Elec. Prob.

RoninLB · 05-01-2003, 05:47 AM

I did a quick install of a MSD, MSD coil, and MSD tach adapter.. I bypassed all stock wiring, except tach feed wire. The stock external voltage regulator was disconnected on a previous alt. install. So now the "Radio [interference] suppressor" seems to be non functioning because I'm getting radio speaker ticking.

Porsche Workshop manual elec. diag doesn't show the interference suppressor. I also looked in the specific diagrams at the rear of the full diagrams, no luck. The plug into the suppressor is a 3 pin with Blue, Brown, and Black.. the sheathed wires out to another plug is Red/Blue, Brown, and Black.

So I may have to dig into the temporary birds nest of the MSD install.. another "fix" is doable until I install new resistor spark plugs with future carbs.. the plugs now are new. The good stock plug wires are still in.. I'll probably do Magnecore later today..

so, does anyone have any idea how to reinstall this interference suppressor or how it's wired.. the pic is for a '75. number 8 is the suppressor

Superman · 05-01-2003, 06:54 AM

Sure wish I could help, Ron. Fortunately, just a little patience is all you will need. There are folks here who regularly provide about twice as much electrical information as I can even understand. Good luck.

Rot 911 · 05-01-2003, 07:10 AM

Do you want it stock or just get rid of the ticking? If you want to get rid of the ticking just go to Radio Shack and get a suppressor from them and wire it into the hot lead to your radio.

RoninLB · 05-01-2003, 07:15 AM

Radio Shack was on my mind.. I don't care if I fix the stock supperssor to much.. I just don't like a stock problem I can't fix.. and then to not find any wiring on it pissed me off..........Ron

Early_S_Man · 12:52 PM

Ron,

That stock suppressor only addresses RFI noise produced by the slip rings and regulator ... even if you did hook it to the internal VR ... I doubt that it would help with the noise from the MSD unit!

An old condenser for a distriutor would work if connected as close as possible to the MSD unit on the power lead ... between the hot lead and ground -- this is known as a 'bypass capacitor' since it provides a low-impedance path for high-frequency RFI noise to be shunted to ground!

If that does not entirely cure the noise ... an inductor feed-thru noise suppressor inline with the radio power lead may help ... from Radio Shack! In extreme cases ... you can also install bypass capacitors on both sides of the inductor to form a low-pass 'Pi' filter for the radio/audio power lead. Disc ceramic capacitors of 0.1 mFd to 0.05 mFd at 200 Volts (or higher) would be suitable.

RoninLB · 05-01-2003, 10:19 AM

great Warren.. now I have another mission..........Ron

Superman · 05-01-2003, 12:35 PM

See? There he goes again. Warren just gave you advice that I cannot understand. I guess I'll stick to labor relations.

Early_S_Man · 05-01-2003, 12:51 PM

Super Jim,

Since you seem to like 'specific' details ... I edited the recommendation with a bit more explanation and details!

MotoSook · 05-01-2003, 01:04 PM

Good grief Warren! I'm with Super on this one..what the heck are you talking about

I think I just lost a few brain cells and my head hurts now

That's a great post.

RoninLB · 05-01-2003, 01:17 PM

Quote:

Originally posted by Superman

Warren just gave you advice that I cannot understand.

can't beat a big education in 2 little sentences.. the trackdown now becomes doable.. So Jim, maybe working for a living is a distraction, LOL..........Ron

RoninLB · 05-01-2003, 01:33 PM

Quote:

Originally posted by Early_S_Man
Ron,

... a 'bypass capacitor' since it provides a low-impedance path for high-frequency RFI noise to be shunted to ground!
...bypass capacitors on both sides of the inductor to form a low-pass 'Pi' filter

Yes Warren, it's definately high frequency..

And both sides of the inductor.. ground loops is somewhat understood, but I can't understand both sides of the inductor

..........Ron

Garyo4 · 05-01-2003, 01:38 PM

Warren, WOW, makes a newbie like myself spin with mental overload........I am humbled

Superman · 05-01-2003, 01:41 PM

I just wish I knew half the stuff Warren has forgotten about electrons.

bell · bell's Garage

yes warren is on the right track, and i actually understood everything he said

ron you have an amp on your focals/tweets correct? try adding a wire from the ground shield on the rca at either the amp or the radio and connecting it to ground (this will ground the shield of the rca) alot of times this will isolate the ripple which causes noise, then try radio shack

RoninLB · 05-07-2003, 11:26 AM

BINGO...

did a quick run to the store to get an old chevy points condensor and, and an inline radio suppressor. NG/NG

did an e-mail to Aircraft Spruce for 2 specific in-line noise supressor that Warren suggested.. they have many suppressors but wrote back NG

tried resistor spark plugs, worked a little bit, 1/2 NG

tried bells suggestion on grounding audio feed wire sheath, worked a little bit, 1/2 NG

from frustrated energy I start reading the MSD big full line catalog and big "Wiring Diagrams & Tech Notes"[$5]

bingo.. no more radio speaker noise w/MSD noise suppressor used alone.. I'm in the middle of wrench work and this job had to be cleared up to clear me up........Ron

bell · bell's Garage