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HELP! Strange Sounds from my WT400

Discussion in 'Amps and Cabs [BG]' started by jive1, Nov 29, 2003.

  1. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Owner/Retailer: Jive Sound
    My Eden WT400 isn't working right. I have changed the tube, tried different cabs as well as headphones, checked cables, and the thing is still giving me problems.
    This is what is happening: It appears that the bass control doesn't work. The treble and master seem to both control the master volume. If the treble is down and the master volume is up there is no sound. If I crank up the treble, volume seems to come back. After about 3-5 minutes some strange sounds come out of the amp. It sounds like wind blowing or a plan taking off, and there's a few other odd sounds like frequency modulation. The noises start out quietly and then get louder and louder until the signal from my bass cuts out, and all I hear is the noise. After a few more minutes the amp shuts down. During this time the EQ clipping lights goes on and stays on until the amp cools down. It sounds like the amp is haunted.
    Right now the bass amp is not usable to me. It won't work for more than 5 minutes regardless of what bass or cabinets/headphones I use. So if anyone can help, I'd appreciate it.

    Thanks in advance.
  2. T. Brookins

    T. Brookins Supporting Member

    First of all, I think you have good taste! The Fortress is one of Warwick's tastiest models.

    What were your gain and master settings on this amp?

    I had only minute problems with the treble control. Sometimes the boost was inconsistent. The problem vanished after a few days. I never really used the treble sheving control anyway. After a new tube, The problem was completely gone. Since, I've kept the insides and the pots clean, I haven't had any problems. It sounds to me like a problem with the preamp voltage interacting with the power amp. Trippy! I don't know what's going on. It sounds like the preamp is where your problem originated. What tube did you use? Is it well seated? Is every contact solid?

    Do you use the compressor alot? Resistors, diodes and capacitors are cheap, easily replaceable, and are most likely the problem. When these are the problem, usually there is no sound. Are you familiar with the inside of this amp?

    Bad tube maybe?

    Try first to plug your bass into the effects loop RETURN. I was told that this bypasses the tube, compressor, and enhance circuit. If that doesn't work, then
    -Plug your bass into the AUX IN pach in the rear. Does it work? Here, you are bypassing the preamp.
    If all is normal, then it is a complete preamp problem.

    Do these noises occur when nothing is plugged in? Interference? Are you playing through a speaker cable? The reason, I believe, why the power amp shuts down is that the pre stage could be sending a strange or subsonic signal to the power amp causing it to overheat- and oscillate? are the interconnects between internal components solid?

    Good luck, my WT-400, GS-112 playing brother.
    An Awesome, adequate combination.
  3. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Owner/Retailer: Jive Sound

    Gain and master on midway is what I test on. The problem occurs regardless of setting.

    I used a 12AX7 tube. A Mesa and a Sovtek. Problem occured with all tubes. They are well seated.
    The problem is definitely with the preamp. The problem occurs if there is no sound going into the amp after some time. If I disconnect the preamp, the problem disappears.

    Not a bad tube. The problem occurs regardless of whether the compressor is on or off.

    Problem occurs regardless of input (AUX IN, RETURN, INPUT)

    The problem will occur with nothing plugged in. Not playing through a speaker cable. I have noticed some white blocks are heating up on the preamp circuit board. I don't know for sure if ALL interconnects are solid. What I have noticed is that if I push the Bass knob up against the chassis (forming a hard contact between the pot shaft and the chassis), and put the bass knob set to 10-20% (until I hear a pop), the problem goes away. The bass knob will still cause the problem to occur if I crank it past that point, or if the contact between the chassis and the pot shaft is slightly broken. It really is a strange problem, and the saddest thing is that it renders the sweet sounding Eden useless.

    Thanks. I really want to get this thing working.
  4. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    Do the bass pot's legs have a solid connection to the circuit board?
  5. T. Brookins

    T. Brookins Supporting Member

    Those white clay resistors, I think, run hot normally. Mine do. The ones sitting right behind the "Traveler" logo, by the power switch usually warm the front panel by the end of a gig. I wouldn't worry about those.

    Ixhulu had a point. More than likely, the pots could be to blame. If you don't see any burnt resistors or frayed wires, The pots are definitely worth testing.

