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

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 14th Feb 2018, 10:20 pm   #1
Radio1950
Hexode
 
Join Date: Apr 2017
Location: Buderim, Queensland, Australia.
Posts: 428
Default Why did manufacturers use 5 volt heater rectifiers?

With reference to radio receivers from the 1930s through 1950s, why did manufacturers use 6.3 volt heater valves generally eg 6U7 etc, but used 5 volt heater rectifiers eg 5Y3 and the older 80?
Why did they not use 6.3 heater rectifiers?
What is the relevant history?
Radio1950 is offline  
Old 14th Feb 2018, 11:09 pm   #2
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Valves with 5-volt heaters predated valves with 6.3-volt heaters. The latter were introduced to suit auto radios in cars with 6-volt electrical systems, but were then also used for AC mains-operated receivers.

The rectifier valves of the time were directly heated, with one heater leg serving as the cathode, and therefore at high potential with respect to ground. Thus, whatver was their heater voltage, the rectifier valve heaters were supplied from a separate secondary winding on the power transformer, which could float at whatver DC voltage was on the rectifier "cathode".

The other heaters were supplied from another secondary winding, one side of which, or in some cases the centre-tap of which was grounded, keeping the whole heater system at close top ground potential.

Thus having the rectifier at a different voltage to the other valves was not an issue of consequence, given that they were supplied from different transformer windings. There was no need, therefore, to issue a new range of rectifier valves with 6.3-volt heaters.

Post-WWII the indirectly heated rectifier was developed, initially for auto radios, with sufficient heater-to-cathode insulation that the heater could be supplied from a low-potential source, such as the car battery and later the same transformer heater winding as used by the other valves Then of course it made sense to adopt 6.3-volt heaters. The indirectly heated rectifer then became the norm for domestic radio receivers, but the directly heated, 5-volt type was generally retained for the higher power applications.


Cheers,
Synchrodyne is offline  
Old 14th Feb 2018, 11:50 pm   #3
AC/HL
Dekatron
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Directly heated rectifier cathodes are made as a tape, which presumably suits low voltage high current. When indirectly heated cathodes came along there was no restriction on the heater voltage.
AC/HL is offline  
Old 15th Feb 2018, 12:13 am   #4
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
Default Re: Why did manufacturers use 5 volt heater rectifiers?

The tape-shaped directly heated cathode was to increase the surface area and hence the current that could be handled. A coiled filament could have been used but would haveself-masked a lot of its own area and would not have been as suitable for coating or surface treatment. The tape not only gave larger area, it had it facing in useful directions.

For a similar reason large transmitting valves tend to be directly heated and the heaters run huge currents at low voltages in search of the greatest emitted current per watt of heating with long-lived cathode materials.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 15th Feb 2018, 12:14 am   #5
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Indirectly heated rectifiers were around quite early on, the Mazda UU series and Mullard IW series are just some early indirect examples that were widely used in mid 30's UK radio's. These were all 4V heaters though.

The 5V standard seems to have come from the USA in the form of the 80 mentioned above. 2.5V and 5V filaments were used in late 1920's 'tubes'. No idea why they stuck with it although the argument that higher voltages would require thinner filaments with less surface area sounds reasonable.

Last edited by PJL; 15th Feb 2018 at 12:27 am.
PJL is offline  
Old 15th Feb 2018, 12:18 am   #6
Mr Moose
Octode
 
Join Date: Jul 2008
Location: Gloucestershire, UK.
Posts: 1,043
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Hello,
In the 1920s RCA and other American valve makers made mains valves with filaments in multiples of 2.5V. Low power valves were 2.5V higher power including many rectifiers were 5V, high power valves 7.5V and so on.
The first American full wave rectifier was the RCA UX280 (later abreviated to 80) in 1925 with a 5V 2A filament.
In the early 1930s many mains valves changed to 6.3V so they could be run off a 6V accumulator. The HT could come from a synchronous vibrator or motor generator (or later a cold cathode rectifier) saving the 10W for the rectifier heater so the rectifier could stay at 5V.
Yours, Richard
Mr Moose is offline  
Old 15th Feb 2018, 7:14 pm   #7
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: Why did manufacturers use 5 volt heater rectifiers?

4V directly-heated rectifiers also seemed to persist well into the post-WWII period in European radios whose other valves were 6.3V: I can remember quite a few instances of the AZ31:

http://www.r-type.org/exhib/aaq0099.htm

being used alongside the 6.3V ECH35/EF39/EBC33/6V6 lineup in generic 5-valve LW/MW/SW radios of the era.

