Tweed Bassman - Burning smell

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shaunmshaunm Frets: 1591
I could use a bit of forum wisdom.

I was using my Tweed Bassman Ltd 59 tonight and it started to emit a burning smell, actually the smell got that strong I had to turn the amp off and leave it alone.

Now it has been a while since I’ve beem able to use the amp Where the volume was on 7 but I shouldn’t have thought that was problematic?

Are these Bassman amps prone to this?

Full disclosure - whoever owned it before me has had some sort of master volume fitted to the back of it. I haven’t used it as I think it sounds rubbish.

The amp does hum more than my other amps which I am guessing would indicate some sort of problem? 

Any words of of wisdom from the usual suspects @ICBM @Modulus_Amps @Van_Hayden @RiftAmps ;
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Comments

  • TheMarlinTheMarlin Frets: 7746
    That’s the smell of ‘tone’, baby!
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  • shaunmshaunm Frets: 1591
    TheMarlin said:
    That’s the smell of ‘tone’, baby!
    It did sound good.

    it smelt like a pending electrical fire though
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  • Modulus_AmpsModulus_Amps Frets: 2570
    tFB Trader
    Shaun, take it to a tech and don't use it, the new bassmans have fuses in multiple place that should protect it, but it is possible that they have been replaced by an idiot.

    Burning smells come from something burning, hopefully it i just a cooking mouse and not a cooking transformer
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  • ICBMICBM Frets: 71963
    Shaun, take it to a tech and don't use it, the new bassmans have fuses in multiple place that should protect it, but it is possible that they have been replaced by an idiot.

    Burning smells come from something burning, hopefully it i just a cooking mouse and not a cooking transformer
    This. Actually the fusing in modern Fenders is best described as obtuse...

    This is the result of their decision to use a filament fuse and not an HT fuse in a very expensive Custom Shop amp. Neither the filament nor the mains fuse had blown.





    ... but the ceramic valve socket got so hot that it burnt the chrome plating on the amp chassis white, as well as melting the wiring. Caused by a valve base burning that left enough carbon on the socket to make it arc.

    Don't risk it.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • shaunmshaunm Frets: 1591
    Thank you gents,

    I am booking it in with a tech. Can I ask you what would possibly cause a transformer to heat up to the point of burning up? 

    I am wondering if the person who put in the master volume mod did a hack job?
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  • jpfampsjpfamps Frets: 2724
    edited December 2018
    shaunm said:
    Thank you gents,

    I am booking it in with a tech. Can I ask you what would possibly cause a transformer to heat up to the point of burning up? 

    I am wondering if the person who put in the master volume mod did a hack job?
    MV mod should not have caused any over heating problems.

    Even the Custom Shop amps I've seen are wired for EU 230V AC rather than UK 240 AC, and this will cause the transformer to run hotter.

    Fender also used to shop their 6L6 loaded Custom Shop amps with their "premium" GT 6L6-GE. In my experience these are the most unreliable 6L6s on the market.

    I've had several sets of these expire straight out of the box.

    Hum is often caused by imbalance in the power valves.
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  • shaunmshaunm Frets: 1591
    Thank you @jpfamps what you have said there is an exact echo of what the tech I am taking it to have said ( Howard of MAC amps Leeds). 

    Interesting really as it would seem that these amps are almost made to fail or work not as well as they can deliberately?  
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  • jpfampsjpfamps Frets: 2724
    shaunm said:
    Thank you @jpfamps what you have said there is an exact echo of what the tech I am taking it to have said ( Howard of MAC amps Leeds). 

    Interesting really as it would seem that these amps are almost made to fail or work not as well as they can deliberately?  

    I don't think that these amps are "made to fail"; Fender amps are in my experience generally very reliable.

    Modern valves are usually the source of most of the problems in valve amps.

    6L6s are an inherently reliable valve design, so the fact the Groove Tubes (who are owned by Fender) "premium" 6L6 is so poor is disappointing.

     Howard really knows his stuff.

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  • @shaunm Dave Gascoigne at Rosewell Amps is good too. He's in South Elmsall. http://rosewell-amps.co.uk.

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  • jpfamps said:
    shaunm said:
    Thank you gents,

    I am booking it in with a tech. Can I ask you what would possibly cause a transformer to heat up to the point of burning up? 

    I am wondering if the person who put in the master volume mod did a hack job?
    MV mod should not have caused any over heating problems.

    Even the Custom Shop amps I've seen are wired for EU 230V AC rather than UK 240 AC, and this will cause the transformer to run hotter.

    Fender also used to shop their 6L6 loaded Custom Shop amps with their "premium" GT 6L6-GE. In my experience these are the most unreliable 6L6s on the market.

    I've had several sets of these expire straight out of the box.

    Hum is often caused by imbalance in the power valves.
    Without wishing to derail what is a good thread, what make of valves would @jpfamps recommend for a Fender amp? I've a Hot Rod Deluxe which I run clean, using pedals for distortion. I was thinking of replacing the stock Groove Tubes with Mesa Boogie valves.
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  • ICBMICBM Frets: 71963
    CarpeDiem said:

    Without wishing to derail what is a good thread, what make of valves would @jpfamps recommend for a Fender amp? I've a Hot Rod Deluxe which I run clean, using pedals for distortion. I was thinking of replacing the stock Groove Tubes with Mesa Boogie valves.
    There are no such thing as 'Mesa Boogie valves' - they're standard production valves from various factories, with Mesa labels on and higher prices. To be fair, they're well-tested and 'graded' for biasing purposes, but you can buy the same thing for less from any good vendor. I think Mesa are using JJs at the moment, but in the past they have used whatever Chinese or Russian valves are available cheaply and consistently.