    When I had a smaller problem, i just cleaned the pots and retouched a few solder joints.

    You seem like a tasteful, knowledgeable WT-400 owner. I hope things go well for you.

    More peculiar info?

    I'll be posted.

  6. T. Brookins

    T. Brookins Supporting Member

    Oooh. It sounds like just a pot grounding thing.

    What you said about the pot shaft and the chassis leads me to believe that the pot solder joints are just loose and need reheating.

    Yeah, keep your pots tight so they don't pull at the solder joints.

  7. gfab333


    Mar 22, 2000
    Honolulu, Hawaii

    Fellow Eden head owner here. I think that you and Tbrookins are doing a great job troubleshooting your amp.

    One other suggestions is to have David N., or his techs, review this thread. he may be able to help you.

    Last week, I used the "email us" link at the Eden website to pose a question on overdriving the tube preamp, nothing urgent like your problem. I expected some underling tech person to email me back three days later. But you know what? Mr. David responded to me himself the very next day! That's great customer service.

    Here's the email address...

  8. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Owner/Retailer: Jive Sound
    Thanks for the help guys!

    I sent an e-mail to Eden and shared some the trouble shooting that has been going on so far , and hopefully they'll have some insight into this.

    I tried to replace the pot on the bass, and it didn't do anything. Can a different pot cause this problem other than the bass pot? Reason why I am saying this is because this is the pot that really seems to affect the problem. As stated earlier, if has a hard ocntact with the chassis and is set to somewhere between 10-20% the problem goes away, but the pot still doesn't work. Another thing to note is that I can hear buzzing from the amp depending on which pot shaft I touch, and the setting (or grounding?) of the bass pot.
    Can just a dirty potientometer cause a problem like this? I know they can cuase scratchy sounds when turning, but a complete preamp breakdown?
  9. Sounds to me like you have a capacitor issue some where. I've been told that the electrolytic caps have been known to 'dry out' over time, then they fail. It could be causing an ultrasonic oscillation that is over loading the power amp, and you wouldn't be able to hear that but the amp would feel it (ouch). If you changed the bass pot and you are having the same problems it's very unlikely that it's the pot. But check the caps around it for funky solder joints. The input jack on my WT-300 was all messed up when I got it. It has some other issues too, also in the preamp but not as spooky as yours. It tends to distort at very low levels - preamp gain at 10:00 or so. But alas, very little time to work on it.

    Sounds like a trip to the tech might be in order.

    p.s. Nice Warwick. The Fortress is the only warwick I ever liked the look of. Too bad they quit making them.
  10. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Owner/Retailer: Jive Sound
    Well, I went out and bought some contact cleaner and a multimeter. I can't believe I never owned a MM before. Shame on me for not making my life easier. Anyways, I did find that the bass potentiometer was bad. And the one I tried to replace it with was bad too. So I went out and bought a pot from Guitar Center. They only had 500K dime size pots, so I went with a 500 instead of a 100 which is what the Eden originally had. I tested the pot, so I felt safe in proceeding. Since it was a pot for a guitar instead of a PC board, I had to file down the contacts so it would fit into the circuit board. Then I had to file down the pot shaft so it would fit into the chassis. Sheesh, what a pain. After soldering the new pot into the board, and plugging everything back in, I was ready to test things out.

    I played my bass through it for about 20 minutes through headphones and speaker cabs and the mysterious sound did not appear. The bass knob works too. The only thing is that it seems that 1-50% is same, and that bass is brought up somewhere between 60-80%, with a significant boost after that. The pot shaft barely fits enough out of the chasis to stick a knob on it, but I can't put a nut on it to secure it since I filed down the threads to get the thing to fit in the first place. Anyway, I think the problem is solved. Time will confirm.

    Thanks to everyone who helped out on this one. I'm loving my Eden tone!
  11. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    Cool Beans. Don't forget to replace the pot with the real deal somewhere down the line.
  12. That's about what I'd expect with the wrong pot in there. It won't do any harm, but get on the line with Eden and they will sell you a new one.

    Or the local Radio Shack might have something that would work too. The ones I've purchased there have plenty of shaft length too.