Radio Noise Suppression
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Success!
I FOUND THE CAUSE!
The source of noise is coming from the Accessory Power lead that's plugged into the fuse block. Odd thing though; even an RF Choke/Suppressor between that lead and the radio didn't eliminate the noise. I did what you guys suggested and ran a Power line directly from battery to radio (as well as Ground), and all is well. Will do like Blue1972 suggested and set up a relay circuit with a fused lead to the radio.
Honestly, I was ready to give up. It was really the last thing I hadn't done.
Much appreciate all the suggestions.
Steve
The source of noise is coming from the Accessory Power lead that's plugged into the fuse block. Odd thing though; even an RF Choke/Suppressor between that lead and the radio didn't eliminate the noise. I did what you guys suggested and ran a Power line directly from battery to radio (as well as Ground), and all is well. Will do like Blue1972 suggested and set up a relay circuit with a fused lead to the radio.
Honestly, I was ready to give up. It was really the last thing I hadn't done.
Much appreciate all the suggestions.
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Oh No!
Noise Returned!
Drove about 2 blocks, and the ignition noise returned. Totally cuts out audio and unlistenable.
See this icon?
Doesn't come close to what I feel right now. I am beginning to think there's perhaps a major flaw in the radio's design.
Steve
Drove about 2 blocks, and the ignition noise returned. Totally cuts out audio and unlistenable.
See this icon?
Doesn't come close to what I feel right now. I am beginning to think there's perhaps a major flaw in the radio's design.
Steve
Race Director
Joined: Oct 2008
Posts: 19,256
Likes: 1,678
From: Long Island
If you have points you may have a bad condenser in the distributor. Suggested by my friends father who is 85... (heli's don't)
I would also double check the antenna ground, sometimes the plate gets rusty and no contact to the antenna.
Just some suggestions that may also help.
I used the Freezer Tin Foil and grounded it , just because it was heavier and did not rip easy.
I also have the tin foil in my 72 and it stopped the buz.. ( but it has the full shields)
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Doesn't sound crazy at all. It's the sharp, snap-like interference that's coming over the speakers, and I believe it is distributor related.
Thanks for the idea.
Steve
Race Director
Joined: Oct 2008
Posts: 19,256
Likes: 1,678
From: Long Island
From my day's as a kid in the Sunoco Station - cracked insulator / fouled plug. Burnt connector on the plug wire, burnt contacts in the cap, bad rotor or heavy carbon deposit in the dist. cap.
I'm a big fan of QUALITY di-electric grease on electrical connections.
Hope you find the issue, these things can drive you nuts..
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
A note to add:
The coax cable from the antenna to the radio now runs along the driver's door sill, then across underneath the dash, to the radio. It could be picking up RF there, as opposed to running from the radio, through the transmission tunnel, to the antenna. Will tryout that change next.
Steve
The coax cable from the antenna to the radio now runs along the driver's door sill, then across underneath the dash, to the radio. It could be picking up RF there, as opposed to running from the radio, through the transmission tunnel, to the antenna. Will tryout that change next.
Steve
Pro
Joined: Apr 2013
Posts: 535
Likes: 8
From: London Ontario
Steve, what ignition wires are you using? Your description is sounding more and more like ignition noise. The factory had its own issues unique to a non-metalic car. The sound is usually from a source of electrical arcing; either the alternator (or other motor), or, the ignition system. By its very nature the ignition system is an endless source of high voltage jumping arcs! Make sure you are using good quality resistor core wires and try to fit the shielding back on (it fits over my HEI with some tweaking). Another option would be stainless shielded wires (Accel and others) that are completely grounded.
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
My plug wires:
http://www.ebay.com/itm/9-5-MM-RED-STRAIGHT-SPARK-PLUG-WIRES-DISTRIBUTOR-HEI-CHEVY-BBC-SBC-SBF-302-350-/130906186730?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e7a9de3ea
Appreciate the ideas guys.
Steve
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Race Director
Joined: Oct 2008
Posts: 19,256
Likes: 1,678
From: Long Island
Thinking back to my early days, one thing is super important --make sure all the ground strips from the battery to the frame and the engine are clean and in place.
sometimes the basics are forgotten.. don't ask how I know. (like changing the headlight bulb instead of checking the plug?)
sometimes the basics are forgotten.. don't ask how I know.
(like changing the headlight bulb instead of checking the plug?)
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Thinking back to my early days, one thing is super important --make sure all the ground strips from the battery to the frame and the engine are clean and in place.
sometimes the basics are forgotten.. don't ask how I know. (like changing the headlight bulb instead of checking the plug?)
sometimes the basics are forgotten.. don't ask how I know.
(like changing the headlight bulb instead of checking the plug?)
Steve
P.S.: For Sale: One new '73-74 Corvette Oil Pressure Gauge. Never installed!
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Re-routed antenna coax cable away from door sill/under dash, to through the transmission tunnel, to radio. Crackling noise still there.
Installed a coax noise filter on the antenna cable. Crackling noise still there.
