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Super Redhead hum issue

Discussion in 'Amps and Cabs [BG]' started by corsa, Jun 26, 2012.


  1. corsa

    corsa Supporting Member

    Jul 12, 2010
    Fort Wright, KY
    I have a Super Redhead that has started making an intermittent hum. This is not a cabinet buzz/rattle but a hum that changes volume when you tap the chassis.

    Originally, I believed it to be a ground issue because sometimes just touching one of the jacks would change the volume of the hum. Tapping on the chassis would always produce a result. Each tap would change the volume of the hum. Sometimes I could tap it away but often I couldn't. Also, this hum would sometimes announce itself with a loud crackle through the speakers. Ocassionally, the chassis tapping routine would elicit a crackle but usually not.

    So I took it to the shop. They re-flowed a bunch of ground connections and replaced a couple of bad plate load resistors. They ran it and pronounced it fixed.

    Well... it ain't fixed. It's much better but not fixed. Touching the jacks no longer has any effect but the hum still shows up. However, now it is at least predictable and appears to be initiated by chassis vibration. It can be brought on by the old chassis tap or by a loud note. It's not quite as loud as it was but it is still very annoying. The good news is that now, cycling the power will remove the noise until the next loud note.

    Anybody have any suggestions for a cause and solution for this issue?
     
  2. wvbass

    wvbass Supporting Member

    Mar 1, 2004
    West Virginia
    Did you replace the tube? Mine got noisy; a new tube was the fix.
     
  3. If you haven’t already - try it will a different bass and guitar cord.
     
  4. corsa

    corsa Supporting Member

    Jul 12, 2010
    Fort Wright, KY
    I should have mentioned earlier - I have tried three different (brand new) pre-amp tubes.

    Also used an active bass, a passive bass and no bass connected. Tried a couple different cables including a Mogami. No differences noted - the hum can be induced in any and all combinations of the above including when nothing is plugged in to the amp.
     
  5. seamonkey

    seamonkey

    Aug 6, 2004
    If you're up to it. Take it out of the case. Make sure all the screws and nuts are tight.

    Take out insurance. Get a plastic probe, like a bic pen with the guts removed. Turn it on and start tapping around. Push around on the wires and circuit board in case it still is a bad solder joint.
     
  6. CrashClint

    CrashClint I Play Bass therefore I Am

    Nov 15, 2005
    Wake Forest, NC
    DR Strings Dealer (local only)
    I had a problem with hum a few years ago on my Pre-Fender Redhead. The tech traced it down to the old DI. On older models the DI wasn't designed to handle phantom power from the board. SWR sent the upgrade parts to my tech for free and I think he charged me $65 to install the parts and hard solder all my grounds to the chassis.

    Except for the insurance, I tried what seamonkey recommended, before I had the tech look at the amp.

     
  7. corsa

    corsa Supporting Member

    Jul 12, 2010
    Fort Wright, KY
    UPDATE:

    After many weeks, I believe the Redhead is fixed.

    I took it back to the shop and demonstrated the problem and they agreed to work on it again.

    They had the amp for something like six weeks and had quite a story to tell when I picked it up. This shop is a tube amp shop and when the amp finally frustrated them, they hired a solid state tech and ended up paying him 50 bucks more than they charged me.

    The downside is that because of the multiple techs working on the amp and the long time frame, I don't know exactly what work was done. They mentioned that the circuit board looked to be hand-etched and that addressing one issue would frequently cause or expose another one. I know that they replaced a component in the power amp section but beyond that, all I know is that they said they addressed about a dozen different problems. They did assure me that the amp is still a spec Redhead - there were no substitutions or modifications made.

    The funny part is that, when I picked up the amp, I was able to induce the crack and hum by tapping the chassis again. After freaking out, the shop owner went through it with me one last time and we narrowed the issue to the unbalanced line out jack on the front panel. He pulled the chassis and worked on that jack and the problem was finally solved.

    The shop owner worked very hard on my amp and spent more than he charged me in the process. (I insisted he at least charge me another $50 so he would break even). He was great to work with but he did politely tell me that there was nothing more he could do for this amp and did not want to see it again.:) Though he did say he would refund my money if it wasn't fixed.

    This is the only story I've heard like this about a Super Redhead so I'm wondering if I was just unfortunate. Mine is pre-Fender according to a post I read by Hapa since it says that it was made in Sun Valley on the back panel.
     

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