[Bruce Meyer]

I have a 69 GTO that I just finished restoring. I put a CD player in the glove box. It works great when the car is not running. As soon as I start the car the stereo gets extremely distorted whether Im listening to a CD or Radio.
I did a search and saw some people had similar problems due to bad grounding. I tried everything including running a ground wire all the way to the battery. No difference.
Im stumped. Any ideas?

[Old Goat 67]

Give us your best explanation of distorted.

Goes with ignition or a whine?

[Bruce Meyer]

No whine that changes with RPM. The distortion sounds like someone turned a cheap radio all the way up except it does it as soon as the car is started at any volume.

[Old Goat 67]

What is happening to the voltage value on the 12 V lead? Is it going way high?

Sounds like something is going on with your alternator. Why don't you try disabling it with the belt or disconnecting all wiring to it to see what happens then.

If the odd actions go away, maybe a rebuild of the alt/reg or a 12V filter in series with the radio power lead would be in order.

Charles

[Bruce Meyer]

Thanks Charles. Im begining to think its the alternator too.

[Bruce Meyer]

Found the problem. I disconected the tach and the problem went away. I guess Im going to have to run a shielded wire for tach??!!

[Old Goat 67]

Factory tach or aftermarket?

Never heard of a tach causing that, but anything is possible. I'd try a filter capacitor on the B+ lead to it or the radio, but if it is RF being generated from it that wouldn't help.

What lead did you disconnect, B+ or signal?

[Bruce Meyer]

Factory tach. HEI distributor. Disconected the lead from distributor. Tried a filter cap on the stereo and that had no effect. I can live with no tach for now. I have some sheilded wire I can try when I get around to it.

[Old Goat 67]

Probably thousands of cars like yours, Mine Included.

I'm guessing something has happened inside your tach to generate a frequency that your radio reciever is picking up. Weird.

Sure would be neat to try hooking up another tach, just to see what would happen? Maybe the radio is at fault?

Charles

[Bruce Meyer]

The odd thing was it did it with the CD player too not just the radio. Something very weird.

[Old Goat 67]

Beginning to sound like a B+ noise then. Tape is just audio frequency.

[george kujanski]

You mentioned CDplayer and radio separately as if they are 2 separate units. If so, make sure the chassis of both are connected to the same ground and interconnecting cables such as the audio left and right are coax cables with the shields intact. The tach wire is going to have some higher frequencies on it but those don't normally get into the radio unless the radio chassis ground is poor or the tach ground is bad and getting to actual ground thru th radio/Cd chassis.

George

[Old Goat 67]

Good Thought.
These were grounded directly back then, but they are 40+ years old.

[Bruce Meyer]

No they are not seperate units. The Cd player has radio too. A bad ground on the tach could be the problem but the tach was working good before I installed the radio/cd player. If it had a bad ground it probably shouldnt work or at least read erratic.