Velodyne Ct100 Loud Hum -Help needed

[joemana]

I'm working on Velodyne Ct100 with very loud hum.
Here is what I've done so far.
1. I disconnected the sub with nothing attach on it and turn the control volume to max =NO Hum.
2. I reconnected the sub cable only =Hum.
3. I connected two known (tested on the other sub with no problem) good cable = Hum.
4. I connected the original Velodyne cable that failed on system to other Sub = NO Hum.
4. I removed the amp plate and visually checked for obvious sign problem such as cold solder, burnt cap or other components didn't notice any.
Is there anyone who have experience this problem before and what fix did you do?

Thanks,

Joe

[subynube]

The original cable that came with the Velodyne sub (the one that didnt hum) sounds like it had a 3rd prong (ground prong) and the others did not. Is this the case? Sounds like a grounding problem to me.

[ahaik]

I'm working on Velodyne Ct100 with very loud hum.
Here is what I've done so far.
1. I disconnected the sub with nothing attach on it and turn the control volume to max =NO Hum.
2. I reconnected the sub cable only =Hum.
3. I connected two known (tested on the other sub with no problem) good cable = Hum.
4. I connected the original Velodyne cable that failed on system to other Sub = NO Hum.
4. I removed the amp plate and visually checked for obvious sign problem such as cold solder, burnt cap or other components didn't notice any.
Is there anyone who have experience this problem before and what fix did you do?

Thanks,

Joe

Check the RCA connectors ground (on the plate amp or preamp), it may have a cold solder joint.
To check the Preamp (or reciever) Check connectivity with the sub output RCA (on the Preamp) to other RCA connectors (on the Preamp), the grounds should be common. If not, you probably have a cold jonit.
For the amp I'm not sure
I had a similar problem (very very loaud hum) and it turned out that the ground solder joint was broken at the RCA connector.
This usually happens when using tight RCA connectors.

[joemana]

All three (original cables included) cables makes hum when I plug it in to Velodyne sub but not on the other sub.

I've inspected the RCA solder joints under the microscope, it has very good wetting in it, then I ohm it and every pins have good contact.

I will re-solder the solder joints, maybe the poor contact is not just visible and hope this will fix it. Thanks guys.

Joe

[Biff]

What happened prior to getting the hum - new location, system arrangement? You said you hooked it up with sub cable only and got hum - what was that cable coming from? When I have experienced this in the past most times it was coming in from the cable connection into the receiver and disconnecting cable from the HT stopped it, and an isolation transformer (about 10 bucks at PE) fixed it. GL

[joemana]

My cousin disconnected most of the cable on the system including sub cable and accidentally hooked it to center channel (no system relocation) and later found out a loud humming sound when he turned ON the unit. The system was working fine before he disconnected the cable.

I connected one end of the cable to the sub and the other was not connected anywhere . I also tried to connect it to my receiver and got the same results=Hum.
The humming sound get loud as I cranked up the volume control of the sub, if you set it to minimum there is no hum.

[ahaik]

Is there music too or only a hum ?

[joemana]

THANK YOU ALL...

Finally found the problem after I de-solder the RCA connector. The ground pin is broken in between amp pcb and RCA housing. It's not visible outside and when I Ohmed it, maybe, I pressed hard and made a contact that's why I thought there is no problem with that initially.

Joe