Getting rid of the rattle on a Vox VT40+

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  • VinylfanVinylfan Frets: 33
    Ok - it is a VT40+ so how difficult is it to change the valve?  But before we get to that, is it likely to be the valve based on the tests I've done so far?  Tests have mainly been around getting the hiss/rattle reduced by turning the power level down and upping the volume (and reducing it further by turning the treble down).  

    Also, how much is a valve likely to cost?

    Thanks
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  • ICBMICBM Frets: 71960
    The hiss does definitely come from the part of the circuit that contains the valve, although whether the valve itself is responsible, I don't know.

    I can't find any inside shots of the VT40+, but if it's more like the VT30 it will be easy...



    A valve is about £10, so if you fancy having a go it's worth a try.

    http://www.karltone.co.uk/ecc83-12ax7-53-c.asp

    Sovteks (especially the WB) tend to be darker-sounding than some of the others so I would probably start there.

    "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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  • VinylfanVinylfan Frets: 33
    edited May 2018
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?

    Edit - just watched the video properly!  So ignore the question.
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  • ICBMICBM Frets: 71960
    Vinylfan said:
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?
    It’s all in the video...

    The only things I would add are that the back panel is easier to get off and put back if you loosen the side chassis bolts slightly first, and tighten them last.

    And that I don’t know what the sock thing is all about :).

    "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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  • VinylfanVinylfan Frets: 33
    ICBM said:
    Vinylfan said:
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?
    It’s all in the video...

    The only things I would add are that the back panel is easier to get off and put back if you loosen the side chassis bolts slightly first, and tighten them last.

    And that I don’t know what the sock thing is all about :).
    The sock was my favourite part - I've just been to M&S and bought some long beige socks in readiness!
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  • VinylfanVinylfan Frets: 33
    edited May 2018
    Quick update.
    I've opened it up - slightly different to the video, but the board with the valve comes away and out quite easily.  I sprayed a little contact cleaner on the speaker connectors for good measure and made sure all the other connectors were seated in firmly.

    Anyway, the valve inside is labelled 'Ruby 12AX7AC5' in red on the tube.  I don't recall seeing any leds near the valve so I'm sure any glow is from the valve.

    Not sure if this valve is original or if I should just try another valve entirely - and if I'd notice the difference.  Any pointers gratefully received.  They had an Electro Harmonix one on the site linked to earlier and quite a choice of others.
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  • ICBMICBM Frets: 71960
    The only way you'll know if it's the valve is to try another one. Rubys are Chinese-made and all Chinese 12AX7s are brighter-sounding in general. Avoid EH and Tung-Sol if brightness/hiss is a problem - they're also bright, which is odd because they come from the same factory as Sovteks, which are much darker. Sovtek WB would be my first choice, followed by Sovtek WA, and then JJ which tend to have a 'muddy/middy' character.

    At least, this is how they perform in standard high-voltage valve amp circuits. Whether that's true at the much lower voltages here - even if the filament is running at the normal voltage - I don't know.

    "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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  • fandangofandango Frets: 2204
    Is it too late to call The Fonz ....

    https://www.youtube.com/watch?v=zQsKa7dYu2w
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