5763 vs EL84? - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 28th Jul 2022, 12:25 pm

The 5763 (QV03/12) and the EL84... Do they share heritage??

What makes me suspect 'something was going on' in the design office is that both have an unusual heater current.. The 5763 js 0.75A at 6V and the EL84 is 0.76A @6.3V.

Same heater/cathode assembly??

I have used an EL84 successfully in a 15-watt anode modulated 3.5Mhz transmitter where the designer originally specified a 5763 and it worked fine.

Aub · 28th Jul 2022, 3:17 pm

Yes, the EL84 works fine at 3.5mHz and probably higher, but i think the 5763 will go a lot higher as its classed as a transmitting valve in data books. Not sure if the audio folks have been after 5763 yet

Cheers

Aub

Cruisin Marine · 28th Jul 2022, 5:02 pm

I always thought the 6BW6 looked identical to the 5763, having very slightly different pin outs though

turretslug · 28th Jul 2022, 5:33 pm

I don't know how often it was used as such, but Eddystone certainly used the 5763 as an audio-output valve in the 910 marine receiver, effectively a heavily-developed tunable-IF follow-on to the 750 and a stepping-stone to the 830. Another receiver that conspicuously didn't use the EL84 was the Pye CAT, using the broadly comparable 6CH6/EL821 instead- originally pitched as a wideband video amplifier. Maybe these professional-market valves were felt to be more dependable than the consumer-pitched EL84?

G6Tanuki · 28th Jul 2022, 6:25 pm

The 5763 is a beam-tetrode [according to Brimar - http://www.r-type.org/exhib/aam0048.htm ] as is Mullard's QV03/12 - http://www.r-type.org/exhib/aaa0030.htm - I guess there is common heritage here - but the EL84 - http://www.r-type.org/exhib/aaa0028.htm - is always shown as a pentode.

Brimar did indeed spec the 6BW6 [which is really the electrode-assembly of that old workhorse the 6V6 fitted into a small bottle ] - as "suitable for R.F. application up to frequencies of the order of 150 Mc/s"

And equally, a pair of them in Class-AB2 could be worked to produce 30 Watts of audio. Did trhe Mullard///Philips guys publish similar stats for 'overworking' the EL84? [I don't recall ever seeing the EL84 being used in ham-radio modulators to deliver more than about 17 Watts ... ] If so I'd have expected guitar-amp makers to have produced "30-Watt" amps using the EL84. Remember that the EL84 took rather more heater-current than the 6BW6,... so saving on heater-transformer-power would have been a big thing in favour of the 6BW6 over the EL84.

For reference, the attached photo shows - on the left, a Mullard 5763, next an Edicron EL84 [there's a thread about these going on currently] and on the right a Brimar 6BW6.

The 'cuckoo-in-the-nest' in this photo, between the EL84 and the 6BW6 is a "Pinnacle"-rebranded RCA 10GK6 - which is a sort-of EL84 with a different pin-out and a 10V 0.45A heater... https://www.radiomuseum.org/tubes/tube_10gk6.html

They're available cheaply and can be thrashed just as hard as the EL84 both for audio and RF duty.... But don't tell the audiophools...

Interestingly, the 10GK6's 6.3V-heater buddy the 6GK6 draws 0.76A at 6.3v... now where have we seen that odd 0.76A current-draw before?... https://www.radiomuseum.org/tubes/tube_6gk6.html

28th Jul 2022, 12:25 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	5763 vs EL84? The 5763 (QV03/12) and the EL84... Do they share heritage?? What makes me suspect 'something was going on' in the design office is that both have an unusual heater current.. The 5763 js 0.75A at 6V and the EL84 is 0.76A @6.3V. Same heater/cathode assembly?? I have used an EL84 successfully in a 15-watt anode modulated 3.5Mhz transmitter where the designer originally specified a 5763 and it worked fine. __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.

28th Jul 2022, 3:17 pm	#2
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,039	Re: 5763 vs EL84? Yes, the EL84 works fine at 3.5mHz and probably higher, but i think the 5763 will go a lot higher as its classed as a transmitting valve in data books. Not sure if the audio folks have been after 5763 yet Cheers Aub __________________ Life's a long song, but the tune ends too soon for us all.

28th Jul 2022, 5:02 pm	#3
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 992	Re: 5763 vs EL84? I always thought the 6BW6 looked identical to the 5763, having very slightly different pin outs though

28th Jul 2022, 5:33 pm	#4
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,395	Re: 5763 vs EL84? I don't know how often it was used as such, but Eddystone certainly used the 5763 as an audio-output valve in the 910 marine receiver, effectively a heavily-developed tunable-IF follow-on to the 750 and a stepping-stone to the 830. Another receiver that conspicuously didn't use the EL84 was the Pye CAT, using the broadly comparable 6CH6/EL821 instead- originally pitched as a wideband video amplifier. Maybe these professional-market valves were felt to be more dependable than the consumer-pitched EL84?

28th Jul 2022, 6:25 pm	#5
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: 5763 vs EL84? The 5763 is a beam-tetrode [according to Brimar - http://www.r-type.org/exhib/aam0048.htm ] as is Mullard's QV03/12 - http://www.r-type.org/exhib/aaa0030.htm - I guess there is common heritage here - but the EL84 - http://www.r-type.org/exhib/aaa0028.htm - is always shown as a pentode. Brimar did indeed spec the 6BW6 [which is really the electrode-assembly of that old workhorse the 6V6 fitted into a small bottle ] - as "suitable for R.F. application up to frequencies of the order of 150 Mc/s" And equally, a pair of them in Class-AB2 could be worked to produce 30 Watts of audio. Did trhe Mullard///Philips guys publish similar stats for 'overworking' the EL84? [I don't recall ever seeing the EL84 being used in ham-radio modulators to deliver more than about 17 Watts ... ] If so I'd have expected guitar-amp makers to have produced "30-Watt" amps using the EL84. Remember that the EL84 took rather more heater-current than the 6BW6,... so saving on heater-transformer-power would have been a big thing in favour of the 6BW6 over the EL84. For reference, the attached photo shows - on the left, a Mullard 5763, next an Edicron EL84 [there's a thread about these going on currently] and on the right a Brimar 6BW6. The 'cuckoo-in-the-nest' in this photo, between the EL84 and the 6BW6 is a "Pinnacle"-rebranded RCA 10GK6 - which is a sort-of EL84 with a different pin-out and a 10V 0.45A heater... https://www.radiomuseum.org/tubes/tube_10gk6.html They're available cheaply and can be thrashed just as hard as the EL84 both for audio and RF duty.... But don't tell the audiophools... Interestingly, the 10GK6's 6.3V-heater buddy the 6GK6 draws 0.76A at 6.3v... now where have we seen that odd 0.76A current-draw before?... https://www.radiomuseum.org/tubes/tube_6gk6.html Attached Thumbnails __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk. Last edited by G6Tanuki; 28th Jul 2022 at 6:31 pm.