Marconi VC76DA - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Edward Huggins · 11th Oct 2017, 10:25 am

I read these TV Threads in awe. It's a long time since I've had my hands on a late 1940s chassis and made at a time of materials shortages, they are just so full of hardware....Noting the use on an (IF valve) EF91 as an audio output valve what kind of power did they give? Surely they would not be capable of much more than 500mW?

Heatercathodeshort · 11th Oct 2017, 4:48 pm

I know, it's amazing. You would not know by the quality and quantity of audio available from that incredible little valve, the EF91.

There were a number of manufacturers that used it as an audio output valve including I believe KB. EMI also employed the EF80 in a couple of models.

I would guess around 750mw was available with an HT line around 220v, more than enough for the average living room.

A quite amazing valve manufactured in it's best form by Mullard as the EF91 and Mazda in the form of the 6F12 who I believe actually designed it around 1946. Regards, John.

Halfabee · 11th Oct 2017, 4:54 pm

Hi Edward,

It was indeed a strange quirk (one of many) of E.M.I. AC/DC televisions to use an RF pentode as the audio output valve, an EF91 in the 1807 series and an EF80 in subsequent chassis.
I guess households were quieter in the early '50s, the TV not having to compete against a plethora of other noise generating electrical appliances!

Cheers
Eric.

Halfabee · 11th Oct 2017, 4:57 pm

Apologies... John beat me to it!

11th Oct 2017, 10:25 am	#21
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,325	Re: Marconi VC76DA I read these TV Threads in awe. It's a long time since I've had my hands on a late 1940s chassis and made at a time of materials shortages, they are just so full of hardware....Noting the use on an (IF valve) EF91 as an audio output valve what kind of power did they give? Surely they would not be capable of much more than 500mW? __________________ Edward.

11th Oct 2017, 4:48 pm	#22
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Marconi VC76DA I know, it's amazing. You would not know by the quality and quantity of audio available from that incredible little valve, the EF91. There were a number of manufacturers that used it as an audio output valve including I believe KB. EMI also employed the EF80 in a couple of models. I would guess around 750mw was available with an HT line around 220v, more than enough for the average living room. A quite amazing valve manufactured in it's best form by Mullard as the EF91 and Mazda in the form of the 6F12 who I believe actually designed it around 1946. Regards, John.

11th Oct 2017, 4:54 pm	#23
Halfabee Triode Join Date: Apr 2007 Location: Glasgow, UK. Posts: 49	Re: Marconi VC76DA Hi Edward, It was indeed a strange quirk (one of many) of E.M.I. AC/DC televisions to use an RF pentode as the audio output valve, an EF91 in the 1807 series and an EF80 in subsequent chassis. I guess households were quieter in the early '50s, the TV not having to compete against a plethora of other noise generating electrical appliances! Cheers Eric. __________________ Never overestimate the intelligence of the viewer

11th Oct 2017, 4:57 pm	#24
Halfabee Triode Join Date: Apr 2007 Location: Glasgow, UK. Posts: 49	Re: Marconi VC76DA Apologies... John beat me to it! __________________ Never overestimate the intelligence of the viewer