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Ridiculous Tube Warmup Time (> 1 hr)

Discussion in 'Amp Central Station' started by jeff133, Nov 5, 2020.

  1. jeff133

    jeff133 TDPRI Member

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    Greetings, I'm new to tube amps. i have a small, cheap 5W (1 12AX7, 1 6V6GT) that's only about 18 months old. Initially I'd let it warm up for 10-15 minutes and it was great. Over time, it's been taking longer and longer to warm up. Even after 30 minutes, the volume is super low and the tone isn't right. Eventually (now taking well over an hour) the volume and normal tone kick in abruptly and from then on it's fine. Does this mean I already need to replace the tubes? Just the preamp, the poweramp, or both? Or is it likely something entirely different? I've been searching extensively and haven't come across this specific issue, so posing the question myself. Appreciate any assistance. Thanks.
     
  2. MilwMark

    MilwMark Doctor of Teleocity Ad Free Member

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    I don't know anything about amps but something has been "broken" since you got it if initially it took 10-15 minutes for the full volume to kick in.
     
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  3. Paul G.

    Paul G. Friend of Leo's

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    A tube is generally warm enough to pass current in about 40-90 seconds.

    Your amp is broken. It's apparently always been broken. Get it fixed.
     
  4. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    What amp is it?, does it have any sort of power reduction feature? ( which may be at fault, but it's unlikely ).
    One or two minutes tops for small valves to get to temperature. To take more than two minutes would indicate a dry or cracked solder joint to me. As the rest of the system heats up around it, contact is made and the amp works until it cools off. This issue gets worse over time as the joint is flexed and clearances widen.
     
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  5. Milspec

    Milspec Poster Extraordinaire

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    Even playing in a tent above the artic circle it wouldn't take that long to warm up....there is a problem with that amp.
     
  6. jeff133

    jeff133 TDPRI Member

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    i should have been more specific...i had read varying opinions on how long to let a tube amp warm up, so when i first bought it, i just started at 10-15 minutes (i'm an overly cautious person). it may have worked fine after 10 seconds, i just never tried it.
     
  7. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    I would bet there's a bad solder joint in the amp, but it definitely needs to see a tech.
     
  8. jeff133

    jeff133 TDPRI Member

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    Thanks. It's a Monoprice Stage Right 5W...as cheap as they come, so poor quality control would jive with your assessment of the issue. It does have a 1W / 5W switch, but the issue occurs with either setting. Appreciate your response though. Maybe I'll take it apart and try to check the solder connections and see if I get lucky (it's not worth the money it would cost to have someone fix it :)).
     
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  9. 68tele

    68tele Friend of Leo's

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    Maybe throw the tubes in the microwave for ten minutes on high - that should warm them right up.:twisted:
     
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  10. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    The Monoprice is based very closely on a Laney design, the Cub 8. Laney used what they refer to as a 'Polyswitch', which a resettable PTC device in the heater line just after the hum adjust pot. They were the weak point of the Cub series. They're through-hole, so easy enough to replace with either a wire link or a fuse. It's open to debate as to why Laney chose to fit it. They had a bad batch of them which led to a number of early life failures. Look for a rectangular yellow thing near the hum pot. It may be labelled 'F1' which confuses matters even more.
     
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  11. BelairPlayer

    BelairPlayer Tele-Afflicted

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    I find modern lead free solder to be garbage. JMHO. If you’re technically inclined and aware of the dangers of working in tube amps, I’d suggest reflowing solder joints with proper solder.
     
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  12. Wildeman

    Wildeman Tele-Meister

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    I let'em warm up for 10 or 15 seconds myself, never a problem in 30 years of tube amps. Don't over-think it. A lot of amps I've owned don't even have standby...
     
  13. jman72

    jman72 Tele-Afflicted

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    Yeah, more than 10-15 seconds is a bad sign. My 5f1 goes from nothing to max in about 10 seconds.
     
  14. jeff133

    jeff133 TDPRI Member

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    Well, I definitely was not aware of the dangers of working in tube amps, so I'm glad you mentioned that. If they can truly be dangerous even when unplugged, perhaps I should just get a cheap solid state and move on with my life.
     
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  15. jeff133

    jeff133 TDPRI Member

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    Thanks, this seems very helpful, but after the next guy's comment, we'll see if I decide it's worth looking into and trying myself. EIther way, thanks for the info!
     
  16. dan40

    dan40 Friend of Leo's

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    There can be 400v or more inside a tube amp even if it is unplugged. The larger capacitors inside can hold this voltage for quite awhile so it's always smart to check before touching anything.
     
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  17. JamesAM

    JamesAM Tele-Meister

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    Nothing wrong with that! Get a microcube! Those rolands are cool as heck.

    yeah the big capacitors In tube amps hold hundreds of volts of charge even unplugged- it’s what they’re designed to do. I’d skip that and see if you can find a tech to fix it if you really like the sound...or, alternatively, it sounds like there might be a NAD in your future!
     
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  18. W.L.Weller

    W.L.Weller Tele-Holic

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    @jeff133 was correct when he said it wasn't worth paying anyone else to work on a Monoprice amp.

    If you don't already own a soldering iron and have no particular interest in learning, definitely ditch the Monoprice amp (I bet you could get $20 on Craigslist).
     
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