'65 BF Twin Reverb - pulled V1 tube, killed amp

Discussion in 'Amp Tech Center' started by Tone Fiend, Sep 8, 2015.

  1. Tone Fiend

    Tone Fiend TDPRI Member

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    Good afternoon, I hope you're all doing very well today. I'm a long-term lurker here at TDPRI, & I value your thoughts & opinions.

    So I pulled V1 preamp tube (channel 1's preamp) in my twin as I've done many times before (i only use the vibrato channel), plugged my guitar back in & turned 'er on, now my beloved amp refuses to power up. I immediately turned the power off, plugged the tube back in & then turned the power back on, but she's not even trying to fire up.

    Any ideas as to what might be going on?

    Thanks in advance for any & all ideas/help!
     
  2. John Owen

    John Owen Tele-Afflicted Ad Free Member

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    I assume you checked the fuse?
     
  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Have you checked the amp's fuse?

    If the fuse is ok are the tubes warming up and glowing like usual?
     
  4. clintj

    clintj Friend of Leo's

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    I'm assuming this is an original, not a reissue?

    With the tube out, a socket pin may have leaned over and shorted to another one inside. Check the fuse, replace it if needed, and see if it powers up. Fingers crossed it didn't short plate voltage to the heater circuit and damage the winding.
     
  5. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Chances are pulling the V1 tube had nothing to do with the power failure.

    Powering a vintage amp up is when the most failures occur - normally when the standby is flipped after warmup, but it's not uncommon for a failure to occur hen the power switch alone is turned on.

    Obviously, as previously mentioned, the fuse is the first thing to check. IF nothing is lighting up - are you saying there is no pilot, no filaments lighting - or things are lighting up but there's no sound?

    Either way - how long since the amp has been serviced, and what was done then? If it's never been serviced that you are aware of just take to a qualified tech right away.
     
  6. Tone Fiend

    Tone Fiend TDPRI Member

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    1st, thanks for the questions/suggestions & interest in helping. You guys are great - It's not blowing fuses, nothing is lighting up at all, & it just refuses to power up. It's vintage, & it was last serviced about 4yrs ago by my local tech. He installed new tubes & caps, a 3-prong power cord, & said she was good to go. It still had the original tubes, which I have, & speakers. I've played it daily since last service & have only had a slight crackling noise when adjusting Chan 2 volume.
     
  7. bparnell57

    bparnell57 Poster Extraordinaire

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    Could be a bad power switch. Odd coincidence if it is. Have you tried turning it on with the tube put back in?
     
  8. Fred Mertz

    Fred Mertz Tele-Afflicted

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    Have you tried a different wall outlet? Maybe a breaker tripped.
     
  9. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    What you got there is a mysterious mystery. Time to get out the volt meter and start figuring out where the voltage stops. **Note: only do this if you know how not to kill yourself working on an amp.**

    You said it's not blowing fuses. Did you remove the amp's fuse and test it, or replace it with a known good one? That's the most common point of failure. A bad power switch is not unheard of, but not especially common, either.
     
  10. Tone Fiend

    Tone Fiend TDPRI Member

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    Yes, I've tried powering up with the tube back in... still nothing.
     
  11. Tone Fiend

    Tone Fiend TDPRI Member

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    yes sir, ive also tried different outlets, including those in which other amps work just fine ;/
     
  12. Tone Fiend

    Tone Fiend TDPRI Member

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    I enjoy a good mystery... not sure how enjoyable this one's gonna be. I did pull the old fuse, which wasn't blown, & replaced it with a new one.. still no juice.
    I do know how to not kill myself inside these amps, but I'm definitely not an expert. I'm not afraid to try, though. Hey, I don't want to go now, but if I had to, working on an amp wouldn't be the worst route.
    I'm going to bust out the volt meter & get to testing.
    I'd just been playing when it went out; I unplugged it & let it sit for about 15mins,pulled V1, plugged it back in, flipped the stand-by switch, NADA. Unplugged, made sure my power cord connection was good, plugged back in, hit power on, NADA. Repeat, put V1 back in, NADA. Like I said, I've pulled that tube before (many, many times) & have never had an issue. what a bummer
     
  13. clintj

    clintj Friend of Leo's

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    Give it a good once over with your nose. Anything catastrophic like a burned resistor or transformer winding, or blown cap, puts out a nasty, distinctive aroma.

