I Almost Killed Myself (An Orange AD200B Story)

Discussion in 'Amps and Cabs [BG]' started by LowEndWooly, Oct 27, 2021.

  1. LowEndWooly


    Sep 3, 2013
    I just switched over from an ampeg tube rig to orange. (2 of the OBC115 cabs.. super nice). Got the amp from across the nation today. Power tube 2 had come loose and was rattling in the chassis when I unpacked it. I checked the tube and it actually looked good. placed it back in the socket and powered it on.. played well and sounded awesome. But then I took a look in the back and noticed that the #2 power tube was not warming up nor glowing like the rest. Stupidly.. very stupidly, I went to push it down to see if I could get it to work. BAM! I felt like there was an explosion in my head. I let out a slow and loud F bomb like I never have before. Honestly.. I'm just happy I didn't drop dead right there. And I'm not entirely sure why I didn't.

    Anyway.. I need some new tubes. I'm assuming its best to get a whole new power set and match them. Should I just go ahead and do the preamp tubes, too? Any recommendations on tube replacement?
  2. LowEndWooly


    Sep 3, 2013
    A pic of the two 115s for fun. D23D308B-65E4-4AAC-8BC8-382957E7C3C3.jpeg
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  3. Razman


    Feb 10, 2005
    Orange Park, FL
    The answer's obvious - you weren't wearing properly insulating footwear! Get some good, heavy duty boots the next time you want to mess around with tubes. :roflmao:

    All kidding aside, glad to hear you survived and are still on the right side of the grass. As for tubes, I have Groove Tubes in my Mesa 400, aside from that I'm not of much help.

  4. LowEndWooly


    Sep 3, 2013
    The contact point
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  5. LowEndWooly


    Sep 3, 2013
    The culprit
    816A1D66-C127-44DD-9E98-A6C65AE55036.jpeg A6C85D6E-CFF2-4359-B3D8-BCA2ED79A3D2.jpeg
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  6. LowEndWooly


    Sep 3, 2013
    Also.. while I wait on new tubes.. I read that you can run these with fewer power tubes but should keep them even.. So I should take out another power tube. Which positions should I leave open?
  7. JKos

    JKos Supporting Member

    Oct 26, 2010
    Torrance, CA
    Calling @agedhorse. Something doesn't seem quite right. You shouldn't get shocked just touching the tube.
    Last edited: Oct 27, 2021
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  8. If #2 is gone you can take out #4 one and it will run on 1+3.

    You will also need to move the impedance up so that would mean running a single 8ohm cab off the 4ohm output.

    Now that being said I would get a tech to look at this. Could just be a failed tube but it seems you may have had an arc and I would get that amp looked over before I started pulling out or swapping tubes.
    Last edited: Oct 27, 2021
  9. shnapper


    May 1, 2005
    Back in 1978 I was playing around on the roof of our house.. I accidentally touch the power line main with my right hand and the electric current pulled in my left hand and I become a human resistor. Try that for a zap, I luckily pulled myself away. I doubt you would have died if I survived the electric chair lol!!

  10. Killing Floor

    Killing Floor Supporting Member

    Feb 7, 2020
    Austin, TX
    That’s really the first time you dropped the F bomb? It’s my favorite word.
  11. Was it the metal tube retainer rather than the glass?
    I probly wouldn't be using it until it was 100 puh cent safe. And they're great amps, so I'd definitely be getting it 100%
  12. Ggaa

    Ggaa Supporting Member

    Nov 26, 2018
    I thought I had a loose tube and stupidly pushed up on it, it was hot as a motorcycle exhaust pipe, instant blister and probably an F bomb.
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  13. angelopbass

    angelopbass Supporting Member

    May 18, 2011
    struthers, ohio
    That’s exactly what I was thinking!!??
  14. LowEndWooly


    Sep 3, 2013

    So.. if I'm hearing you right.. don't run the two 115s while running 1/2 of the power tubes. Plug a single 8 ohm 115 into the 4 ohm plug?
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  15. LowEndWooly


    Sep 3, 2013
    With the explosion in my head, I probably fried a few neurons. I can't remember what happened exactly. It might have been the metal retainer that I touched.
    rodl2005 likes this.
  16. Wasnex


    Dec 25, 2011
    Not exactly sure what you are saying. Did you get shocked or did the amp make a super loud noise when you plugged the tube back in.

