What is this below the left faring pocket?

[lcdrjoe]

I was hooking up a radio in the 87 interstate and behind what would have been the radio (it's just a false cover now), there was the wires leading to the speakers and a couple blue wires that went down to below the left faring pocket. I removed that pocket by removing the four screws. Below that pocket there's a bunch of stuff including a small box that those blue wires lead to. The blue wires were connected to a black wire and a yellow wire, then to a small box about half the size of a pack of cigarettes, with the same color wires coming out the other end. I'll attach a pic if I can. Anyone know what that box does? I sorta figure it has something to do with the audio, but not really sure. There's also a couple fuses in there, a 3 amp and a 10 amp, along with a small pouch that has a spare of each. I was hoping that there would be spare key in that pouch. I did look at the schematics I could find and could not find a box that had a black and yellow wire going into it and coming out of it.

[Bike...and Dennis]

The box is aftermarket, I think.
The wiring and fuses are there to hook up an OEM radio system but can be used to power an aftermarket radio as well.

[lcdrjoe]

I think you're right. I pulled it out and I'm still not sure what it actually is supposed to do, but I'm attaching a pic of what's inside it. One of the yellow wires has 0.9 volts with the key on and it's not getting that 0.9 volts from either of those fuses in there, because I pulled them both out. I'll keep fiddling with that till I get it figured out. Thanks for the reply.

[Bike...and Dennis]

That's interesting. I have no idea what it is, but someone with an electronics background should be able to figure it out.
What doesn't work if you take the fuse out?

[WingAdmin]

That's not an amplifier. I looks like a noise filtering circuit, probably trying to filter noise from a power line?

[Premtech]

It looks like a simple crossover circuit for your speakers, bass and tweeters. Would like to see the foil side of the circuit to confirm that. But the audio signal from the radio would clearly be a low voltage, confirming the .9 volts you see on the meter and the transformer or coil is responsible for the low pass, while the cap produces the high pass necessary for the tweeter range. A crossover splits the audio signal into two or three different signals (sometimes more, depending on how many different drivers a speaker system has), and sends the low frequency, or bass, signal to the woofer, the high frequency, or treble, signal to the tweeter and so on.

[ssquare]

Hello. I'm a retired electronics engineer. The box performs one of the following functions:
1. If the input and output wires were connected in series with the power lines to the radio system, it is acting as a common-mode filter to filter out noise from the electrical system that typically interferes with AM radios in vehicles. Depending on the technologies present in the bike, there may be significant noise present.
2. If the input and output were connected to the audio speaker lines, it could be a simple crossover network as another respondent commented. However, the wiring present would only support one channel. Both channels would need a crossover for proper operation. Therefore, you would find another of those boxes somewhere in the bike.

To me, it looks more like solution 1 above with the information you have provided.

By the way, if you need a spare key for your bike, I know an eBay seller of Honda keys that is reliable. I bought two spares for my GL1500 from him for $20. Let me know if you would like that information.

Good luck.
Steve

[lcrane]

I am going to have to agree with ssquare that this appears to be an in-line LC alternator noise filter designed to go in series with the power lead to a low current less than 5 amp piece of audio equipment. The fact that it has an onboard fuse is another possible indicator of this application. While examining the board look closely at the inductor or transformer looking part and check that it only has two leads connecting to the circuit board. The capacitor more than likely is 500-1000uF electrolytic type. It should not be wired in series with the speakers though. Hope you find this useful and good luck.

LC

[OldguyGlen]

plus 1 ++^ Looks like a noise filter in the power supply line to the radio. My bike could use one !!! My oem radio in my Vetters fairing buzzes pretty good on weak signal stations. But I never use the radio on the road... too distracting.

[lcdrjoe]

It's been a while since I could get on this site. I still don't know what that thing is, but I'm probably just going to pull it out and chunk it. I normally just listen to pandora on my earbuds when riding and I don't have any issue with noise. Thanks for all the ideas, I really appreciate all the expertise here. I'm posting a new issue though in a new thread.