Session 400 Problem

Rob Segal · Post by **Rob Segal** » 2 May 2001 4:47 am

I have a '65 Session 400, pre-paramtric, which I dearly love. Problem is, it has developed an intermittent hum. If you smack the amp good in the right place, it will become absolutely quiet. The right place varies, unfortunately--takes a good few knocks to get it to quiet down. But then, when you move it or jar it, it comes back.

I'm guessing there is a bad connection somewhere, but I am wondering if anyone has some experience with this on the Session 400, and where the typical problem connections are, or how to go about finding the problem.

Thanks,

Rob Segal
Zum D-10
NYC

Larry Bell · Post by **Larry Bell** » 2 May 2001 6:13 am

First thing I'd do is check all the molex connectors between the amp and the reverb tank. Common place to find gremlins.

Remove each connector and spray some De-Ox-It or contact cleaner on the plug, replace, and twist to clean off the contact points.

May not solve your problem, but can't hurt.

LTB

Jack Stoner · Post by **Jack Stoner** » 2 May 2001 6:54 am

Some of the older Session 400's had RCA phono connectors for the reverb (they were made before Peavey discovered Molex connectors). There are some internal connectors that could be checked, but I'd suspect it is more than a connector problem.

Jim Eaton · Post by **Jim Eaton** » 2 May 2001 8:53 am

Is that a 75' Session 400? I don't think they made them in 65'.
I have an early 70's Session 400 and the reverb connections are RCA's on it.
I had a similar problem with mine, but only after it got dropped off a loading dock in Lake Tahoe! The "spot" to wack it would not be the same from night to night, weird.
My amp is on its way to John LeMay for a rebuild as I write this. My hands can't take it anymore!
JE:-)> <FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Jim Eaton on 02 May 2001 at 09:55 AM.]</p></FONT>

Rob Segal · Post by **Rob Segal** » 2 May 2001 9:27 am

Jim, you're right, it's from '75 or so, my mistake. The reverb connectors are phono type. I've disconnected the reverb, it sounds kind of crappy, I use an SE-70 or VF-1. Peavey told me the amp can be run without the reverb in line with no problem.

The "whacking" hand gave out a while ago, I use a screwdriver handle now. I'm going to take it out of the cabinet, hook it up to the speaker and steel, turn it on, and poke around with a chopstick and see what crackles......

Unless any of you don't advise that method!

Jim Eaton · Post by **Jim Eaton** » 2 May 2001 5:56 pm

Rob, if your going to take it out of the box,sent it off to John LeMay for a tune up.
He told me he rebuilt Buddy's Session 400 and that was all I needed to hear! Ya know!
I'm looking forward to getting mine back already and I just sent it off today!
JE:-)>

Mike Brown · Post by **Mike Brown** » 3 May 2001 5:23 am

Hello Rob,
Feel free to call me here at Peavey on our toll free line at 1-877-732-8391. I don't think that you will find anyone who will know the amp better than the designer/manufacturer.

We pride ourselves as being voted the number one manufacturer for the best service department in the MI industry. I look forward to speaking with you.

Thanks for using Peavey gear.

Mike Brown
Consumer Information Services

Rob Segal · Post by **Rob Segal** » 3 May 2001 4:53 pm

Jim, Mike thanks for your responses. I'm gonna look at it on the bench here at home, and then ship to Peavey if I can't find the problem.

Rob

Rob Segal · Post by **Rob Segal** » 4 May 2001 7:11 pm

It's fixed!!!!

I took out the chassis, connected it to speaker and steel and power, turned it on, and poked around, and sure enough, one of the 2 printed circuit boards showed sensitivity--became noisy and quie--as I moved it with the chopstick. Powered down, looked around, and saw that the circuit board is supported at its corners by small z shaped brackets, one leg of which is riveted to the chassis. These rivets were all loose, and the brackets turned freely. The circuit board was clearly using the brackets as a path to ground. Furthermore, the main ground from the power cable was made by another lug also riveted to the chassis, and also slightly loose.

So, I decided to fabricate a new ground lug, firmly bolted to the chassis, and connected to the above ground points by new ground wiring...and lo and behold it's dead quiet, and not knock/whack sensitive!

If anyone thinks I made a major technical error, please let me know. I suppose the better way to have gone about this would have been to replace all the rivets with nuts/bolts/lock washers, but they're a bit small and the hardware I have didn't lend itself to this solution...

So I'm feelin' kind of good, at least til it blows up and I have to send it to Mike Brown.

Rob Segal
NYC Session 400 tech.

Blake Hawkins · Post by **Blake Hawkins** » 5 May 2001 6:44 am

Good repair Rob!

Blake

Ken Fox · Post by **Ken Fox** » 20 May 2001 11:00 am

I'm right in the middle of restoring a 1976 Session. I checked the legs to ground, like yours, all 4 were completely loose!! Thanks for the suggestion, you probably saved me several days of hunting and pecking for a future intermittent problem.

Rob Segal · Post by **Rob Segal** » 21 May 2001 7:46 am

I suggest you also check the other riveted connections--there's one for the incoming 110v ac power cable's ground wire.

I'm glad this helped. My 400 is still dead quiet....

Rob