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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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25th Apr 2018, 10:20 pm | #21 |
Pentode
Join Date: Nov 2016
Location: Wolverhampton, West Midlands, UK.
Posts: 117
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Re: Regentone hum
I did also wonder if the UL84 should be giving a faint blue glow?
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25th Apr 2018, 10:29 pm | #22 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,875
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Re: Regentone hum
Some folk pay money for that sticking blue LED's under the valves
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25th Apr 2018, 10:41 pm | #23 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
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Re: Regentone hum
It might be down to the fact its screen grid voltage is too high on account of the incorrect resistor value.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
1st Jun 2018, 2:25 am | #24 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Re: Regentone hum
Hi!
EL84/UL84 valves commonly exhibit dark blue internal fluorescence on the inside of their envelopes when operating normally, it is simply due to clouds of electrons leaving aperatures in the anode structures and in no way signifies any defect in the valve. It normally moves about the inside of the glass in a completely haphazard fashion. The glow from unwanted gas in a valve is much brighter and more purplish in colour and extends throughout the electrode – structure, such a valve is useless. Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
1st Jun 2018, 9:12 am | #25 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,336
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Re: Regentone hum
It's over a month since we've heard from the OP and we don't yet know if, by replacing the smoothing resistor, it has solved his hum problem? I know from many years of living with and working on UL84/UY85 based players, it is possible, especially with careful cable routing, to achieve a credibly low level of hum on such crude amplifiers. Often you will see players on auction sites listed as still having their "characteristic hum" - as if it was some kind of retro virtue.
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