Of particular note: The noise is absent for the first 7-10 seconds of radio operation (with the engine running). After then does it start; intermittently slow at first, then increasing rate of crackling to the point of completely drowning out all radio/aux player audio.
Did the lights-out inspection of the engine compartment while noise was present: No arcing seen anywhere.
Power and Ground to radio's Battery Input Lead and Ground Lead is supplied directly from battery and has a noise filter on Positive Lead.
Radio's Accessory Input Lead is still powered through car's original harness lead (Yellow) and has no filter/choke on it. I remember swapping the filter to this lead from the Battery Input Lead with no change in noise presents (still there).
Will place a filter on a direct-from-battery lead to the Accesssory Input Lead next.
Steve
Installed a coax noise filter on the antenna cable. Crackling noise still there.
Of particular note: The noise is absent for the first 7-10 seconds of radio operation (with the engine running). After then does it start; intermittently slow at first, then increasing rate of crackling to the point of completely drowning out all radio/aux player audio.
Did the lights-out inspection of the engine compartment while noise was present: No arcing seen anywhere.
Power and Ground to radio's Battery Input Lead and Ground Lead is supplied directly from battery and has a noise filter on Positive Lead.
Radio's Accessory Input Lead is still powered through car's original harness lead (Yellow) and has no filter/choke on it. I remember swapping the filter to this lead from the Battery Input Lead with no change in noise presents (still there).
Will place a filter on a direct-from-battery lead to the Accesssory Input Lead next.
Steve
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
I have the best fix for your problem.....RADIO DELETE! I removed the radio, antenna, capacitors and that fixed that. What more do you need to hear than the sound of a V8?
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Race Director
Joined: Oct 2008
Posts: 19,256
Likes: 1,678
From: Long Island
Sorry to hear you are having so much trouble.
Two things I can think of that may be a cause. If the speakers are grounded to the body not feed back to the radio, or if the constant power feeds from the "memory and lighting" circuits may be dirty and back feeding.
You could wrap the distributor in tin foil as a test. Just ground the foil with a pair of clips.
When I did my friends car we ran all the feeds to the battery.
As a last resort I would stop by a high power stereo shop, they may have info on the receiver and what it may need.
Two things I can think of that may be a cause. If the speakers are grounded to the body not feed back to the radio, or if the constant power feeds from the "memory and lighting" circuits may be dirty and back feeding.
You could wrap the distributor in tin foil as a test. Just ground the foil with a pair of clips.
When I did my friends car we ran all the feeds to the battery.
As a last resort I would stop by a high power stereo shop, they may have info on the receiver and what it may need.
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Not Ignition Noise.
The reason I think this static is not related to ignition:
This morning I drove out of the driveway with static and then onto an Interstate on-ramp. It was elevated. As the car accelerated uphill, the static stopped and the radio was 5X5. As the road leveled out, the static started again.
I started pulling fuses, one by one, to see if the static was on any of these circuits. I pulled them all and the static never stopped. The RADIO fuse caused the radio to quit. So if I run another hot wire directly from the battery to this Accessory lead to the radio, THEN PULL THE RADIO FUSE, I WILL HAVE ELIMINATED THAT FUSED CIRCUIT.
That's my next move. Will report back soon.
Steve
This morning I drove out of the driveway with static and then onto an Interstate on-ramp. It was elevated. As the car accelerated uphill, the static stopped and the radio was 5X5. As the road leveled out, the static started again.
I started pulling fuses, one by one, to see if the static was on any of these circuits. I pulled them all and the static never stopped. The RADIO fuse caused the radio to quit. So if I run another hot wire directly from the battery to this Accessory lead to the radio, THEN PULL THE RADIO FUSE, I WILL HAVE ELIMINATED THAT FUSED CIRCUIT.
That's my next move. Will report back soon.
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Static still there.
Next step: I will put a condenser on the alternator. Once I find one!
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
The Solution
Placed my NOS Shielding Box over the distributor (didn't think it would fit before), and whadaya know; no more noise. That was it. Them GM engineers did that for a reason, and I ignored it.
Easy Mike: You are a good "reader"!
I'd like nothing more than to kill this thread for now, but hope it lives on to help others.
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
It's not "Over"
So, I mount the newly painted side pieces, cram the shield on, screw it down, turn on the engine, and the static is back! 
Removed the cover, duct taped the bare surfaces of the insides, place it back on, and there's still static.
I'm not lying: When I first placed the cover over the distributor (just resting on it), the static stopped.
This would be hilarious if it wasn't so time consuming and frustrating.
Steve
Removed the cover, duct taped the bare surfaces of the insides, place it back on, and there's still static.
I'm not lying: When I first placed the cover over the distributor (just resting on it), the static stopped.
This would be hilarious if it wasn't so time consuming and frustrating.Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Yes, I did Ali. Entire shielding of the Ignition Wiring and Distributor, and an in-line Noise Filter on the Radio Power Lead wire (IGNITION), NOT the Memory Power Lead wire.