This actually happened (and was resolved) a couple of weeks ago, but I wanted to live with my system for a while and make sure it was OK before reporting about it.
As some of you know, I was alpha-testing one of the prototype tuner modules. (Nice unit, by the way, you will all be very pleased with its performance when it becomes available.)
When I was working on the installation for the tuner module, everything seemed OK except for some apparent RF issues with my keyless-entry system (detailed
here).
But afterwards, I noticed some faint alternator whine that sounded like it was only present when I used the tuner. I spent a long time going back and forth with one of the Rio engineers trying to determine if it was a fault in the tuner's design. I couldn't find any fault in my system, and we tried several different ways to remove the noise to no avail. And the more I worked on it, the worse things became-- eventually, the noise crept back into the MP3-playback as well. So it didn't appear to be caused by the tuner module specifically, but I couldn't find what was wrong with my installation, either.
Since I was about to start my vacation, which involved a couple of long driving trips, I became determined to solve the problem, so that I was not resigned to listening to my alternator on the trips. I spent an evening ripping out all the wiring and checking every single connection and ground point.
When I found the problem, I was amazed at my own incompetence. The fault was, in fact, in my wiring. It was one of those places where I was absolutely certain that nothing could have been wrong. The only reason I even looked in this place is because I had already exhausted all the other possibilities. (I think there's a Sherlock Holmes quote in there somewhere.
)
Anyway, it turned out to be a faulty solder joint. It was on the wire that connected the main constant power line to the amplifiers. In my installation, this wire also feeds the Empeg's main power as well. This wire had a heavy-duty Radio Shack noise filter on it, and it was at the connection to this filter that the solder joint was faulty.
When I transferred the Mark1 from my Volkswagen to my Honda, most of the installation wiring came along for the ride. And when I replaced the Mark1 with a Mark2, I didn't change much. So this particular solder joint stayed pretty much untouched between two cars and two empegs.
The problem was that I'd relied upon the solder itself, not the wires, to do the job. I had been in a cramped position under the dash near the firewall doing the soldering, and had taken a short-cut. I had tinned both wire ends, then simply held the wires next to each other and flowed the solder over the two ends. This resulted in what seemed to be a nice solid connection. But after a while, it began to crack under strain and became an intermittent connection, barely holding itself together. When I removed the insulation and pulled on the wire to check its connection, it fell apart in my hand.
The crazy thing is that the system still worked like this, it just had alternator whine while it did. I'm not totally clear on how the power was getting from the battery to the amplifiers, but I know it had to be somewhere through the signal path. I think I had what might be considered a "reverse" ground loop. Some of the primary power reaching the amps was getting there via the signal wires. Perhaps some of it was coming through the ignition wire, I don't know for sure.
So I ripped out that whole section of wire and re-did everything. This time, instead of half-assing the connections, I made sure that the wire strands were completetely intertwined with each other before soldering.
Now everything is fine and working great. No noise any more.
The moral(s) of the story:
- When you have ground loop noise or alternator whine, re-check every single wire and connection point, no matter how sure you are that they're fine. Look in all the places you thought you didn't need to look.
- Don't assume that because it sounds like a ground loop, it involves the ground wires. The problem could be in the positive power wires, too. Power wires are the same as ground wires, the electrons are just flowing a different direction.
- When soldering wires together, don't trust the solder alone to do the conducting, or to be the structural integrity of the connection. The wires themselves need to be connected well before you start flowing the solder.
I'm going to link this in the installation problems FAQ in hopes that it might help some other poor soul.
___________
Tony Fabris
Previous Topic
Index