Noisy audio

[Gearhead]

Hi. I posted this in the Electronics section, only got one response (thanks RPG). I was wondering (hoping) if maybe it didn't get seen over there and there is more input to be had.

 

I have a noisy audio system. It's happens on all sources (radio, tape, intercom, CB) and is detectable in the speakers but worse in the headsets. It appears to be a noisy power issue. It changes pitch with RPM, and here is the thing I find strange: it decreases when the bike had additional electrical load. Brakes or driving lights cause it to go quieter, and the blinkers do just what you might expect, the noise gets quieter-then-louder...etc.

 

I figure I'll check the ground on the system, as well as the ground on the factory noise filter. Do noise filters go bad? Any other ideas?

 

Thanks,

Jeremy

[GeorgeS]

I have the same thing on my 89. When bike was new, there was no ignition noise in the Radio, tape, or intercomsystem. For the last 3 years its seems to be getting worse.

 

Basicly a Noise filter for 12 circuits is just a Big Big Capacitor. ( usually 1000 to 3000 uF unit )

 

Rule of thumb, is the larger the amount of capacitance the better.

 

Or, commercially built units: Check this web site for examples. http://www.tessco.com/products/displayProducts.do?groupId=619&subgroupId=65

 

Also: Search Google: " MSD Noise Filter. $37.95" " Automobile ignition noise filter "

 

You will find a lot of information by searching this google search words.

 

I will do some more checking into this, as I have to do something to mine also. Will let you know what I find

[GeorgeS]

Radio shack has Capacitor p/n 272-1022, 4700uf 35V

caps for $5.49. Add one or two of these just before the Existing Noise filter.

 

Also, Radio Shack p/n 272-1047 1000 uf 50V for $1.69 each. I am thinking adding one of these to ground just at the Power Input, to the CB control panel, The Radio control Panel, and the power plug into the tape player.

 

Also, the 6 wire cable, that runs back to the passenger control unit, might be picking up Ignition Noise.

The R/B and R wires carry power. I'm thinking a 1000 uf cap added to the R/B wire back at the pas control might help. ( worth a try )

 

See, page 8-42 Schematic of service manual for wireing showing pull apart plugs, and Wire Color Codes.

 

This also shows that the Noise filter, the Amp unit, and the Tuner, seem to have a Case Ground wire running to a Ground stud someplace. Black wire's going to ground. Make sure these grounds are Zero ohms to ground. I have not checked these myself, but will look into it.

 

Hope this helps.

 

If anybody, has any luck with this information, please let me know.

[Gearhead]

Hey George,

 

Yeah, I've been looking at those schematics, too. I was hoping that one of those cable routing diagrams in the back of the manual would have ground points, but alas, they do not, so I have to go ground-searching.

 

When adding a cap in the circuit, do you just tap in to the power wire and go thru the cap to ground?

 

According to the schematic in the manual (p. 7-3 in the 86+ manual), the factory noise suppressor has the power wire go thru an inductor of some sort, then splits - one leg goes to the radio, the other leg thru the cap to ground.

 

Jeremy

[Condor]

I'd check the charging circutry. I'm thinking that if the noise quiets down when an increased load it put on the system that it might be stator or rectifier related. Possibly a ground wire that's worn thru and the current is using the frame to complete the circut??? Or the antenna shield is shorted to the frame somewhere. Years ago we used to get a lot of plug popping or alternator whine in the CB's and an inline frequency choke in the power leads usually cured the problem.??

[GeorgeS]

They all help. Choke, or Capacitor.

Rule of thumb is the closer to the Source of the noise you put the Cap, or Choke the better.

 

That link I posted had many different commercial noise filters. Cheap to expensive.

 

the basic capacitor is just from 12 V line to Ground. Idea is the Cap, pass's AC ( any varying voltage ) to Ground, but does not pass DC.

 

A Choke, or in line inductance, Will pass DC, but block AC, ( your noise is AC )

 

So some of those commercial filters, will be a combination, of Inductance, and capacitance.

 

I was checking mine today, on a short ride, seemed to be a lot of noise just on the Intercom, with NO microphone pluged in. This has been getting worse.

[rewindgy]

J & M used to sell one that plugged directly in between the stator output leads and the regulator. It stopped everything! Rumor is Rivco may still have some??? Also try Sierra Electronics as they may have an option.

[Gearhead]

I'm also posting this in a similar thread in the electronics tech section.

 

I eliminated about 90% of my noise, and it did end up being ground-related. I am optimizing the alternator output by minimizing the losses. I followed a troubleshooting chart on Electrex's web site, very thorough, I recommend it. One test was for voltage drop from the regulator to the battery, both on the hot and ground sides. In my case, both at idle were around .15-.2V. But when I turned on the driving lights and revved up the enigne (increasing the load and output) the drop was .6V hot and .4V ground. I ran a 12 ga wire, soldered into the regulator ground wires on the regulator side of the connector, up to the neg side of the battery. This takes some of the current and reduces the voltage drop to near zero. It also eliminated most of my noise!

 

Now there's just a small bit of that same noise that's not volume-knob-related, and also a component of noise that does increase with volume, but it only comes on radio and sounds like ignition interference.

 

Does anybody know where on the 1st gens the ground harness attaches to the frame?

 

Jeremy