location for mx-7777

[alphaseventwo]

I have finally collected the cables/components for installing a mx-7777 into the mix for use with a vic-1, and some auxiliary power needs in the old m998. Anyone have suggestions as to a good location for this monster? The power to battery cable is 10', and the power to radio cable is 5' -so I'm thinking I'll have to keep it close. Perhaps behind/under the radio tray? I'd prefer to not just put it on top of the tray. I'll admit I havent spent any time searching TM's for this, but off hand could not remember seeing it in the -10.
Thanks All.

This is what I'm working with.

 

[cruzinz28]

I have mine mounted under the radio tray with the on/off switch facing the driver. I will see if I can get a picture of it tonight when I get home and post a better picture tomorrow.

If you save the picture you can zoom in and just barely see the on/off switch. It is mounted horizontally using the same bolts that mount the amplifier and/or the intercom box on the vertical plate.

 

[Augi]

Those are for tracked vehicles that have heavy loads switching on and off that inject noise into the system. They never put them in HMMWV's because you don't need them.

Augi

 

[papakb]

Augi's correct here. The MX7777 and it's little cousin the MX7778 were designed primarily for use in tracked vehicles where you have large solenoids kicking on and off that produce lots of electrical transients that can damage radios. This would also hold true for trucks like wreckers. In practical use the useful thing about the 7777 is the on off battle override switch that the 7778 doesn't have. As for an on off switch, just use the one on the front of the 1780.

I guess if you have to have it the best mounting location would be on the auxilliary tray behind the panel the 2298 and 1780 mount onto.

 

[alphaseventwo]

Hmmm. Good thing I "collected" all the parts- lol. I am still thinking of using it- for 1, I have a fair amount of alternator 'whine" coming through the headsets that I believe will be remedied by the 7777. And secondly, I've seen them used with a step-down unit (24v to 12v) for running accessories. It has two outputs- I figure one for vic-1, the other for 12v stuff. If it dosen't work out, there'll be a seriously discounted complete unit (or 2) available. If the alternator whirring does not resolve, I guess it will be time to upgrade that...

 

[Augi]

I had a lot of bad alternator whine in my VIC-1 also. However I didn't have a radio in the system when I was using it.

I still get noticeable whine in my VIC-3 but it's less severe. It whined when I had the 60a alternator installed and still now with the 200a. There must be some good filtering in the VRC-12 radios because when I have the radio in the mount it significantly reduces it to the point that I only hear it during low RPM acceleration and even then it's not too noticeable unless you are listening for it. Once I'm above 1500 or 1800rpm the pitch is high enough that you can't hear it anymore. When I pull the radio out, it gets very noticeable again.

Before I had radios I tried some power line filtering with no luck. Once I got the radios they cleaned it up to the point where I never notice it anyway and since they are more or less permanently in the system my problem is solved.

The whine does get transmitted over the radio because guys on the other end can tell when I'm accelerating in street traffic.

Augi

 

[papakb]

There's no noise filtering or voltage regulation going on in stock 7777 & 7778 transient suppression units. They're only there to keep any transients in the electrical system below a certain voltage to prevent damage to sensitive electrical equipment like radios. If you saw one that does voltage regulation then the owner installed a regulator internally to do that function. It's a simple matter to do that but because of space limitations you'd have to remove the transient suppression diode to make room for it.

Is there a market for something like this that does voltage regulation? Maybe it's a project worth taking on. How about some feedback here?

 

[jeffhuey1n]

Interesting information. Wish I’d seen this before my experiment with my 7778. Oh well, live and learn. The question I have is what can I use inline to provide circuit breaker protection for my radio and Vic-1? I have these circuit breakers. There’s a 30 amp, 25 amp and 3 15 amp circuit breakers. Would one of these spliced into the 1780 power cord provide that protection? I’ve been looking at books till my eyes are bleeding but can’t make heads or tails of the issue. Pics of the C/B’s below: