Need HELP with alt whine - Page 10

Perry Babin · 28th November 2007, 05:35 PM

http://bcot1.com/images/rca/temporar...eldrepair.html

pityocamptes · 28th November 2007, 05:43 PM

So your saying that the no ohm value means I have an open ground? I checked the HU while in the dash. Should I have pulled it out? Thanks again.

Perry Babin · 28th November 2007, 05:54 PM

You should have approximately 0 ohms when you touch one lead to the RCA shield and the other lead to the case of the head unit.

You need to do this with all RCA cables disconnected from the head unit.

Set the meter to the lowest ohm range. Touch the leads together to make sure the meter is working properly. You should read 0 ohms when you touch the leads together.

pityocamptes · 28th November 2007, 06:16 PM

OK. I will double check again later.

I do remember connecting the rca shield to ground and the noise got even worse, but I only did it with one of the rca outputs.

Thanks.

**Oh, is this a common occurance? Why would HU manufacturers fuse the ground, and not just run a solid trace?

Also, my preamp outputs on the Jensen HU are about 6" wires straight out the back that end with an RCA plug. I noticed the pictures you had were a little different. Should I break the insulation and solder to the shield, or should I solder a line off the rca shield as you depict?

Perry Babin · 28th November 2007, 06:43 PM

Was the EQ still in the circuit when you grounded the RCAs?

Without fusible shield grounds, if the RCA cables contact the main power wire, the RCA cable will burn from one end of the vehicle to the other. It's a fire hazard. This used to be relatively common before the shields were fused. I see a lot of people who pull their amp but don't pull the main power fuse and don't tape up the power wire. While driving, the wires (RCA cables and power wire) slide around in the trunk. Eventually they make contact.

Don't cut the insulation. The connection is between the RCA patch cable connector and the case of the head unit.

pityocamptes · 28th November 2007, 06:46 PM

Quote:

Originally posted by Perry Babin
Was the EQ still in the circuit when you grounded the RCAs?

Without fusible shield grounds, if the RCA cables contact the main power wire, the RCA cable will burn from one end of the vehicle to the other. It's a fire hazard. This used to be relatively common before the shields were fused. I see a lot of people who pull their amp but don't pull the main power fuse and don't tape up the power wire. While driving, the wires (RCA cables and power wire) slide around in the trunk. Eventually they make contact.

Don't cut the insulation. The connection is between the RCA patch cable connector and the case of the head unit.

I don't remember if the EQ was still in the circuit. How would that make a difference? Thanks again!!!

Perry Babin · 28th November 2007, 07:03 PM

If the EQ was in the circuit and was defective, repairing/restoring the shield ground of the head unit could not stop the noise because a second defective component was in the audio chain.

pityocamptes · 29th November 2007, 02:13 AM

Hi. I checked the ohm value again and it did not register. I temp grounded the rca shield to the HU housing and then plugged it into the amps via a split cable. The wire grounding made no difference, you could still hear the slight buzzing/whine through the mids, tweets, and barely through the subs, with the volume all the way down. Maybe its just my vehicle?

ppia600 · 29th November 2007, 05:09 AM

Oh My Gosh... I thought you tested the head unit's rca grounds a long time ago

Ding, ding, ding. I sure hope they are actually fried, that will probably take care of everything. We've been all running a wild goose chase

Perry Babin · 29th November 2007, 10:53 AM

Unplug the RCAs from all components on both ends. Make sure none of the ends are in contact with the vehicle or anything that is conductive. Measure the resistance from each of the shields of the RCA cables to chassis ground (black lead on a known good ground). You should read infinite resistance. If you read something near 0 ohms, the RCA cable is pinched/shorted to ground.

On the head unit end, ground both/all RCA shields to the head unit (I'm not sure if you have more than one RCA cable going to the rear of the vehicle). They have to be grounded. You can't do any troubleshooting with ungrounded shields.

After you have the shields grounded, plug the RCA cables into the highs amp ONLY. Does it have noise?

Unplug it from the highs amp and plug the RCAs into the sub amp. Does it have noise?

