TrailManor Owner's Forum - View Single Post

07-06-2003, 02:26 AM

Interesting...

Putting on the EE cap, three things I would check next:

1) Is the converter OK?  Since I'm certain you can't put a scope on it, at least check it for DC voltage.  You should find about 13.5v [the battery charge voltage when plugged in] on the accessory circuits and about 12.6 volts on the other 12v circuits.  You might see two big button diodes on an aluminum plate inside the converter.  It could be that one of these fails but checking this requires some expertise.  If all your appliances work well and the battery charges up fine then I would tend to discount this.

2) Ground loop carrying current or an appliance causing interference?
I think you've checked this already.  Shut off the AC breakers one by one, even the main one, and see what happens.  Also, pull each DC fuse one by one.  

2) Is the RFI emitted or conducted?  If the hum persists using a separated power supply to the radio, the interference mightbe through the antenna.  Usually though a 60Hz hum is a [conducted] power supply issue.

3) Check the routing of the speaker wires.  Although unlikely although it is possible that the speaker wires could be closely coupled enough to pick up.  Such a hum source would be also present with the stereo off.

07-06-2003, 02:26 AM	#10
tipper Guest Posts: n/a	Re: Hum in the Cassette/Radio Interesting... Putting on the EE cap, three things I would check next: 1) Is the converter OK?  Since I'm certain you can't put a scope on it, at least check it for DC voltage.  You should find about 13.5v [the battery charge voltage when plugged in] on the accessory circuits and about 12.6 volts on the other 12v circuits.  You might see two big button diodes on an aluminum plate inside the converter.  It could be that one of these fails but checking this requires some expertise.  If all your appliances work well and the battery charges up fine then I would tend to discount this. 2) Ground loop carrying current or an appliance causing interference? I think you've checked this already.  Shut off the AC breakers one by one, even the main one, and see what happens.  Also, pull each DC fuse one by one.   2) Is the RFI emitted or conducted?  If the hum persists using a separated power supply to the radio, the interference mightbe through the antenna.  Usually though a 60Hz hum is a [conducted] power supply issue. 3) Check the routing of the speaker wires.  Although unlikely although it is possible that the speaker wires could be closely coupled enough to pick up.  Such a hum source would be also present with the stereo off.