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Topic: 60Cycle Hum With Inverter On (Read 1654 times) previous topic - next topic
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60Cycle Hum With Inverter On

Yahoo Message Number: 548
When we are on the road and have the inverter turned on, TV on and Sat receiver on we get a loud "60cycle hum" through our (standard-not a Bose system) DHS MOBILE THEATER SYSTEM. When we stop at a campground and plug into a 50amp outlet and turn the system on we hear "no hum".

It could be a grounding problem with the Inverter System, but I have no idea as to where to check, etc.

Any advice would be appreciated.
Thanks Den

Re: 60Cycle Hum With Inverter On

Reply #1 –
Yahoo Message Number: 549
Quote from: @y\.\.\.
When we are on the road and have the inverter turned on, TV on and > Sat receiver on we get a loud "60cycle hum" through our (standard-

not

Quote
a Bose system) DHS MOBILE THEATER SYSTEM. When we stop at a > campground and plug into a 50amp outlet and turn the system on we > hear "no hum".

It could be a grounding problem with the Inverter System, but I

have

Quote
no idea as to where to check, etc.

Any advice would be appreciated.
Thanks Den

Den

One thing i have found on ground and power line/cables is the star washers that are used. They tend to corrude and create hard to fine problems. I remove these washers and either use a flat washer or a lockwasher.not sure if this is your prob. but its worth a try Ed.

Re: 60Cycle Hum With Inverter On

Reply #2 –
Yahoo Message Number: 550
Thanks, I'll give it a good look and replace those washers.............I'll try ANYTHING...
Den

Re: 60Cycle Hum With Inverter On

Reply #3 –
Yahoo Message Number: 555
Quote from: @a\.\.\.
Thanks, I'll give it a good look and replace those
washers.............I'll

Quote
try ANYTHING...
Den
If I were you, I would NOT replace the star washers with flat or lock washers. That's a VERY bad idea. The purpose of the star washer is to 'bite' into the metal and make a solid connection through the surface corrosion and/or paint on the metal. Flat washers do not cut through the paint and/or corrosion and therefore do not make a good connection. If rust builds up on a star washer, it can be replaced.
However, the rust is an indication you need to weatherize this connection. The connection can be painted or better would be to use the same 'goo' that is used on battery terminals to stop them from corroding.
 

Re: 60Cycle Hum With Inverter On

Reply #4 –
Yahoo Message Number: 559
I wouldn't think the problem is a GNDing problem with the inverter. If that were the case you would surely notice more problems than just a 60HZ audible hum.
The problem is more likely a GNDing issue with one or more of the components you are using to watch TV. Since you have a Sat dish, there is probably an A/V switcher installed to switch between the VCR, SAT, etc. One-by-one remove each component connection on the back of the switcher. Listen for the 'noise' to go away or be significantly reduced. If the 'noise' goes away, the connection you just removed is causing at least some of the noise problem. At this point reconnect and run a temporary GND from that connection to a known good GND. A GND bar is probably not a good enough GND. Using a star washer run a self tapping screw into the chassis or run the jumper wire back to the battery or transfer box. This should make a common GND between all the devices that are connected to the switcher. That's assuming the coax and/or RCA plugs connected to the switcher are in good condition and have good sheilds.
If the common GND doesn't work or only reduces the noise, try a ground-loop isolator on the audio between the TV and the amplifier.
The isolator should be installed on the TV side. I've heard of an instance where the TV was removed for some reason and when it was reinstalled the TV was set on top of the isolator wires. Over time the wire insulation was cut and the coach audio system got a horrible background hum. Replaced the ground-loop isolator and no more noise. I wouldn't recommend a ground-loop isolator with the Radio Shack brand name.
Hope this helps.