VIC-3 whistling noise with Engine rpm

[engele]

Hi,
i have a VIC-3 full station in my Humvee.
i have a whistling Noise in my headset depending the rpm of the Engine.
only in Live, VOX or PTT if the PTT is on.

anyone have the Same issue? I think its Not normal.
greetings

 

[milradioman]

Sounds like alternator whine, which may be a defective alternator, (bad diode?) it may charge ok, but still cause the whine.
Where is the power connected?
Check grounding location(s)
You could install a filter, but better to eliminate the source of the interference.

 

[US6x4]

I have that same sound in my M813's VIC-1; kinda sounds like the truck has a turbo. Would a filter simply wire inline with the positive cable for the 1780 amplifier?

 

[US6x4]

Does anyone know of a good heavy duty filter that would eliminate that noise?

 

[Augi]

Try improving the grounding. I ran a big flat ground braid from one of the feet of the main control box back to the battery and it reduced the whine significantly.

Augi

 

[US6x4]

When you say "main control box" are you talking about the truck's PCB or the AM-1780?

 

[Augi]

I'm talking about the CD-82 for the VIC-3. You can try the same with the AM-1780. Remove the paint where you attach the ground strap.

Augi

 

[US6x4]

That would help a lot since, after looking back, my 1780 has rubber spacers between it and its panel...

 

[86humv]

I've tested the vic-3 on a bench power supply...and had a whine when only positive and negative were hooked up...then I grounded the main control box to the chassis ground wing nut on bench supply....no more whine.

 

[US6x4]

Side note: I added a 6 gauge ground cable back to the battery and that cured the whine in my VIC-1.

 

[The King Machine]

Ok,

Thats a sweet Comms set up

 

[US6x4]

Ok,

Thats a sweet Comms set up

Thanks! - I like it. Here is the write-up I did on it a while back.

 

[RJTM998]

Side note: I added a 6 gauge ground cable back to the battery and that cured the whine in my VIC-1.

View attachment 848451

I tried this and it didnt work. I have been chasing this whine thing for almost a year. I was hopeful this would fix it. I have installed a filter that helped a little, I have grounded to different positions from the battery, the shunt, the engine block, and still no luck. At this point I am guessing a bad diode in the altenator.

 

[US6x4]

FWIW...I ran my ground cable from the AM-1870 attaching bolt (1 of the 4) to the same battery ground terminal that the AM-1870 power cable was wired to.

 

[RJTM998]

FWIW...I ran my ground cable from the AM-1870 attaching bolt (1 of the 4) to the same battery ground terminal that the AM-1870 power cable was wired to.

I put both grounds to the shunt. Not sure if moving both to the battery will help but may try that. What's weird about mine is it is worse sometimes than other times.

 

[RJTM998]

FWIW...I ran my ground cable from the AM-1870 attaching bolt (1 of the 4) to the same battery ground terminal that the AM-1870 power cable was wired to.

I am wondering if I could have a faulty CX-4720 power cable?

 

[Mogman]

That would help a lot since, after looking back, my 1780 has rubber spacers between it and its panel...
View attachment 826439

Man that is some awesome work on that VIC-1 system, VERY-VERY nice!!
I don't have the patience or skill to do that level of work.

 

[US6x4]

Man that is some awesome work on that VIC-1 system, VERY-VERY nice!!
I don't have the patience or skill to do that level of work.

Well, thank you! I took my time on it and it turned out nicer than I had hoped. Here is the writeup I did on it awhile back:

https://www.steelsoldiers.com/threads/vic-1-intercom-panel-for-soft-tops.188122/

 

[RJTM998]

RJTM998
Well-known member
I figured out the alternator whine. When I mounted the crew boxes I screwed them into the wood on the tunnel but got into the actual metal floor and caused a ground loop. For those with this problem check your mounting points. Once I removed the screw that was touching the tunnel through the wood it went away. You might need to insulate your mounting points so no metal to metal contact.