79 Vibro Champ issues.

Discussion in 'Amp Tech Center' started by jwp2, Feb 17, 2020.

  1. jwp2

    jwp2 Tele-Holic

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    Hello everyone!
    So today I fired up my Vibro Champ and after a few seconds, it blew the fuse. I replaced it with another one, pulled the tubes and turned it back on. The jewel stayed lit and the new fuse didn’t blow. As I replaced the tubes one by one, all tubes had power except the 6v6 power tube. I had a known to be good tube I tried and it was dead. So, no power to the power tube socket.
    It’s sure looking like tech time, but what do you all think it could be?
    Thanks in advance.
     
  2. Jon Snell

    Jon Snell Tele-Meister

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    Did the 6V6 damage the 5Y3 rectifier I wonder.
    At this point you will need to get your multi-meter out, observe all safety notifications and measure the HT from the 5Y3 and do some fault finding.
    Mostly the mains fuse blows because either the 6V6 flashes over or the 5Y3 fails but sometimes if the incorrect valued fuse is used the transformer can suffer.
    It is not usually caused by HT smoothing capacitors.
    If you are not competent as a technician, I would advise consulting someone who can do the job for you.
    Have fun and be safe!
     
  3. Wally

    Wally Telefied Ad Free Member

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    If you are saying that the 6V6 heater filament is not glowing, it is odd that just that tube has lost its heater filament supply because it is in a chain of supply that feeds the two 12AX7s as well. There could possibly be a situation whereby that supply chain is uninterrupted but the socket for the 6V6 has a problem with either pin 2 or pin 7. Tech time regardless if you don’t do your own work.
     
  4. jwp2

    jwp2 Tele-Holic

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    Good morning guys. Yes, I had a spares 6v6 as well as a spare 6L6 both known to be good. No power with either tubes, meaning neither heater filament would glow. Meanwhile both 12Ax7s and the rectifier tube where glowing hot.
    I’ll take it to a tech soon.
    Thanks for the responses!
     
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  5. muchxs

    muchxs Doctor of Teleocity

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    It's not really odd. I forgot for a moment stock Champs pick up one side of their filaments from the ground. 6V6 won't light? That's easy! I'll bet the filament connection lifted from the chassis.

    I had a "Friday Afternoon" Princeton Reverb over here a while ago. I was able to lift most of the chassis grounds with my thumb nail.

    The bad news is the OP needs something like my WMD soldering iron for his Amp Dungeon. WMD must be 500 watts. It makes quick work of those pesky chassis grounds.

    The OP could run a jumper to the grounded side of the pilot light. It ain't pretty but it will work.

    OP, don't mess around in there if you don't know what you're doing. You could nuke your PT if you short your filaments.
     
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  6. Wally

    Wally Telefied Ad Free Member

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    I forgot about one side of that supply being grounded in these little Fenders, muchxs....thanks.
     
  7. jwp2

    jwp2 Tele-Holic

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    B9CF8C07-179C-4BC9-B920-FAC839116C87.jpeg 454D3849-B0D1-430A-9CB2-4A39C5EE32D7.jpeg
     
  8. jwp2

    jwp2 Tele-Holic

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    Here are some proverbial gut shots.
     
  9. Wally

    Wally Telefied Ad Free Member

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    Well, you have it open. If you have a meter, you can find where that heater filament supply is failing for that 6V6.
     
  10. Whatizitman

    Whatizitman Friend of Leo's

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    Well, whoever recapped it used whatever cheap stuff they had on hand. Have someone knowledgeable fix it. Could be just a bad solder on the output tube socket(?)

    EDIT: OP, you have several of TDPRI's most knowledgeable amp folks on this thread. They will steer you in the right direction.

    My question to all: does the soldering on the grounded filament leg at the socket look a little black? Cold solder, broken, or something arced, perhaps? Something looks funky, but I can't see close enough to tell.
     
    Last edited: Feb 18, 2020
  11. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Turn it on, wiggle the green wires to the tube sockets carefully and lightly. Snap crackle pop?
     
  12. Wally

    Wally Telefied Ad Free Member

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    fwiw, those heater filament wires are very light green, aren’t they? As for the recap job, I would have to see the codes 9n that multi section cap can there to be sure that that is not original to the amp. The filter caps need to be changed, I think......I don’t see evidence that anyone has replaced that can. I could be mistaken....I am a long way fr9m the amp. jwp2, what are the codes 9n that can?
     
  13. jwp2

    jwp2 Tele-Holic

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    Hey guys, thanks again for the responses, no snap crackle or pop when wiggling wires to the tube sockets.
     
  14. jwp2

    jwp2 Tele-Holic

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    56625F4B-E17E-436F-8F13-1478A9081DD4.jpeg
     
  15. jwp2

    jwp2 Tele-Holic

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    Here’s the only info on the cap can.
     
  16. jwp2

    jwp2 Tele-Holic

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    I know these guys are the best of the best. I really appreciate the willingness to help out. You guys rock!
     
  17. Whatizitman

    Whatizitman Friend of Leo's

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    Observe all high voltage safety precautions, if you haven't already. Use a chopstick to probe, or the wood side of a pencil. Only one hand in the chassis at any time the amp is on.

    Tube in or out? Speaker plugged in? Anyway, if no power is getting to the socket, I assume there there will be no sound. With the amp off (AND FILTER CAN CAPS DISCHARGED!!!!!), is the little leg on the 6V6 socket (pin 7) that is soldered to the chassis loose at all? That's the grounded side of the filament - what muchxs was referring to. That shouldn't move.

    EDIT: in other words, if the tube is not heating, you won't hear cracks and pops. If for example, probing a bad solder on the filament wiring makes a connection, the cathode will still need time to heat.

    Someone please correct me if I'm wrong on this.
     
    Last edited: Feb 18, 2020
  18. muchxs

    muchxs Doctor of Teleocity

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    I can't see much in the pics.

    What we're looking for is the littlebare braid that comes off the 6V6 Pin 7 behind the foot swtich jack. It should have a good connection to that blob of solder on the chassis.

    If the 6V6 isn't lighting and the 12AX7s are that's about the only thing it can be.

    ...unless the reference pin is broken off the 6V6.
     
  19. jwp2

    jwp2 Tele-Holic

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    Ah, snap crackle pop through the speaker. I was thinking you
    Meant like a wire arching.
    There is no ground from the 6v6 tube socket to the chassis. In fact nothing from the power tube socket is soldered to the chassis. Perhaps it’s grounded through another connection?
     
  20. jwp2

    jwp2 Tele-Holic

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    Muchxs, there isn’t any braided wire coming from the 6v6 tube socket.
     
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