External Computer Speakers - Page 1
Forum section: electronics / repair

author: chipwitch
author_rank: Frequent Contributor
timestamp: September 03, 2020, 03:50:35 pm
content: Hi All!! Been a minute! Moved out of state. Been a couple years getting settled. I'm still not quite there, but beginning to get back to having a little fun now and then.I have some external computer speakers that I really liked when I got them, but suddenly, for no apparent reason, they stopped working. Seems others have had similar problems with these as well. I wanted to see if any of you experts might have some suggestions for me, a perpetual noob.The speakers are Creative Labs T20 Series II. They have a head phone jack that works, so I know my audio setup works getting the signal to the speakers. I understand that some of these speakers have energy saving circuitry to go to sleep when there is no input, so I made sure that all audio input was as loud as my device would go. It has been tested on 2 desktops, 1 laptop and a smart phone. OS: Windows 7, 10, Linux and Android. The speakers have been tried with and without the dependent speaker connected.I've opened the cabinet of the primary speaker. I could not see anything obvious. No swollen caps, oozing or obvious heat issues. The only interesting observation that I think might be a clue to y'all is that the speakers work for about a half second when you unplug the power adapter. As if the caps are bleeding off voltage.I know it's a longshot, but I was hoping someone here might have a suggestion that I could try.

author: Mikey5791
author_rank: Contributor
timestamp: September 04, 2020, 03:14:36 am
content: Hi,You mentioned about external speakers "stopped working"....is it meaning the led power on not lit. When is the last time the speakers are in good working condition?Maybe It is time to check your power supply side. Could be failed electrolytic capacitor or bad solder joints. First step I will recommend you to check esr on all the electrolytic caps eventhough they are not bulging or show any symptom. Probably better to unsolder those larger capacity caps (over 500uf type) and use an esr meter to test. Otherwise, just recap all the major caps. Then we see how to proceed to next step.

author: bob91343
author_rank: Super Contributor
timestamp: September 04, 2020, 05:59:49 am
content: There are no secrets here. You would be advised to use standard troubleshooting practice to discover the reason for no operation.Apparently there are electronics circuits in the boxes that aren't working as they once did. So something has failed, either as simple as a wire breaking or as unpleasant as a burned out chip or transformer.You need to get a diagram or perhaps reverse engineer it so as to see what you have and decide how to proceed.Take some pictures. Google for a circuit diagram. We will help where we can.

author: Grandchuck
author_rank: Super Contributor
timestamp: September 04, 2020, 01:14:45 pm
content: Do you have an adjustable bench power supply? The reason I ask is that the speakers work for an instant at power down. It would be interesting to see if they work at reduce voltage.A schematic would help a lot! The auto power off perhaps could be easily eliminated (defeated) if that is the culprit.

author: chipwitch
author_rank: Frequent Contributor
timestamp: September 04, 2020, 02:00:37 pm
content: That would be interesting. My power supply only goes to 12v. The speaker requires 27vdc. Seems like an odd voltage to me.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 04, 2020, 03:58:53 pm
content: If the speakers work momentarily as you unplug the power supply, that could indicate a problem with a mute circuit.If the amps are single chip devices, they may have mute and perhaps standy pins that may not be being driven properly.e.g.https://www.st.com/en/audio-ics/tda7293.htmlMute circuit problems are surprisingly common on powered speakers.

author: chipwitch
author_rank: Frequent Contributor
timestamp: September 04, 2020, 05:33:18 pm
content: Quote from: Audiorepair on September 04, 2020, 03:58:53 pmYou may be onto something. Keep in mind I'm very much a beginner, so forgive me if I'm straying....If I can identify the amp chips (there's a chip I suspect but couldn't see any identifiable markings without a microscope) and find their schematics, I might be able to just ground out the standby and mute chips? This is kind a what I was thinking too. It just didn't occur to me that the mute and standby would just be a pin! So any discreet component failure that might get stuck sending a signal to the pin would mute it. I'll have to see if I can identify the chip. Thanks! I'll take another look tomorrow and report back.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: September 04, 2020, 08:50:20 pm
content: You might find, like me, the datasheets a little confusing."Standby On voltage threshold", for instance.Does this mean Standby is On, or the amp is On?You have a choice of grounding the Standby/Mute pins or leaving them open circuit if you want to disable these control voltages.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: September 05, 2020, 10:41:47 am
content: Some photos would help.