UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Reply
 
Thread Tools
Old 17th Apr 2019, 3:28 pm   #1
trickie_dickie
Hexode
 
trickie_dickie's Avatar
 
Join Date: Jan 2011
Location: Aberdare, South Wales, UK
Posts: 304
Default Voltage Regulator Valves eg OA2

Are these valves noisy? I was thinking of using them in an amp in series with the screens on the output pentodes. Also interstage coupling instead of capacitors. Any thoughts?
__________________
Richard
trickie_dickie is offline   Reply With Quote
Old 17th Apr 2019, 3:44 pm   #2
GrimJosef
Nonode
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 2,376
Default Re: Voltage Regulator Valves eg OA2

Yes. I'm afraid they are somewhat noisy. In some cases the 'special quality' versions have their noise properties specified (not necessarily reduced very much, just specified). Depending on the details you're interested in they can be quite a bit less noisy than Zener diodes of the same voltage rating. But the advantage of Zeners is that the noise can be filtered out using a large parallel capacitor. The discharge regulators, by contrast, have a negative resistance region in their characteristic and putting more than a few tens of nanofarads (perhaps a hundred nanofarads, if you're brave) directly across them can cause them to burst into catastrophic oscillation. I've never seen it but I'm told it's pretty exciting to watch, from a safe distance of course.

Cheers,

GJ
__________________
http://www.ampregen.com
GrimJosef is online now   Reply With Quote
Old 17th Apr 2019, 4:48 pm   #3
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 6,985
Default Re: Voltage Regulator Valves eg OA2

Yes, they are noisy - indeed in some equipment discharge-tubes have been used as a source of wideband noise, either to drive 'jammer' transmitters or to feed random-number generators. (In later years photomultiplier tubes were found to be ideal for this application)

As mentioned, paralleling them with too much 'C' can produce a nice relaxation-oscillator. I use a series-connected pair of such valves to provide the regulated screen-supply for a parallel-pair of 6146 in a linear-amp, and there's only 5nF paralleling them. So far no oscillations!
G6Tanuki is online now   Reply With Quote
Old 17th Apr 2019, 5:32 pm   #4
Craig Sawyers
Octode
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 1,682
Default Re: Voltage Regulator Valves eg OA2

Ernie 1 used cold cathode valves (like an OA2) as the random noise source. The particular unit used was a QS92/10, which is a 92V regulator valve.

Ernie 1 schematics and description of the design are here http://www.tnmoc.org/sites/default/f...technology.pdf

So yes - regulator valves are noisy!
Craig Sawyers is online now   Reply With Quote
Old 17th Apr 2019, 6:39 pm   #5
Megatron
Triode
 
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 47
Default Re: Voltage Regulator Valves eg OA2

I have used them on 807s in series to drop voltage due to the limited voltage rating of the screen, I used 85A2 IIRC.
couldn't actually hear any significant noise in the speakers.
If you drive the amp well into clipping though it could cause some problems.
ie when the anode voltage drops below reg voltage.

For measuring conducted emissions in the 9kHz-30MHz range we actually use a pair of neons across the line as a noise source.
at 150kHz the emission peak value is pretty much on the conducted emission limit~66dbuV however these are on AC50Hz therefore theres a lot of switching noise when they strike. never tried one on DC, must have a go now its been brought up.

Last edited by Megatron; 17th Apr 2019 at 6:47 pm.
Megatron is offline   Reply With Quote
Old 18th Apr 2019, 12:20 pm   #6
G8HQP Dave
Dekatron
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,691
Default Re: Voltage Regulator Valves eg OA2

Using them as a dropper means they act as a voltage deregulator.

Interstage coupling might be interesting. Apart from the noise and current flow (typically 5mA minimum) they are sluggish to respond to voltage changes, which is why you can get away with a low value parallel cap but not a bigger cap. You might get a built-in tone control.
G8HQP Dave is offline   Reply With Quote
Old 19th Apr 2019, 11:43 am   #7
Biggles
Nonode
 
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,074
Default Re: Voltage Regulator Valves eg OA2

You can make an oscillator using a neon lamp and a resistor/capacitor combination. The oscillation is due to the striking voltage being higher than the normal discharge maintenance voltage. So you need to be careful if you are adding parallel capacitors to a normal dropper resistor combination in case you unwittingly create an oscillator.
Alan.
Biggles is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 3:47 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.