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Need Help Troubleshooting '66 Ampeg B18N Issue

Discussion in 'Amps and Cabs [BG]' started by OldFenderPlayer, Feb 13, 2016.

  1. So I turn on my 1966 Ampeg B18N to do some practicing today, but instead of nice warm, round tone, I get a very distorted sound. I immediately turn it off and unplug it from the wall. I played it a few days ago and it was fine.

    Would this likely be a tube or some other electric part going back? Or could the speaker fail because of age?

    To add insult to injury, my trusted tube amp technician closed shop late last year, and I haven't used the new guy here in Richmond, Virginia.

  2. Is yours with tube rectifier or SS rectifiers? Could be a faulty tube in the signal chain. @beans-on-toast could have many more ideas.
  3. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    There are many possibilities and it isn't necessarily an expensive fix. As was mentioned, the first thing to check is the tubes. Reseat each one in turn, pull it and reinsert it, check that the wires running to the speaker inside the cab are firmly connected, check the power cord at both ends. Try the amp again. Otherwise, it looks like the tech should take a look at it.

    I doubt that the speaker would suddenly fail if it was fine the last time that you used it. If it is a tube, with a fuzzy distortion, chances are it is a bad rectifier tube (as B-string said, some B18's are solid state), the 7199 phase inverter, or a power tube. If you have a 5AR4/ G34 rectifier tube in another amp you can try it. A rectifier tubes is basically two diodes, if one diode goes, the amp can distort as you described. On the other hand, it could be a bad cap or other component.
    OldFenderPlayer likes this.

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