87 VR rider's headset level adjustment

[Gearhead]

Hi,

 

My 87 VR has had a problem with the rider's headset level adjustment (on the left handlebar). Symptoms:

• When turned all the way up it sounds fine. I would just use this setting, but it has more engine whine that way.
  
• As I turn it down notch by notch, the left speaker goes down more than the right, so it sounds like the music is shifting to the right. The second-highest notch (with the big dot) still sounds good in this regard; the shift is small at that point.
  
• Sometimes the sound starts breaking up, like a slightly bad cell phone connection. This is exacerbated by bumps or rough pavement. It never cuts out completely. Again, this does not apply to the max level.
  
• Wiggling the attenuator knob does not affect either symptom.
  
• Only applies to rider's headset. Passenger's has none of these symptoms. Dash speakers work fine.
  

I don't really understand how these attenuators work. I thought of it as a variable resistor, but that doesn't make sense because if you unplug the attenuator line where it ties into the headset line, the level goes to max. I thought the level would go to zero with a broken circuit. At any rate, I've cleaned that connection and the attenator knob. Clearly something is loose due to the "bump" behavior.

 

Help! Ideas? Anybody seen this before? Is the problem in the knob or its box and circuit card, or in the cable somewhere?

 

Thanks,

Jeremy

[Gearhead]

Nobody's had this before?? I feel like such an oddball. :-(

 

Jeremy

[utadventure]

I had a similar problem with the passenger system. I replaced the cable from the amp to the rear passenger point under the seat and solved most of the issues. I had more success after replacing the cable that the passenger plugged into.

 

Dave

[mbrood]

It's probably a simple two section (ganged) potentiometer (pot, variable resistor) and one side is funky... Probably any radio repair shop can replace it with another of the same value.

[Bob Myers]

Or you can buy tuner cleaner at radio shack, take the knob off and spray it very heavily into the hole, then replace the knob and run it through its range of motion several times. If that helps then do it again to get it all. Or you could take the box apart and get right to the pots. They're just dirty, they don't attenuate enough current to cause them to burn out.

[Gearhead]

I found the problem. Well, that's not quite true. I fixed the problem. First, thanks you guys, esp. Mike Brood who sent me a PM with helpful info. The pot shunts the signal to ground, so the lower the resistance the lower the volume because more gets shunted. There are 3 wires in the attenuator circuit - left, right, and the common ground. Then I consulted the manual and there is actually some pretty detailed info on checking the resistance on the two channels of the pot at different knob settings.

 

I didn't find any problem with the pot as measured at the first connector behind the headlight. Cleaned that up, greased and reconnected. Then I made measurements at the next connection where it ties into the headset cable to the left of the battery. Didn't find anything difinitive there either. A couple readings were a little wonky, but I wasn't sure I had the meter probes making good contact. In the end, all I did was clean and grease both of those connectors and tug on the cables and now the level knob works great!

 

Jeremy