    A complete refusal to power up, coupled with not blowing the fuse, is worrisome though. I like Fred's idea - check the outlet for power first before you get into the chassis. You might have tripped a GFCI if your outlets are supplied by one. It only takes a few mA of leakage to ground to trip one.
     
  14. soulman969

    soulman969 Telefied Ad Free Member

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    '65 BF Twin Reverb - pulled V1 tube, killed amp


    I'm sure it wasn't intentional on your part. A good attorney can probably get you off with charge of amp-slaughter. ;)

    It does sound pretty damn strange though and probably not related to the tube at all. Sounds more like some component just reached the end of it's useful life and up and quit. It's a 50 year old amp and that does happen.
     
  15. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Multimeter troubleshooting:

    Do the power switch terminals (both) have AC wall voltage when the power switch in ON? Does the fuse have the same voltage on both terminals?

    If yes:

    Is there high voltage AC from the power transformer at the rectifier tube? Is there 5v AC on the rectifier heater wires from the power transformer? Is there 6.3v AC at the heater wires at the first power tube and the last preamp tube?

    If yes:
    Is there high voltage DC at the big filter caps?

    If yes:
    Record all the DC voltages on all the tubes and post it here.
     
  16. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    I just came to check the thread and was going to say just about exactly what rob said.
     
  17. Wally

    Wally Telefied Ad Free Member

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    It is good to know how not to kill oneself in there. Have you taken measurements of live voltage before? Do you know where to check for that AC input voltage? Do you know where the rectifier circuit is....since there is no rectifier tube? Do you recognize the heater circuit? Do you know the tube pin outs so as to be able to take voltage measurements there? Have you studied a layout...and/or a schematic? Have you read some tube amp repair/maintenance literature?
    I am a cautious sort....so I have to ask these questions. However....learning is...no matter your level of experience or understanding, it is your world there. One hand behind the back...one hand behind the back. A shock with one hand in contact with the voltage can hurt. A shock with both hands involved can kill. Don't ask how I know....I don't have nine lives left...even though I am one cool cat!! LOL
     
  18. Tone Fiend

    Tone Fiend TDPRI Member

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    Good morning,

    I busted out the multimeter & got ready to give her a thorough going over.. figured it couldn't hurt to plug in & try to power up 1 last time. same outlet w/ V1 in, hit the switch, & there shown the most beautiful red ruby light I've ever seen! Turned it back off, pinched myself, back on, VICTORY! Pulled V1 back out, pulled V6 (12AU7 phase inverter) & replaced w/ V1. Power on, good to go. Plugged in the old LP, & who the hell knew I could get growl like that out of a Twin?! I absolutely love it.

    Thanks to everyone who commented, & even more to those who took time to give detailed instruction. KokoTele, Robrob, clintj, soulman969 - you guys are incredible. Thank you so much for your time & consideration.
    Now, is there anything more I should do to ensure nothing crazy happens as a result of this mod? Also, if you guys have other tips as to how I can make this beauty growl even more, I'd love to hear them.

    Thanks again, & good vibes to each of you -
    T OVER & OUT
     
  19. Tone Fiend

    Tone Fiend TDPRI Member

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    LOL - from one cool cat to another, Wally, thanks man!
     
  20. Fred Mertz

    Fred Mertz Tele-Afflicted

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    V1 is not your problem IMO. The symptoms point to an intermittent connection in the power supply. It could be dirty connectors in the On/Off switch or a bad switch as bparnell57 suggested or a bad power chord.
     
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