My PC speakers have a hum. They hum when disconnected from the PC. They hum when I take them into another room with power only connected. They hum when I use a different power supply. I opened the one with the pc board and looked it over and saw nothing out of the ordinary. I cleaned it with IPA and they still hum. I used a can of duster turned upside down and froze each individual component and they still hum. They are old but they have great sound. I would really like to repair them if possible. If anyone can give me so help, I would appreciate it. I have no idea where to start from here.
Thanks!
What brand or model speakers are we looking at?
Radios + Tubes + Scopes + Cars= Nothing better!
Labtec Model 80311ST
Nothing comes up for that specific model. I have plenty of memories going through elementary school, they had a bunch of this brand speakers, those were the days. Being of that age, I would guess any electrolytic caps are past their days of use. Might be worth checking those if any are present. I wouldn’t expect 60hz hum from something with a SMPS adapter but you did try multiple supplies. Other than that it would be difficult to pinpoint without having them in front of me.
Radios + Tubes + Scopes + Cars= Nothing better!
@ballsar-frozenoff The question is: Have you owned them from new and do you remember them working properly before (as in) did they ever worked with no hum at all ?. Anyways the most common problem to any amplified sneaker would be the power supply smoothing (filtering caps) and the second would be the poor coaxial cable that is attached to the audio jack. Very often that coax cable breaks inside especially near the jack. Another question: does the speakers have a volume control potentiometer ? If so when moving the pot toward the minim (zero volume) position does the hum still persists just as strong ? You can also try to see if the hum is still present after resoldering the audio coax cable from the electronics board. Another defect could be in relation with the volume pot itself. Try testing the pot with an ohm-meter and see if the cursor runs smoothly while looking at the ohm-meter (as it should). Also try testing all electrolytic caps as well. It could also be a bad) soldering point located at any component on the electronics board . Any combination of the above is also possible. Good luck.
I have owned them since new. They are approximately 30 years old. I have used them on various PCs I have built and owned over those years. As far as the cable is concerned, the hum is present when the cable is disconnected. I moved the speakers into another room and powered them on with nothing but the power cable attached and the hum is present. I tried different power supplies and the hum persists. The speakers do have a volume control. The hum increases and decreases with the volume. I will test the volume control and the caps as soon as I can. I bought a new pair to use until and if I can get these working. I am a retired IT manager and have spec’d many components and built dozens of PCs and at 30+ years old and they are still the best PC speakers I have ever owned or had experience with. I do appreciate the advice and I will certainly follow your suggestions as best as I can. Thanks very much!