Of course as for 5V directly-heated rectifiers this necessitated a power-transformer with a separate highly-insulated winding for the rectifier. Which seems to me to be utterly crazy when there were the likes of the 6X5

http://www.r-type.org/exhib/abh0072.htm

and 6X5GT:

http://www.r-type.org/exhib/aai0241.htm

which had heater-cathode insulationrated to 500V - available since 1936!

Last edited by G6Tanuki; 15th Feb 2018 at 7:35 pm.
G6Tanuki is offline  
Old 15th Feb 2018, 7:56 pm   #8
turretslug
Dekatron
 
turretslug's Avatar
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
Default Re: Why did manufacturers use 5 volt heater rectifiers?

The 6X5 series seems to have acquired a reputation as a transformer-killer in the US, though- perhaps there was a problem with early samples and the reputation just stuck, all sorts of things can get besmirched by anecdote and designer/consumer caution long after the event.

I wonder also if the 6X5/AZ31 thing reflected whether a setmaker was more rooted in European or American ownership/culture? NIH can be a significant consideration, even over-riding technical merit. The AZ31 has, like the 6X5, low heater power requirements, certainly good enough emission for a typical domestic set. It is directly heated, though. Maybe Philips had put significant effort into AZ31 production and development and it was available to setmakers cheaply in mainland Europe following the disappointment of the Ct8 AZ1. There seemed to be more of a divide between Continental and US setmakers re. valve series whereas the UK was content to straddle the divide (or Trojan Horse, as a famous post-war French statesman put it!).

No keen on DH rectifiers myself, having seen fractured tape filaments waving around in the anode cavity, just itching to cause havoc.

I gather that the EZ80/81 types benefited from the highly insulating experience gathered with TV boost diodes and eased fears of common heater powering from a single secondary winding.
turretslug is offline  
Old 15th Feb 2018, 8:10 pm   #9
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: Why did manufacturers use 5 volt heater rectifiers?

The 4V-filament-rectifier thing was perpetuated by Mazda/Mullard/Philips into the daft 'rimlock' B8A era:

http://www.r-type.org/exhib/aaa0973.htm

from 1947

Did anyone sane actually use this?
G6Tanuki is offline  
Old 15th Feb 2018, 8:24 pm   #10
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: Why did manufacturers use 5 volt heater rectifiers?

I see there's a 2015 thread that asks about all the heater voltages without any real conclusion as to why 4 volts itself came into use, other than as a multiple of 2 volts cells perhaps?

Dave W
dave walsh is offline  
Old 15th Feb 2018, 8:25 pm   #11
turretslug
Dekatron
 
turretslug's Avatar
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Eek! Direct heating and tiny clearances- not one I'll be scouring the rallies for. Having said that 5V heating seemed to be a US thing, there was also a late-in-the-day GZ41. No doubt, someone into that wacky and baroque world of post-war French domestic radios would come up with several examples using both these rectifier types...
turretslug is offline  
Old 15th Feb 2018, 8:27 pm   #12
Trifocaltrev
Hexode
 
Trifocaltrev's Avatar
 
Join Date: Nov 2013
Location: Lancing, West Sussex, UK.
Posts: 284
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Yes, it was used by many European Philips sets and other Continental sets, as were the DK40 series of battery valves. Neither are found in British sets.
Trifocaltrev is offline  
Old 15th Feb 2018, 9:23 pm   #13
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Why did manufacturers use 5 volt heater rectifiers?

The AZ41 was part of the original 1946 Philips Rimlock range, along with the EZ40 and EZ41. From the literature of the time, Philips clearly preferred the EZ40 and extolled its advantages. The inference is that the AZ41 was offered – probably with behind-the-scenes reluctance – because some equipment makers were yet to be convinced of the virtues of indirectly heated rectifiers.

In the USA, the 5Y3-GT was still being used in the early 1950s – including by RCA – despite the availability of indirectly heated alternatives. That does suggest that there was some nervousness – rational or otherwise – about indirectly heated rectifiers powered from a common heater winding.


Cheers,
Synchrodyne is offline  
Old 16th Feb 2018, 2:14 am   #14
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: Why did manufacturers use 5 volt heater rectifiers?

I always supposed it was done to force you to use a separate heater winding for the rectifier, thereby shifting the problem of insulation withstanding voltages from the heater (at / near chassis potential) and cathode (at full HT potential) of the rectifier valve to the power transformer. Yet the state of the art in heater-cathode insulation was already in use in series heater chains, where it had to be able to withstand almost peak-to-peak mains voltage (the cathode will always be positive, peak mains less the forward voltage drop of the rectifier; during the trough of the mains, the live end of the heater will be at negative peak mains less the peak voltage across the heater dropper resistor) -- more than the typical HT in a transformer-fed set. Also, a transformer tends to filter out interference spikes that may be present on the mains that a transformerless, series-heater set would have to withstand.

