Eq 80 - UK Vintage Radio Repair and Restoration Discussion Forum

Alan Stepney · 1st May 2010, 2:20 pm

The EQ 80 was one of the few nonodes.
According to the Mullard data book, it was intended for use as an FM detector.

(It also says that it could be used as an AF amplifier, and they show a circuit using one on which all grids apart from g1 are strapped together, making it a tetrode.)

Has anyone ever encountered one and if so, in what?

Also, why would anyone wish to use one as a tetrode when there are plenty of alternatives?

Mr Moose · 1st May 2010, 2:29 pm

Hello,
Quite a lot of examples here:- http://www.radiomuseum.org/tubes/tube_eq80.html
Click on the year in the Usage In Models section.
Yours, Richard

Alan Stepney · 1st May 2010, 4:47 pm

As far as I can see, no British examples, and, not surprisingly, quite a few Philips.

FERNSEH · 1st May 2010, 11:08 pm

I believe that the EQ80 valve was developed by Philips and was first used in the Philips TX500 TV Receiver. The first 625 line set to be marketed in Holland. That was in 1950. The EQ80 was developed for use as the FM detector.

In the UK we used the much less complex EH90 in some dual standard receivers.

DFWB.

Synchrodyne · 2nd May 2010, 10:45 am

As best I can work out, the EQ80 was essentially a quadrature quasi-synchronous demodulator. Both the signal and quadrature feeds came from the final IF stage. On the other hand the EH90 looks to be more akin to a quadrature fully-synchronous demodulator, in that the quadrature feed was self-generated by locked oscillation.

Perhaps the EQ80 was aimed more at television applications. However, if it was also proposed for use in FM-AM receivers, then the AM side would have needed additional AF gain to match the relatively high EQ80 output level, and that might most conveniently have been obtained by using the EQ80 as an AF amplifier, with grid-strapping as needed for that function.

The American counterpart to the EQ80 seems to have been the gated beam valve; see: http://www.r-type.org/pdfs/6bn6a.pdf; and: http://www.clarisonus.com/Archives/T...BN6_part_2.pdf.

It’s interesting that quadrature FM demodulation, very much associated with the arrival of consumer electronics ICs, and perhaps particularly the CA3089 and its derivatives, actually goes back to the late 1940s.

Cheers,

1st May 2010, 2:20 pm	#1
Alan Stepney Rest in Peace Join Date: Feb 2008 Location: Dorset, UK. Posts: 947	Eq 80 The EQ 80 was one of the few nonodes. According to the Mullard data book, it was intended for use as an FM detector. (It also says that it could be used as an AF amplifier, and they show a circuit using one on which all grids apart from g1 are strapped together, making it a tetrode.) Has anyone ever encountered one and if so, in what? Also, why would anyone wish to use one as a tetrode when there are plenty of alternatives?

1st May 2010, 2:29 pm	#2
Mr Moose Octode Join Date: Jul 2008 Location: Gloucestershire, UK. Posts: 1,043	Re: Eq 80 Hello, Quite a lot of examples here:- http://www.radiomuseum.org/tubes/tube_eq80.html Click on the year in the Usage In Models section. Yours, Richard

1st May 2010, 4:47 pm	#3
Alan Stepney Rest in Peace Join Date: Feb 2008 Location: Dorset, UK. Posts: 947	Re: Eq 80 As far as I can see, no British examples, and, not surprisingly, quite a few Philips.

1st May 2010, 11:08 pm	#4
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Eq 80 I believe that the EQ80 valve was developed by Philips and was first used in the Philips TX500 TV Receiver. The first 625 line set to be marketed in Holland. That was in 1950. The EQ80 was developed for use as the FM detector. In the UK we used the much less complex EH90 in some dual standard receivers. DFWB.

2nd May 2010, 10:45 am	#5
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Eq 80 As best I can work out, the EQ80 was essentially a quadrature quasi-synchronous demodulator. Both the signal and quadrature feeds came from the final IF stage. On the other hand the EH90 looks to be more akin to a quadrature fully-synchronous demodulator, in that the quadrature feed was self-generated by locked oscillation. Perhaps the EQ80 was aimed more at television applications. However, if it was also proposed for use in FM-AM receivers, then the AM side would have needed additional AF gain to match the relatively high EQ80 output level, and that might most conveniently have been obtained by using the EQ80 as an AF amplifier, with grid-strapping as needed for that function. The American counterpart to the EQ80 seems to have been the gated beam valve; see: http://www.r-type.org/pdfs/6bn6a.pdf; and: http://www.clarisonus.com/Archives/T...BN6_part_2.pdf. It’s interesting that quadrature FM demodulation, very much associated with the arrival of consumer electronics ICs, and perhaps particularly the CA3089 and its derivatives, actually goes back to the late 1940s. Cheers,