You can check the rca grounds, Those amps are popular for the ground pins on the actual RCA connector breaking off. there is also the topaz circuit which connects the power ground and signal ground together using a general purpose diode and 1K ohm resistor in parallel. You can check this ground with a multimeter without opening the amplifier. If you put the meter on the diode check setting unplug your RCA's and put one lead on the power ground on the amp and the other on the outter shield of the RCA connector(of the amp) you should be able to read that the diode is in place. It will read about about half volt in one direction and close to one volt if the leades are reversed. If you read open then the ground pin on the RCA connector broke off or the ground trace has burned, very common problem when there is not a solid ground.
You may have an open shield on the head unit.
http://bcae1.com/images/rca/temporaryrcashieldrepair.html
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
Also confirm that you have 0 ohms continuity between all of the RCA jacks on the amp (no RCAs plugged in).
http://bcae1.com/images/rca/temporaryrcashieldrepair.html
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
Also confirm that you have 0 ohms continuity between all of the RCA jacks on the amp (no RCAs plugged in).
it's in the amp not the rca's. The first thing i checked was the rca's and my ground's and the resistance between battery ground and where i grounded the amp and it was 0.02resistance so i pulled the 600a4 out and put my 800a2 in and there was no engine noise with the 800a2 when the car is running so i know the problem in the 600a4.
The following still need to be checked (from the previous post):
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
Also confirm that you have 0 ohms continuity between all of the RCA jacks on the amp (no RCAs plugged in).
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
Also confirm that you have 0 ohms continuity between all of the RCA jacks on the amp (no RCAs plugged in).
that was the first thing i checked was the rca ground on the radio when the engine noise started and it 0 ohms and i checked the amp ground to the rca ground on the amp to see if the ground lead broke off the board in the amp and it good to it's at 0 ohms and i checked the rca's to 0.01 ohms so everything from the radio to the amp that why i pulled the 600a4 and put my 800a2 in and there no engine noise with it so i put the 600a4 back in and the engine noise is still there so something wrong internal with the 600a4.
i will just send it out and get it fixed.
From a previous post:
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
You should also confirm that there is no direct connection between the RCA shield of the amp and the chassis ground terminal of the amp. Unplug the RCAs from the amp and measure the resistance from the shield of the RCA jacks to the chassis ground terminal. You should not read anything near 0 ohms.
If you read ~0 ohms from the amp's input RCA shield to the amp's chassis ground with no RCAs plugged in, you have a shorted diode in the amp. It needs to be replaced. I don't have any information on the 600a4 but it's likely D3. It would probably look similar to the diode in the attached photo.
Attachments
Ok i found the bad diode and replaced it now it reads 952ohms from the amp ground to the rca ground shield it's to late to night to put it back in and test it so i will hook it back in the morning and i let you know if that fixed the engine noise.
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