Fixed the bass subwoofer!

This is just another example of messing with something in a different way leading to an unexpected solution. I've been trying to remember what the last thing was that I fixed in this manner - while messing with something in a different way that I probably would not think of right away leading to the solution of fixing it. But today lead to fixing the subwoofer for the Dolby sound system, which hasn't worked in 10 years since we moved out of the house on Euclid.

When Mom lost the house due to foreclosure 10 years ago, we packed up everything and minimally unpacked some things at my grandparents' house. One of the things that did not get set up was the Dolby sound system. It wasn't until when we moved in where we ended up did that get pulled out - and in fact I had to look for the subwoofer because I forgot which box it was in.

When I brought it down, it still powered on but the speaker wasn't doing anything. Not knowing what the problem was, it just sat unplugged and unused. Which was a shame since Mom spent so much on the speakers, bought at Circuit City.

Thankfully, instead of tossing it out like so many others would have, we left it sit where I put it. Eventually it would get fixed or replaced, right? And in all this time, I kept bringing up the idea that I would at least try to figure out what the problem was, but due to lack of energy, I wouldn't touch it for a while. Life just went on around it. Things got piled on it from time to time. This thing sounded GREAT when it worked back in town. It's a shame it stopped working. Or did it?

It would power up, light up the LEDs on the back (for Off or On), but the speaker would do nothing. Not like it's supposed to - a nice big loud Thump when turned on. So it's getting power but why not the speaker?

Today I finally decided I had enough of this nonsense and opened it for the 3rd time (must be anyway) looking for obvious signs of component failure. No leaking capacitors. No burst or burnt transistors - I don't even have a tool to test those components. I looked it over and couldn't find anything. I tested the speaker, and it did make a noise as I checked the impeding resistance (aka impedance) and even registered a value. OK, so why isn't it working?

I checked where the connector for the subwoofer went into the 2nd board (the power board presumably) and saw where some of the circuit traces went. I couldn't tell a thing. It wasn't until I was putting it back together out of defeat that I decided - Hmm, maybe the relay that turns it on in Auto mode isn't doing enough to connect? Thinking of something my dad would have done, I got out a wood back scratcher, and while turning on the subwoofer from Off, began tapping it, and that's when the speaker started to suddenly show some signs of doing something. Hmmm....! 

So further tapping and slight pressing on the power board started to yield interesting results. There was a solder connection that somehow went a bit out of spec to the point where it should be visible and a simple connection somewhere just needs a little heat and solder to make it work again. I found one spot that looked like it needed it, but still didn't have it nailed down yet. Some more tapping with a chopstick brought me closer to the immediate local area where somehow the solder connection just didn't work anymore, gave them all decent heat and a touch more solder, and tested it.

Turn on and THUMP! The speaker is working again!! HOLY CRAP. Was this the problem? A slightly less than decent soldering job that went out of spec by an invisible micrometer? The tapping helped me find the part of the circuit board where the problem was, and careful precise probing (shut up) helped me localize more of the solder points that needed touched up. I tried looking at solder points that just didn't look right, and eventually got them, hopefully all of them.

It's a big difference between what I had been hearing and what I can get out of my DVDs now.
And I saved a LOT OF MONEY being able to fix it myself.