Sound Fault in a Toshiba Equium A100 Laptop
This old laptop was working well until the sound from the right speaker disappeared. If it was possible to repair it economically, it would be preferable to scrapping it and buying a new laptop, since it otherwise did everything required.
As any computer technician will tell you, when a fault occurs in laptop speaker output, the culprit is usually the headphone jack socket failing to maintain the proper speaker/headphone contacts. However, on checking by plugging in headphones, it was found that there was no sound in the right channel here either. This looked a more interesting problem.
Picture 1 shows the speaker connectors on the System Board, accessed by removing the keyboard.
Injecting a tone signal here showed that both speakers were working fine. The next step required the laptop top cover to be removed so the required audio components on the System Board could be accessed. Luckily, on this laptop, all the main audio components are on the top side of the System Board, so it was not necessary to remove it from the base for diagnosis.
Picture 2 shows the Audio Chip (U14 a Realtek ALC861) and the Audio Amplifier Chip (U18 a Maxim Max9750) and the Volume Control.
Picture 3 shows the circuit diagram of the Audio Amplifier components. The Speakers are fed from the Amplifier OUTL and OUTR ports, signals SPK_OUT_L and SPK_OUT_R.
Applying the test tone at these points gave sound out of both speakers. Next we check the inputs to the Amplifier at INL and INR ports with the test tone, again getting sound from both speakers, confirming the amplifier is working.
Now we must test the other side of the 2.2uF capacitors C289 and C290. Picture 4 shows the Amplifier and the Capacitors C289 and C290.
We find that applying the test tone to these points gave sound out the left speaker but not the right speaker. Removing C290 and testing it with a capacitor tester showed it to be open circuit. Fault found!
Replacing tiny components such as this faulty capacitor, in an area having many other components is very difficult to do with a regular soldering iron. I use a basic hot air rework-station, which makes the job very easy. To remove the component, just heat it up using about 300 degs C air, and after a short time lift it off the board with tweezers. To solder the new capacitor in place, I find it very easy using Solder Paste and the hot air Gun. Dab a small amount of solder paste on each of the System Board pads of the capacitor, place the capacitor on the pads, and simply heat up the capacitor until the solder paste melts and completes a high quality solder joint. Job done – right speaker now working fine.
A few words on the tools I used, because using the right tools will make a difficult job a much easier and quicker job.
The simplest one will do to check voltages and continuity.
As in this case, it can be difficult to use a Multimeter to conclusively demonstrate that a faulty capacitor is open circuit, so to be sure, a capacitor tester is needed. However, no need for great expense here – I use a DM6013.
I use an old and simple Nombrex Signal Generator to generate a 1 KHz signal with sufficient amplitude to drive laptop speaker directly. A Tone Generator is essential for audio fault-finding. If you do not have one and cannot find one to suit your budget, download a software Tone Generator onto another computer which can then output the tone from its headphone socket to the laptop under test. Get it from:
Manufacture a cable using a computer stereo jack plug on one end and pair of small cheap probes on the other to inject the tone from the headphone socket into the desired place in the circuit.
Hot Air Rework Station
I use an Atten 858D, which works beautifully and did not cost a great deal – see eBay prices – around £30 UK.
I use solder paste now almost exclusively, even with a soldering iron. It produces, with high reliability, neat and electrically sound joints. Never known a dry joint with it yet. Get it in syringes for easy use, but more economically in pots. Apply to pads with a dental pick! Because of confused terminology in eBay (and other) sales forums, be sure you are getting Solder Paste (i.e. a mixture of solder and flux) and not just flux.
This article was prepared by Gerry Millward from the UK. He is 73 years old and is retired from his career as an electronics engineer (with a strong bias towards computing) in the UK Aerospace and Defence industries, and the RAF. He worked on his first computer (an AEI 1010) in 1960 as an AEI apprentice, and wrote his first computer program in Elliot Autocode on an Elliott 803 computer in 1967. He is a Chartered Engineer and MIET. To keep himself constructively occupied, he is now a self-employed computer technician in a village near Bristol in the South-West of England. Relearning the old skills of soldering using traditional and new tools, after so many years, was a great challenge!
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S- If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
P.S.S– If you are a beginner and wish to learn laptop repair you can check out the link HERE or click on the image below: