The smell test

heiney9
heiney9 Posts: 25,165
edited September 2013 in The Clubhouse
Just looking for some opinions and experiences. I know eventually it will have to be sent in for service.

The last two times I fired up my Dared I-30 tube integrated after about 10-15 minutes of playing I smell something hot, not necessarily pungent burning type smell but something hot smelling and the left channel starts crackling and hissing. It uses (4) 6L6 GC power tubes 2 for each channel in a push/pull configuration. (2) 12AX7's and (2) 12AU7's for the input section.

Both times this has happened I have shut her down and after a few minutes of cooling down I start sniffing around seeing if I can smell a cooked component as well as doing a thorough visual inspection. No cooked smell or visual damage. Today I even took the back off and performed the smell test. Nothing smelled funky at all.

I suspect a bad 6L6 power tube. I need to roll another pair in the left side to see if that takes care of it. I should have done that today to rule out the power tubes, but it's already put away.

I know this is NOT the way to diagnose a problem. But I think there would be a cooked smell inside the amp if something was toast.

What do you think?

H9
"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • george daniel
    george daniel Posts: 12,096
    edited September 2013
    Can you look at the resistors/caps by pulling the bottom plate? I'm guessing by your post that it does not smell like toobs due-- you know,, that tooby smell? Good luck--let us know.
    JC approves....he told me so. (F-1 nut)
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    I did pull the bottom plate George, looks like new, smells like new.

    No not the typical hottish metallic smell of fully warmed up power tubes. It's definitely a hot burning smell, just not a putrid smell. Almost similar to melting plastic, I guess. Maybe a cross between a card board box burning with a hint of hot plastic. The tube sockets are ceramic. It's also a self biasing unit, not manual.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • george daniel
    george daniel Posts: 12,096
    edited September 2013
    Can you test the tubes? I had a tube that kinda exhibited the same symptoms as you are having-- turns out it was a bad plate to ground issue with the tube IIRC--good luck!
    JC approves....he told me so. (F-1 nut)
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  • Msabot1
    Msabot1 Posts: 2,098
    edited September 2013
    Maybe a transformer fixing to take a dump? Happend to me,clue was the crackling noise you spoke of...they kind of smell at first and when they go it stinks bad...just a thought.
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    No way to test other than rolling in another pair. Maybe I'll put the original Ruby's in and see what happens.

    I did cook a tube once on my other unit which is manual bias. Didn't realize until after I cooked a nice 50's RCA 6V6 that is was 50ma higher current on that tube than was called for. :eek:. It exhibited the sound characteristics of this unit, don't remember if it smelled.

    My other reasoning is if it was a bad component it should react right on start up, not after being run for 15 minutes, which ironically seems to be when the power tubes reach temp.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    I guess the next logical step is to try different power tubes. If the problem still exists then it's time to send her in.

    I was just thinking outside the box with the smell test and looking for some discussion. Keep it coming.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    Msabot1 wrote: »
    Maybe a transformer fixing to take a dump? Happend to me,clue was the crackling noise you spoke of...they kind of smell at first and when they go it stinks bad...just a thought.

    Tranny case is stone cold. You could be right. This was brand new when I bought it. If it has 25 hours on it, I'd be surprised.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • SCompRacer
    SCompRacer Posts: 8,496
    edited September 2013
    I’ve seen transformers that contain wax to prevent hum from windings vibrating. The wax can melt if temps get hot enough inside which means something is causing the PS tranny to get that hot. If a wax filled transformer gets hot enough, it will leave traces like poo piles under it and the odor remains. But you say the trannys are not hot.
    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
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  • Rivrrat
    Rivrrat Posts: 2,101
    edited September 2013
    While I've never had to use the smell test on audio components, I've used it on telcom circuit cards with pretty good success. It sounds to me like you've used it as far as it'll go and now it's time to change out the suspected culprit.
    My equipment sig felt inadequate and deleted itself.
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  • megasat16
    megasat16 Posts: 3,521
    edited September 2013
    Sniff, visual, temperature sensing with hands (no touching on ac parts, cables, wires, transformers, capacitors, tubes or transistors) is usually the first step I do with all electronics problem.

