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Old 2nd June 2010, 03:10 PM   #1
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Angry noise issue on rockford rfx 8140

hello all , newbie here

ive just fitted a rockford rfx 8140 , its all good except one thing

each time i change tracks i hear the motor/laser noise from the unit through the left speaker

ive tried swapping around the phono leads , and the whole system was fine with my other headunit

can anyone make any suggestions towards a fix ? id dearly love it to be silent ...the molex plug for the phonos isnt the greatest , could that be the problem?
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Old 2nd June 2010, 04:23 PM   #2
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Is the noise always on the left speaker, no matter which RCA plug (L/R) is connected to the left channel of the amp?
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Old 2nd June 2010, 04:27 PM   #3
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no , if i switch them around it travels , so its looking like the headunit or the fly lead for the rca 's

someone has suggested that i ground the external tube part of that left rca , and see of that helps...anyone agree?

thanks

Last edited by steveo3002; 2nd June 2010 at 04:31 PM.
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Old 2nd June 2010, 05:41 PM   #4
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Try swapping the RCAs at the head unit. If it change sides, it's likely a head unit problem. You can measure the resistance from the RCA shield on the head unit to the case of the head unit. Both channels should read the same (generally 0 ohms).

Grounding the shield won't do any damage. Ground it before turning the system on. If the shield is open and you ground it while it's on, it could cause a significant transient (pop).
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Old 2nd June 2010, 05:52 PM   #5
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thanks for that , will check it out

if it points towards a head unit fault is it likely to be something fixable for reasonble $$ considering its age
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Old 2nd June 2010, 06:15 PM   #6
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An open shield would be a simple repair in most cases.
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Old 3rd June 2010, 05:50 PM   #7
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okay ive checked it out as you instucted me to

ground the headunit chassis ...maybe a small improvement (not sure)

extra ground on main harness..no change

ohm meter on rca outer shield to headunit chassis , 0.2 ohm (cheap meter ) same on all rca leads

ground rca outer sleeve...much worse noise , effects both if grounded
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Old 3rd June 2010, 08:33 PM   #8
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Check with Rockford to see if they have a schematic diagram.
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Old 3rd June 2010, 08:57 PM   #9
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ok i have submited the question to rockford

are you suprised the noise gets worse when i ground the outer part of the rca?
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Old 3rd June 2010, 09:52 PM   #10
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The manual mentions balanced operation for the RCA signal but doesn't give much detail. I would like to see the circuit so I can understand it better. If it was set up for balanced operation and you grounded the shield, it could cause the noise to get worse. Since you read ~0 ohms to ground, it's not likely set up for balanced operation. I don't know if the schematic diagram will help but it should eliminate some of the guesswork.

Does the left front AND the left rear have the noise?
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