a brand new unit sitting on my shelf as a backup! SC Nigel Dudley, Ocean Beach, WA. Australia's electronics magazine May 2026  103