    But like everyone else have already said, I would just replace the offending toobs and see if it go away. If it doesn't, look for the crack in the tube sockets underneath or clean the sockets with electronics cleaner.

    If you do roll toobs often as you are, tube sockets could probably be lose or dirty or have a micro crack somewhere.

    If the other parts involved, you really need a meter and a schema to start looking for the offender.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • treitz3
    treitz3 Posts: 19,015
    edited September 2013
    My guess would be that you have a bad tube in the mix somewhere and it's roasting a resistor beyond medium rare.

    Tom
    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
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  • headrott
    headrott Posts: 5,496
    edited September 2013
    treitz3 wrote: »
    My guess would be that you have a bad tube in the mix somewhere and it's roasting a resistor beyond medium rare.

    Tom

    This was my first thought as well. I think you are smelling the resistor, but a tube is causing it to "cook".
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • Dawgfish
    Dawgfish Posts: 2,554
    edited September 2013
    ^^+2^^
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    Ok, so I finally had some time to spend swapping in different power tubes on the offending channel. So far so good! Must be a bad tube out of the pair on the left side. Thanks for the help in troubleshooting. I sort of had a feeling it wasn't the gear.

    Now does anyone have a tube tester to test 6L6GC's to see which of the two is the bad one. I hate to figure it out in amp, as I don't want to do damage.

    Thanks

    H9

    P.s. The office rig sound fantastic!
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • nikolas812
    nikolas812 Posts: 2,915
    edited September 2013
    I thought this thread was going to be about panties. :/
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  • Msabot1
    Msabot1 Posts: 2,098
    edited September 2013
    Naa...not so lucky....glad it wasn't a trans...
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  • headrott
    headrott Posts: 5,496
    edited September 2013
    heiney9 wrote: »
    Ok, so I finally had some time to spend swapping in different power tubes on the offending channel. So far so good! Must be a bad tube out of the pair on the left side. Thanks for the help in troubleshooting. I sort of had a feeling it wasn't the gear.

    Now does anyone have a tube tester to test 6L6GC's to see which of the two is the bad one. I hate to figure it out in amp, as I don't want to do damage.

    Thanks

    H9

    P.s. The office rig sound fantastic!

    Glad you got it figured out Brock. No "overdone" resistors though, huh? That's good news. My brother might have a tube tester that can test 6L6GC's. I don't remember for sure, I can ask him.
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • tonyb
    tonyb Posts: 32,958
    edited September 2013
    nikolas812 wrote: »
    I thought this thread was going to be about panties. :/

    Ya know.....you and I think a lot. Smell test ?? Last time I used that was in High School. Then I saw it was Brock who posted and figured he just had a smelly sock left behind the gear rack.
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  • SCompRacer
    SCompRacer Posts: 8,496
    edited September 2013
    tonyb wrote: »
    Ya know.....you and I think a lot. Smell test ?? Last time I used that was in High School. Then I saw it was Brock who posted and figured he just had a smelly sock left behind the gear rack.

    I'm thinkin' you and Nik maybe has a wore out Sept 93 issue of Hustler....the S & S page....:eek::cheesygrin:
    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
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  • heiney9
    heiney9 Posts: 25,165
    edited September 2013
    headrott wrote: »
    Glad you got it figured out Brock. No "overdone" resistors though, huh? That's good news. My brother might have a tube tester that can test 6L6GC's. I don't remember for sure, I can ask him.

    The resistors look and smell :cheesygrin: fine. I shut it down both times as soon as I smelled that smell. I ran it yesterday for a couple hours with zero issues. It does have fuses so I;m not sure if it got real bad if the fuses would have eventually popped or not.

    Yeah, check with your brother, I just want to eliminate the bad one.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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