Reverb humming

Ricky Hagan · Post by **Ricky Hagan** » 28 Aug 2005 3:06 pm

Does anyone know what i can do to fix this problem.I have a Nashville 400 amp(mid 80's)The amp works and sounds great.The problem is the reverb unit hums so bad.I take the reverb out of the back of the amp and let it set on the floor or a chair and it works great (no hum) I know this sounds crazy but I have tried everything with no success.I had a Friend to recover the amp but that should'nt cause this problem I would'nt think. Any help will be gladly Appreciateed

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Jerry Overstreet · Post by **Jerry Overstreet** » 28 Aug 2005 6:14 pm

Was the tank removed when your friend recovered your amp? You might try rotating the unit end for end [180°] if you haven't already. One direction will be noiser. Else check for bad shielding of the cables or plugs.

You've probably already done this, but it might be a good idea to check the connection at the amp's white molex plug too.

Sounds like it's picking up noise from the transformer if it goes away when you take it out of the amp.

Mike Brown is the resident Peavey expert here so he may have some other/better suggestions for you. [This message was edited by Jerry Overstreet on 28 August 2005 at 07:25 PM.]

Ricky Hagan · Post by **Ricky Hagan** » 29 Aug 2005 2:11 pm

Thanks Jerry

Gary Preston · Post by **Gary Preston** » 5 Sep 2005 9:31 am

Hi Rick . I have two of the Nashville 400 amps ,one i bought new and the other one is used and they both have a bad hum in the reverb . It seems to me that they all have a bad hum . I can turn the reverb off and the amp is quiet as a mouse . It's a crazy thing to me but it is also a bad thing to put up with . I hope that Mike Brown has a way to fix this problem . Other than that it's ok . Best regards , Gary .
P.S. two of my friends also have the same problem with thier amp . [This message was edited by Gary Preston on 05 September 2005 at 10:35 AM.]

Blake Hawkins · Post by **Blake Hawkins** » 5 Sep 2005 11:36 am

Ricky,
Hum is not normal for the NV400 reverb.
Mine does not have it. Several I've worked on didn't have it. On one that did, it was the molex connector. Cleaning and adjusting it was the fix.
Jerry has given some good advice which should help you find the problem.
Recently I installed a friend's NV400 chassis in one of Jerry's cabinets which allows the head to be separate from the speaker.
Even though the reverb tank was closer to the chassis than in the stock cabinet, we did
not have a hum problem.
Blake

Lanny Carnley · Post by **Lanny Carnley** » 6 Sep 2005 8:14 pm

Yeah, I've got a Nashville 400 I bought new in 95. It's had a hum like that since day one. It's been back to the factory 3 times. It doesn't seem to hum when they check it at the factory. Guess some 400's have it and some don't.

Jack Stoner · Post by **Jack Stoner** » 7 Sep 2005 2:31 am

I had a hum in my NV400 reverb circuit from the time it was new and Peavey worked on it, in warranty, and couldn't "hear" it.

I did a lot of work on it and finally found a hairline crack in the Printed circuit for one of the ground molex connector pins on the circuit board. After repairing that, no more hum.

It should not take a (qualified) tech long to find it, if that is the problem. An ohmmeter or continuity tester is all that's needed.

It may be something else, such as a bad ground connection in the actual molex connector, too. But, it's going to take some troubleshooting with at least an ohmmeter to determine where the problem is, if it is a ground/wiring problem.

David Doggett · Post by **David Doggett** » 7 Sep 2005 12:45 pm

There have been several posts in the past on this problem in these amps. They all say that the first thing to do is clean off the molex connectors. Sometimes just unplugging them and replugging them a few times does the trick. It did for mine.[This message was edited by David Doggett on 07 September 2005 at 01:46 PM.]

Chris LeDrew · Post by **Chris LeDrew** » 7 Sep 2005 5:07 pm

I had a similar problem as well with my Session 400, and Mike Brown told me (over the phone) to reach behind the amp and switch around the cables that connect the reverb to the amp. Presto - quiet as a mouse.

So they're called "molex connectors"...you learn something new every day on the forum.

[This message was edited by Chris LeDrew on 07 September 2005 at 06:10 PM.]