Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dennyg on October 15, 2018, 09:38:37 am
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Hey guys - I built my first 50W amp back in Jan. All previous builds have been 20W or less. Having worshipped at the church of Merlin for my formative years, I adopted the no standby switch theology. However with the 50W build, I see the pre-amp plates getting hit with 420V for about 5 seconds before the heaters and caps warm up, after which they quickly settle in to their run-state well under their 300V max per datasheet.
Is this negatively impacting tube life or is it ok as is? I'm fine adding an S/B switch but would enjoy inputs from those of you who are service techs and see trends with no-standby amps failing at a greater rate than those those which include them.
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the pre-amp plates getting hit with 420V
I look it as Plate dissipation spec's, at 420, there is ~~~0 current, so 420 * 0 = :icon_biggrin:
as electron finally start moving, plate comes down, Pdis, isn't abused
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> pre-amp plates getting hit with 420V for about 5 seconds
Not a problem.
Euro datasheets often have a 600V limit for NO current (pre-warmup).
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You guys made my day - thanks for taking time to reply with a couple of validations of my 'no-standby' personal preference
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those of you who are service techs
the K.I.S.S. rules, one less mechanical thing to break, 2 less wires to trace :icon_biggrin:
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Note that if there's a DCCF stage then mitigation will be necessary http://www.valvewizard.co.uk/dccf.html