28th November 2007, 05:35 PM	#91
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	http://bcot1.com/images/rca/temporar...eldrepair.html __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th November 2007, 05:54 PM	#93
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	You should have approximately 0 ohms when you touch one lead to the RCA shield and the other lead to the case of the head unit. You need to do this with all RCA cables disconnected from the head unit. Set the meter to the lowest ohm range. Touch the leads together to make sure the meter is working properly. You should read 0 ohms when you touch the leads together. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th November 2007, 06:43 PM	#95
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Was the EQ still in the circuit when you grounded the RCAs? Without fusible shield grounds, if the RCA cables contact the main power wire, the RCA cable will burn from one end of the vehicle to the other. It's a fire hazard. This used to be relatively common before the shields were fused. I see a lot of people who pull their amp but don't pull the main power fuse and don't tape up the power wire. While driving, the wires (RCA cables and power wire) slide around in the trunk. Eventually they make contact. Don't cut the insulation. The connection is between the RCA patch cable connector and the case of the head unit. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

28th November 2007, 07:03 PM	#97
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If the EQ was in the circuit and was defective, repairing/restoring the shield ground of the head unit could not stop the noise because a second defective component was in the audio chain. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

29th November 2007, 05:09 AM	#99
ppia600 diyAudio Member Join Date: Jun 2007 Location: Louis y ana	Oh My Gosh... I thought you tested the head unit's rca grounds a long time ago Ding, ding, ding. I sure hope they are actually fried, that will probably take care of everything. We've been all running a wild goose chase __________________ Don't worry... you can always turn the gain down!


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th November 2007, 05:43 PM	#92
pityocamptes diyAudio Member Join Date: Sep 2007	So your saying that the no ohm value means I have an open ground? I checked the HU while in the dash. Should I have pulled it out? Thanks again.

28th November 2007, 06:16 PM	#94
pityocamptes diyAudio Member Join Date: Sep 2007	OK. I will double check again later. I do remember connecting the rca shield to ground and the noise got even worse, but I only did it with one of the rca outputs. Thanks. **Oh, is this a common occurance? Why would HU manufacturers fuse the ground, and not just run a solid trace? Also, my preamp outputs on the Jensen HU are about 6" wires straight out the back that end with an RCA plug. I noticed the pictures you had were a little different. Should I break the insulation and solder to the shield, or should I solder a line off the rca shield as you depict?

29th November 2007, 02:13 AM	#98
pityocamptes diyAudio Member Join Date: Sep 2007	Hi. I checked the ohm value again and it did not register. I temp grounded the rca shield to the HU housing and then plugged it into the amps via a split cable. The wire grounding made no difference, you could still hear the slight buzzing/whine through the mids, tweets, and barely through the subs, with the volume all the way down. Maybe its just my vehicle?

29th November 2007, 10:53 AM	#100
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Unplug the RCAs from all components on both ends. Make sure none of the ends are in contact with the vehicle or anything that is conductive. Measure the resistance from each of the shields of the RCA cables to chassis ground (black lead on a known good ground). You should read infinite resistance. If you read something near 0 ohms, the RCA cable is pinched/shorted to ground. On the head unit end, ground both/all RCA shields to the head unit (I'm not sure if you have more than one RCA cable going to the rear of the vehicle). They have to be grounded. You can't do any troubleshooting with ungrounded shields. After you have the shields grounded, plug the RCA cables into the highs amp ONLY. Does it have noise? Unplug it from the highs amp and plug the RCAs into the sub amp. Does it have noise? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Need help troubleshooting whine in speakers	roger2	Car Audio	5	19th May 2009 05:22 PM
Help! t-amp in car, alternator whine	ractis	Car Audio	4	25th February 2006 05:51 PM
'03 Accord - Alternator Whine	Pete H	Car Audio	5	30th June 2005 04:02 AM
Engine whine	feelinhipp	Car Audio	3	13th March 2004 05:53 AM
Can someone help me with alternator whine?	Timbers	Car Audio	14	23rd February 2004 05:14 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read