Regentone hum - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

12jslater · 25th Apr 2018, 10:20 pm

I did also wonder if the UL84 should be giving a faint blue glow?

Cobaltblue · 25th Apr 2018, 10:29 pm

Some folk pay money for that sticking blue LED's under the valves

Station X · 25th Apr 2018, 10:41 pm

Quote:

Originally Posted by 12jslater

I did also wonder if the UL84 should be giving a faint blue glow?

It might be down to the fact its screen grid voltage is too high on account of the incorrect resistor value.

Chris55000 · 1st Jun 2018, 2:25 am

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

Edward Huggins · 1st Jun 2018, 9:12 am

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.

25th Apr 2018, 10:20 pm	#21
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Re: Regentone hum I did also wonder if the UL84 should be giving a faint blue glow?

25th Apr 2018, 10:29 pm	#22
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,866	Re: Regentone hum Some folk pay money for that sticking blue LED's under the valves __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

1st Jun 2018, 2:25 am	#24
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,870	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 __________________ 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
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,328	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. __________________ Edward.