    Touching the spring retainer should not have shocked you. If it did, you need to get the amp checked. If you wiggled the tube in the socket the amp could possibly develop a flyback voltage that produces a bright flash of light from arcing in the tubes, and a loud sound like an explosion form your cabs. This happened to my Trace Elliot V-Type because the pins in the tube socket were not tight enough to make good contact.

    The V-Type did blow the mains fuse, but I opened it up, pulled the tubes, installed a new fuse, checked all the operating voltages and everything looked perfect. I retensioned the tube sockets, put the tubes back in, and brought the amp up on a variac. I am sure the tubes took a hit, but they biased up as they should and were still well matched. I got lucky as a really bad flyback can cause major damage.

    If you pull a pair of tubes it's a good idea to check the bias. When there are less tubes in the amp less current flows. With less current the power supply voltage goes up. More voltage will cause the remaining tubes to pull more current.

    My understanding is these amps are biased super cold from the factory (18-22mA per tube). This is under 50% dissipation. So it might be okay to simply pull two tubes...or maybe not.

    As @Plastalmonus suggest, removing half the output tubes doubles the expected impedance. So the 4 ohm output expect 8 ohms.

    It's generally not necessary to replace the small signal tubes every time you install new output tubes. The life rating of small signal tube can be 10,000hrs. Output tubes tend to wear out much faster, especially if you drive the amp hard.
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  17. LowEndWooly


    Sep 3, 2013
    yes, it shocked me, no noise (except for the explosion in my head). Really not sure how or why it did. So.. pulling the two power tubes.. should I still not run the amp at all then? Replacing the power tubes won’t cut it, you think I need to send it in regardless?
    Wasnex likes this.
  18. As a general rule I try to refrain from sticking my fingers inside powered up electrical appliances.
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  19. Wasnex


    Dec 25, 2011
    Here is what the circuit card looks like.

    The output tubes in this image are labeled 4-7 from right to left, so it looks like V5 is the tube you had a problem with.

    The schematic shows the V4 and V5 are connected to one side of the output transformer, and V6 and V7 are connected to the other side of the output transformer.

    If V4 is stops working, you can pull it and also pull either V6 or V7 (it doesn't matter which unless one of the fuses blows). However you may want to experiment to ensure the two remaining tubes are well matched. If one of them pulls significantly more current than the other, the amp will produce a hum that I describe as sort of a dull roar.

    The cathodes of the tubes are tied together in pairs and connected to ground via fuses. If a fuse opens, the associated pairs of tubes will stop conducting, and a LED on the the back panel will light. Two fuses/two LEDs (see the green circle below).


    Notice the labeling says 1+3 and 2+4. So the back panel labels the tubes inconsistently with the circuit board and schematic. Otherwise it would read 4+6 and 5+7. If a fuse blows, one tube on each side of the output transformer shuts off. That does not mean both tubes are bad, the amp shuts down the tubes this way so the current remains balanced in the OT as described above.

    The back panel also labels the fuses F500mA (fast blow). I believe the manual and schematic call for T500mA (slow blow).

    This stuff is sort of complicated and potentially dangerous. Not a bad idea to take the amp to a tech.
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  20. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Hmm... it's hard to be sure, but in the pictures the second tube from the left looks to me like it's rotated in the socket. Perhaps when the tube came loose and was rolling around, the key in the center of the tube broke off and when you inserted it, it was misaligned? I think the base shell is connected to pin 1 in some 6550s (that's what those are, right), and if that pin ended up where the plate or screen grid pin should be, you'd get 600 V or so on that metal shell.
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