Posted by brian4561 (A) on April 24, 2007 at 22:30:15

I finished building my Foreplay III a week ago, and until today it was working quite well. Today, when I turned it on, I thought I saw a flash in the OD3 tube. I thought I imagined it, since the tube seemed to remain normally lit and, after all, it only had a week's use on it.

After about 3 minutes of music, though, this awful squealing started--like a feedback squeal. It was definitely in the Foreplay, as all of the other components sounded ok with it removed. Now that I've taken another look at the 0D3 tube, it is blackened on the inside.

Does anyone know what could have caused this? Did I get a bad 0D3 tube? Did something in the amp kill the tube? If its just the tube, thats an easy fix. I just don't want to get another tube, just to have it die on me right away.

• Re: Foreplay sqeals--bad tube? - josh 12:29:35 04/25/07 (0)
  In Reply to: Foreplay sqeals--bad tube? posted by brian4561 on April 24, 2007 at 22:30:15:

  I got the same sort of squeal when my output jack was grounding by accident.

  Josh
  
  

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• Re: Foreplay sqeals--bad tube? - Matts_ 11:16:45 04/25/07 (3)
  In Reply to: Foreplay sqeals--bad tube? posted by brian4561 on April 24, 2007 at 22:30:15:

  lotsa times a squealing is due to a bad ground connection somewhere- check all of them and make sure they're good hot solder joints. If one's bad it may get worse or change when you poke it (v. carefully) with a wooden chopstick or similar implement.
  
  

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  • Re: Foreplay sqeals--bad tube? - Doc B. 12:01:53 04/25/07 (2)
    In Reply to: Re: Foreplay sqeals--bad tube? posted by Matts_ on April 25, 2007 at 11:16:45:

    Yup, all true, and sometimes even more easy all you need to do is pull the tubes out and reseat them.
    
    

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    • Its working again - brian4561 16:51:49 04/25/07 (1)
      In Reply to: Re: Foreplay sqeals--bad tube? posted by Doc B. on April 25, 2007 at 12:01:53:

      And all I did was take the rectifier tube out, shake it up a bit and put it back in.

      I took it out and replaced it last night, but it still squealed. When I shook it, I heard something rattling around in there. Could the noise have been caused by a little piece of crud shorting connections inside of the tube itself?
      
      

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      • Re: Its working again - Matts_ 19:17:32 04/25/07 (0)
        In Reply to: Its working again posted by brian4561 on April 25, 2007 at 16:51:49:

        voltage reg tubes are very simple creatures- I doubt if anything would short it out that wouldn't have caused much more serious problems. It's also not too unusual to find little pieces of glass or insulator material inside tubes, and these are non-conducting. More likely just oxidation on the pins. If you feel energetic, take a good pencil eraser or a strong solvent (if you're chemically inclined) and give the pins a good cleaning. Have fun with it!
        
        

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• And about the 0D3 tube . . . - brian4561 23:04:13 04/24/07 (0)
  In Reply to: Foreplay sqeals--bad tube? posted by brian4561 on April 24, 2007 at 22:30:15:

  it was in an Ei box and had the Ei logo stamped on one side of the bakelite base. On the other side, the base was stamped "Marconi" and "Made in Canada."

  T thought that was kinda weird. Is that normal?
  
  

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