Hello all !
Before I start, I am pretty much a newbie in electronics, I know a few basics, the simple things (Power/Voltage/Intensity/Resistance), and can just about identify resistors, transistors, capacitors and LED bridges (and that probably covers it !). Here goes the problem:
Symptoms
- When I switch the subwoofer on, from "cold" (transformer and capacitors unloaded), a big power jolt is sent through the 10" speaker. (see Video 1)
- Now, the interesting thing is, once the source is constant (film playing in DTS for example), the sub behaves normally. If, however, I pause (amp returns to Stereo/PCM default mode) and resume the film, another huge jolt is noticed.
- Similarly, when I switch from one channel to another, on the amp, an identical jolt is noticed each time. (see Video 2)
Video 1 : YouTube - Subwoofer amp problem 1/2
Video 2 : YouTube - Subwoofer amp problem 2/2
A few notes
- As far as I can tell, the audio source is not the issue : I've tried using a walkman as sound output, into the sub, and a few other things. The fact the jolt happens when the sub is not connected to any audio source (from a cold switch on) also tends to confirm that.
- The electricity supply in the house is fully earthed and matches expectations
- Importantly : this never used to happen, I know this comes from a mistake I made. I shorted something while the sub was on, having dropped a bit of foil inside the sub (silly, I know). I suspect what I shorted was the output wires (black and red) to the speaker, afterhand having noticed the wire connections were bare (from the connectors to the speaker core)
I have been doing a fair bit of reading, and have started by testing the two biggest transitors, the NPN and PNP transistors most obvious on the pics/videos. Both were fine (I followed a tutorial) apparently. Could it simply be a capacitor discharging each time, due to something else malfunctioning? Or, could it be a capacitor that is simply not doing its job anymore, and the jolt coming directly from the transformer?
I'd love to here your thoughts on this. And beyond repairing this subwoofer, i would love to use this as an opportunity to acquire some basic electronics skills and learn from this, the amp and board being pretty simple overall (it would seem!). I have a multimeter and soldering iron ready for action!
Any advice would be much appreciated
Tony
Before I start, I am pretty much a newbie in electronics, I know a few basics, the simple things (Power/Voltage/Intensity/Resistance), and can just about identify resistors, transistors, capacitors and LED bridges (and that probably covers it !). Here goes the problem:
Symptoms
- When I switch the subwoofer on, from "cold" (transformer and capacitors unloaded), a big power jolt is sent through the 10" speaker. (see Video 1)
- Now, the interesting thing is, once the source is constant (film playing in DTS for example), the sub behaves normally. If, however, I pause (amp returns to Stereo/PCM default mode) and resume the film, another huge jolt is noticed.
- Similarly, when I switch from one channel to another, on the amp, an identical jolt is noticed each time. (see Video 2)
Video 1 : YouTube - Subwoofer amp problem 1/2
Video 2 : YouTube - Subwoofer amp problem 2/2
A few notes
- As far as I can tell, the audio source is not the issue : I've tried using a walkman as sound output, into the sub, and a few other things. The fact the jolt happens when the sub is not connected to any audio source (from a cold switch on) also tends to confirm that.
- The electricity supply in the house is fully earthed and matches expectations
- Importantly : this never used to happen, I know this comes from a mistake I made. I shorted something while the sub was on, having dropped a bit of foil inside the sub (silly, I know). I suspect what I shorted was the output wires (black and red) to the speaker, afterhand having noticed the wire connections were bare (from the connectors to the speaker core)
I have been doing a fair bit of reading, and have started by testing the two biggest transitors, the NPN and PNP transistors most obvious on the pics/videos. Both were fine (I followed a tutorial) apparently. Could it simply be a capacitor discharging each time, due to something else malfunctioning? Or, could it be a capacitor that is simply not doing its job anymore, and the jolt coming directly from the transformer?
I'd love to here your thoughts on this. And beyond repairing this subwoofer, i would love to use this as an opportunity to acquire some basic electronics skills and learn from this, the amp and board being pretty simple overall (it would seem!). I have a multimeter and soldering iron ready for action!
Any advice would be much appreciated
Tony