The EZ40 and its 9-pin successors, EZ80 and EZ81, were designed with high-voltage H-K insulation so as to be able to share a heater winding with the other valves in a set, but there must have been value in the other voltages -- perhaps some manufacturers could not quite bring themselves to trust the internal insulation in a valve? Mullard, Mazda and Brimar would not have been too bothered what setmakers thought -- whether they were being avant-garde and reckless placing misguided faith in fancy new insulation that promised to enable the use of common heater windings, or stuffy and conservative by insisting to have a traditional, separate winding for the rectifier heater -- as long as they were buying the valves, and they could make both sorts just as easily as each other .....
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline  
Old 16th Feb 2018, 7:13 am   #15
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Quote:
Originally Posted by G6Tanuki View Post
The 4V-filament-rectifier thing was perpetuated by Mazda/Mullard/Philips into the daft 'rimlock' B8A era:

http://www.r-type.org/exhib/aaa0973.htm

from 1947

Did anyone sane actually use this?
And then they went completely in the opposite direction with the equally crazy U404. Another B8A based rectifier. Never seen one though.
Sam.
Boater Sam is offline  
Old 16th Feb 2018, 12:05 pm   #16
G8HQP Dave
Rest in Peace
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
Default Re: Why did manufacturers use 5 volt heater rectifiers?

An indirectly-heated rectifier means the set takes slightly longer to work after switching on. This could be a disadvantage in a market aimed at ordinary folk. Hence the option of a directly heated rectifier was maintained as long as setmakers required it.
G8HQP Dave is offline  
Old 17th Feb 2018, 4:28 am   #17
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Why did manufacturers use 5 volt heater rectifiers?

From which perspective the AZ41 looks to have been a reasonable offering by Philips, supplementary to the EZ40, the latter being the principal rectifier valve in its initial post-WWII miniature AC receiving range. The availability of the AZ41 would have enabled those setmakers who wished to retain directly-heated rectifiers to still move to an all-miniature valve line-up. That the AZ41 was 70 mA capacity as compared with 90 mA for the EZ40 suggests that it was with the simpler receivers of the era that warm-up time might have been a potential customer issue.

Quote:
Originally Posted by Boater Sam View Post
And then they went completely in the opposite direction with the equally crazy U404. Another B8A based rectifier.
The U404 was the standard half-wave rectifier in Mazda’s initial post-WWII miniature AC-DC receiving valve range. It was proximate to the Philips EY41. Whilst I should not wish to argue the negative on the proposition that the perpetuation of AC-DC receivers for general use, that is beyond the specialty niche of users who had DC power supplies, was in and of itself “crazy”, nevertheless within the confines of that concept the Mazda U404 appears to have been normal and reasonable.


Cheers,
Synchrodyne is offline  
Old 17th Feb 2018, 7:56 am   #18
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Never one to argue the negative on a proposition myself either.

Seen an unusual to these shores modern valve for sale today, PM84 indicator. 4.2 v 300mA heater, now what were these used in? Ah, of course, continental TVs mostly, not my bailiwick. National Valve Museum has no listing.
Anyone want to add a magic eye to a 4v heater radio?

I have in stock a 2103PT anyone know it? I thought it could be 210SPT or 210VPT but it looks clearly like a "3"

Last edited by Boater Sam; 17th Feb 2018 at 7:58 am. Reason: correction
Boater Sam is offline  
Old 17th Feb 2018, 1:17 pm   #19
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Why did manufacturers use 5 volt heater rectifiers?

It was used in the Ultra 1750/60 series TV/FM receiver. J.
Heatercathodeshort is offline  
Old 17th Feb 2018, 9:05 pm   #20
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Why did manufacturers use 5 volt heater rectifiers?

Quote:
Originally Posted by Boater Sam View Post
Seen an unusual to these shores modern valve for sale today, PM84 indicator. 4.2 v 300mA heater, now what were these used in? Ah, of course, continental TVs mostly, not my bailiwick. National Valve Museum has no listing.
Anyone want to add a magic eye to a 4v heater radio?

There was a magic eye in the 4-volt series, namely the Mazda ME41. It was used by Dynatron post-WWII in its T69 series of tuner/control unit combinations, I think from the T69B onwards.

The PM84 also had some radio receiver applications, such as in the B&O 606K, which was an AC-DC chassis with 300 mA series-string valves. But as you say, TV receivers were probably the main application. The use of magic eye tuning indicators in TV receivers was apparently one of those recurring themes that never became mainstream, but for example, Wireless World for 1961 November (p.560) noted that some then-current French TV receivers were fitted with magic eyes. If these were AC-DC (and I have a vague notion that not all French receivers were), then the PM84 was a likely candidate for the magic eye job.


Cheers,
Synchrodyne is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:30 am.


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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.