The Steel Guitar Forum

I've got one of the last Nashville 400's made, And it's a workhorse of an amp but It has developed a little problem. After I've been playing it a while it will develope a loud humming or buzzing sound and the compressor light will stay on. If I turn off the reverb it goes away. Well, I experimented today when it started and I pulled up on the reverb wires and it quit. Now I've already cleaned the molex connector and the rca connections at the pan. My question is, Could the cord be bad? And if so, Where is a good scource to get this. I'd buy a used one from somebody if I thought it would cure the problem.
Thanks and Merry Christmas!!

Mike, the shielded part of the cable goes bad and causes the hum you heard. Replace the cable with a decent grade of shielded cable and you'll be good to go.

The female Molex connector pins can "spread" and not make good contact with the pins on the circuit board. This is especially true if it happens after it's "warmed up". Reforming the pins so they make tighter contact can also help.

Already done that Jack. Did that when we cleaned the connections. I'm gonna find me a new cord with the rca's on one end and the plastic molex connector on the other and try that now. I hope I can find one somewhere.

Another fairly common problem is the solder joint on the circuit board where the reverb connectors attach. It frequently gets loose and requires just a re-solder to repair it.

Good point, Jim. If there is a "hairline" crack it may not show up until the unit is heated up and the metal tends to expand.

Also, when it happens wiggle the Molex connector to see if that makes a change. If it does, the problem is either still in the plug or as Jim mentioned a bad solder joint on one of the pins (probably a ground pin).

I "permanently" fixed the Molex connector problems on my NV400 by wiring RCA Jacks on to the circuitboard Molex Pins (with short shielded wires) and then used different shieled cables with RCA plugs on both ends between the Reverb Pan and the RCA Jacks for the Reverb I/O.

I soldered the wires to the pins and got rid of that troublesome Molex connector.

the subject of a cold solder joint came up before with someone here in town but, what makes me think it's the cord is i can just touch the cord about mid way or toward the pan end of it and it straightens right up. usually it happens after i play a bunch of heavy low ended chords. i guess it shakes the cord. if this doesn't cure it i'll get those molex connectors re soldered.

don't play those chords

i can't help it .

I'll be home late tomoro nite Mike !! I can fix it or either replace it !!

Thanks Tommy. I'll see you when you get back. I'm working a triple tomorrow and a 2-6 Sunday so just try my cell.

Ernie Fair needs steel @ Legends tonite 10-2pm

Wish I could do it Tommy but Teresa is very sick. I'm trying to nurse her back to health. We didn't even go to her folks today. She's been in bed most of the day.

Well, Tommy's got two of my amps now doing surgey. One is the amp in question here and the other is my very dear '76 session 400. It has at least 1 cold solder joint but he's gonna fix it too. One thing he's gonna do to the nashville is going to be interesting and after I've had a chance to test drive it a day or two I'll tell you what it is. It's a very simple thing. But I'm looking forward to seeing how it works.

Mike, Really enjoyed u hanging out with us at Layla's and enjoyed listening to you play with Monte and his great band last nite !! You guys were awesome. Just dont get any better. Monte should be proud !!! Best D@mn band on Broadway byyyyy far !!!

Mike, thought I'd jump into this thread and say that I really enjoyed listening to you play with Monte at the Wheel when I was in town on the 19th. Great playing. You and the guitarist (what's his name again) made the night for me. Many tasteful and tasty licks coming from you guys.

Alan,

It was great meeting you too. That guitar player is James Mitchell. He's one of the up and coming session players here in town. I don't know why he would want to play with a hack like me but we do have fun.

Tommy,

Thanks for hanging out and for the fabulous job you did on my nashville 400. It has never done better. Now I can keep up with those guitar players and drummers. LOL!!!!!
And thanks for taking the govenor off like I asked you to. Now it don't squash down when I hit a #9 chord. Bless you!!!!
Guys I don't remember what all Tommy said he did to the amp but maybe he'll see this and chime in.
Thanks again Tommy.

Nothing more than what the great Ken Fox taught me!! The Nashville 400 is one tough amp!!! and I'll have to say Mike yours is one of the better sounding ones I've heard!!

The Peavey reverb tanks have what is known as an isolated input. The input coil is isolated from the tank's metal container to avoid a ground loop hum. As John Lemay stated that needs to be a good quality cable! The tank's output connector is grounded to the tank's metal case to provide shielding of the signal as it passes through the tank. If the input looses it shield connection or is weak in its connection to the tank's RCA input connector a lot of hum is produced.

I also recently bought a brand new Accutronics tank that was in fact built wrong! They forgot to put the insulating wafer behind the input RCA connector and it was grounded to the tank! This tank squealed like pig when connected. Fortunately I had an old tank and used the insulating wafer out of it to correct the tank. It was real happy once that ground loop was broken.

The fist thing I do when I have reverb troubles with a Peavey amp (and it happens more times than not!!) is to pull the cable at the amp end and verify continuity to the tank's input and output coils with an ohm meter. If I see an open on either one I verify the cable from the Molex connector do to the inside of the tank at the back of the RCA connectors. If that is good I check for an open coil or a dirty connection to the RCA jack.

After that I re-tension the Molex female pins on the reverb cable harness. I have repaired many a Molex connetor (I keep new pins and Molex parts in stock). I have yet to have a bad cable, but it is not out the question to happen. I agree with John, the quality of the cable used is marginal.

A small dab of bulb grease from the local auto parts store on the connections can prevent future oxidation of the contacts, insuring a longer period of trouble free reverb operation.

Bottom line, I have learned to hate spring reverbs! I turn them off in any amp I use, including vintage amps and use my RV-5 or my new Digitech RV-7.

Even after serving the reverbs on N-400 amps I have modded there have been issues when they get back to the customer. Typically they just unplug and replug the tank and all is OK.

There just has to be a better way short of soldering the leads to the pins on the bottom of the amp, I just have not found it yet!!

The funny thing is, Tommy said the reverb was fine it was other things causing the reverb to do what it was doing. It's fine now and has never sounded better.

Mike tell me buddy, do u think the right Nashville 400 is capable of producing tube like harmonic frequencies ?? Or at least tricking your ears into thinking u are hearing tube like qualities??? LoL

Can you tell me how to turn off the so called 'governor'? I'm not fond of the "squash" either.
Thanks.

Me either Joe ??? Hmmmm m I gettn blamed for that IDK ??

Tommy R. Butler wrote:Mike tell me buddy, do u think the right Nashville 400 is capable of producing tube like harmonic frequencies ?? Or at least tricking your ears into thinking u are hearing tube like qualities??? LoL

Tommy, the new mod that Ken Fox is doing to these amps comes very close to that! The difference is night and day, including the reverb.

The mod that Ken does is way different than the Peavey or Lemay mods, and involves quite a few component changes. I believe there's about 38 parts in total on this upgrade. Look here: http://foxvintageamps.com/classic_green_004.htm