    Karltone is good for any of the standard brands, including JJs.


    The 230V issue is an EU standards thing by the way - one of the few things that’s genuinely wrong with an EU directive :). Because the continental and UK/Ireland voltages were never really harmonised, just the tolerances widened to include both 220V and 240V, a '230V' amp in the UK runs too hot. For most equipment it makes no difference, but valve amps are unusual in that the voltages are stepped *up* not down inside, so the change is larger, and the excess power dissipation is related to the *square* of the voltage, so it can make quite a difference to valve life. There's also an issue in some amps with the low-voltage dropper resistors, which are under more stress at higher voltage.

    Luckily almost all Fender amps are easy to swap from 230V to 240V just by moving two wires on push-connectors.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • GassageGassage Frets: 30826
    Interesting thing re UK voltages. I have a view that Fenders were designed to run on 117v so that's what they should get. The best thing I have ever bought is my constant supply 117v transformer.

    *An Official Foo-Approved guitarist since Sept 2023.

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  • ICBMICBM Frets: 71963
    Gassage said:
    Interesting thing re UK voltages. I have a view that Fenders were designed to run on 117v so that's what they should get. The best thing I have ever bought is my constant supply 117v transformer.
    US models, yes. Their export models were designed to run on whatever voltage the selector is set to. If anything it's arguable that you should use 240V - or 260V on the 70s models that have it* - since that's using the full winding of the PT.

    *I have no idea why since no country has ever used such a voltage as far as I know, although it does have the advantage that you can deliberately set the late-70s high-HT-voltage models to it to reduce the stress on the valves. And where I work in central Glasgow has a measured voltage that is sometimes over 250V...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ICBM said:
    CarpeDiem said:

    Without wishing to derail what is a good thread, what make of valves would @jpfamps recommend for a Fender amp? I've a Hot Rod Deluxe which I run clean, using pedals for distortion. I was thinking of replacing the stock Groove Tubes with Mesa Boogie valves.
    There are no such thing as 'Mesa Boogie valves' - they're standard production valves from various factories, with Mesa labels on and higher prices. To be fair, they're well-tested and 'graded' for biasing purposes, but you can buy the same thing for less from any good vendor. I think Mesa are using JJs at the moment, but in the past they have used whatever Chinese or Russian valves are available cheaply and consistently.

    Karltone is good for any of the standard brands, including JJs.


    The 230V issue is an EU standards thing by the way - one of the few things that’s genuinely wrong with an EU directive :). Because the continental and UK/Ireland voltages were never really harmonised, just the tolerances widened to include both 220V and 240V, a '230V' amp in the UK runs too hot. For most equipment it makes no difference, but valve amps are unusual in that the voltages are stepped *up* not down inside, so the change is larger, and the excess power dissipation is related to the *square* of the voltage, so it can make quite a difference to valve life. There's also an issue in some amps with the low-voltage dropper resistors, which are under more stress at higher voltage.

    Luckily almost all Fender amps are easy to swap from 230V to 240V just by moving two wires on push-connectors.
    Many thanks for the information @ICBM
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  • RiftAmpsRiftAmps Frets: 3113
    tFB Trader
    And where I work in central Glasgow has a measured voltage that is sometimes over 250V...
    @ICBM I had 255V in the shop yesterday, not uncommon round here either
    *I no longer offer replacement speaker baffles*
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk

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  • jpfampsjpfamps Frets: 2724
    Gassage said:
    Interesting thing re UK voltages. I have a view that Fenders were designed to run on 117v so that's what they should get. The best thing I have ever bought is my constant supply 117v transformer.


    The transformers were also designed to run at 60 Hz mains; we have 50 Hz in the UK.

    In many respects this is more relevant than the "exact" voltage, as the lower frequency of UK mains is more likely to run the mains transform into saturation, and hence run too hot.
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  • jpfampsjpfamps Frets: 2724
    RiftAmps said:
    And where I work in central Glasgow has a measured voltage that is sometimes over 250V...
    @ICBM I had 255V in the shop yesterday, not uncommon round here either
    That's actually illegal (I assume you are measuring it with a true RMS  meter) although I expect reporting this to the relevant authorities will be a futile exercise.
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  • randellarandella Frets: 4088
    jpfamps said:
     Groove Tubes (who are owned by Fender)

    I've learned something new today then.  Aspen Pittman, was that his name?

    Hope you get the amp sorted.  The Bassman and the Deluxe Reverb are two amps I've never had a crack at and would like to.
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  • JezWyndJezWynd Frets: 6021
    RiftAmps said:
    And where I work in central Glasgow has a measured voltage that is sometimes over 250V...
    @ICBM I had 255V in the shop yesterday, not uncommon round here either
    Buy 240 volts, get 15 volts for free! Or are they?
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  • OssyrocksOssyrocks Frets: 1673
    jpfamps said:
    Gassage said:
    Interesting thing re UK voltages. I have a view that Fenders were designed to run on 117v so that's what they should get. The best thing I have ever bought is my constant supply 117v transformer.


    The transformers were also designed to run at 60 Hz mains; we have 50 Hz in the UK.

    In many respects this is more relevant than the "exact" voltage, as the lower frequency of UK mains is more likely to run the mains transform into saturation, and hence run too hot.
    This is true. I run my vintage BF Deluxe Reverb on a step down tranformer. The mains tranny gets too hot to touch. But I have been running it like this for over 20 years and it’s ok so far. It did worry me for the first ten years........

    Rob
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