Do you know this valve? Mullard QV05-25 - UK Vintage Radio Repair and Restoration Discussion Forum

Cre8anet · 2nd Aug 2007, 11:09 pm

Hi - I suspect this is the right forum for this post (pls correct me if wrong)

Can anyone tell me what kit used this tube? and for what function?

I think this was a transmitter tube of moderate power, but keen to tap anyone's greater wisdom.

Especially if it's been successfully put to other uses.

Cheers,

Dave

Alf · 3rd Aug 2007, 12:17 am

It's an 807 in disguise, look up the 807

Skywave · 3rd Aug 2007, 7:49 pm

Hi!

Mullard QV05-25; do I know that valve?
Bet your life I do - and so do a lot of Radio Amateurs!

It's Mullard's version of the ubiquotous 807: as popularly featured in the WW2 transceiver the "19 set" - amongst others.

Although it is intended primarily as a "small transmitting valve", it pops up in all sorts of places: high-power AF amps., modulators for AM transmitters, pass-valve in linear regulated power supplies, early / vintage signal generators, RF amplifiers (class - A, B and C) to 60 MHz (reduced power O/P to 120 MHz).

It's a beam tetrode on a UX5 base.
Va max 600-v., Ia max. 100 mA, max. plate dissipation 25-watts (hence the "25" in QV05-25), 40w max. RF output.

One of the oldest "universal" power valves in the business. Been around for ages. Only possible snag is its high power gain: so you have to take the usual precautions at RF to avoid instability.

Al / Skywave / 03-08-07 //

Cre8anet · 3rd Aug 2007, 11:08 pm

Fantastic - thanks both! I'll digest this lot and do some more thinking/searching.

Is it fairly available do you think?

Dave

Skywave · 5th Aug 2007, 1:08 pm

Hi.

Is it (QV05-25) "fairly available"?

Not wishing to indulge in petty pedantry, it kinda depends on your criterion of "fairly available"

. . . e.g. in Amateur Radio circles (especially Old Timers), most likely . . . . from places like Maplins . . . no chance!

If you are after NOS, try the usual commercial outlets - like Billington Valves, etc. A quick Browse on the 'Net should reveal sources.

A general "ask" on this Forum could produce a favourable result.

Al / Skywave

MALC SCOTT · 5th Aug 2007, 7:32 pm

A couple of years ago i bought a couple of new old stock 807 valves from Russia via ebay. The total cost was less than a tenner and the valves were of very good quality.

2nd Aug 2007, 11:09 pm	#1
Cre8anet Pentode Join Date: Nov 2005 Location: Banbury, Oxfordshire, UK. Posts: 204	Do you know this valve? Mullard QV05-25 Hi - I suspect this is the right forum for this post (pls correct me if wrong) Can anyone tell me what kit used this tube? and for what function? I think this was a transmitter tube of moderate power, but keen to tap anyone's greater wisdom. Especially if it's been successfully put to other uses. Cheers, Dave

3rd Aug 2007, 12:17 am	#2
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Do you know this valve? Mullard QV05-25 It's an 807 in disguise, look up the 807

3rd Aug 2007, 7:49 pm	#3
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Do you know this valve? Mullard QV05-25 Hi! Mullard QV05-25; do I know that valve? Bet your life I do - and so do a lot of Radio Amateurs! It's Mullard's version of the ubiquotous 807: as popularly featured in the WW2 transceiver the "19 set" - amongst others. Although it is intended primarily as a "small transmitting valve", it pops up in all sorts of places: high-power AF amps., modulators for AM transmitters, pass-valve in linear regulated power supplies, early / vintage signal generators, RF amplifiers (class - A, B and C) to 60 MHz (reduced power O/P to 120 MHz). It's a beam tetrode on a UX5 base. Va max 600-v., Ia max. 100 mA, max. plate dissipation 25-watts (hence the "25" in QV05-25), 40w max. RF output. One of the oldest "universal" power valves in the business. Been around for ages. Only possible snag is its high power gain: so you have to take the usual precautions at RF to avoid instability. Al / Skywave / 03-08-07 //

3rd Aug 2007, 11:08 pm	#4
Cre8anet Pentode Join Date: Nov 2005 Location: Banbury, Oxfordshire, UK. Posts: 204	Re: Do you know this valve? Mullard QV05-25 Fantastic - thanks both! I'll digest this lot and do some more thinking/searching. Is it fairly available do you think? Dave

5th Aug 2007, 1:08 pm	#5
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Do you know this valve? Mullard QV05-25 Hi. Is it (QV05-25) "fairly available"? Not wishing to indulge in petty pedantry, it kinda depends on your criterion of "fairly available" . . . e.g. in Amateur Radio circles (especially Old Timers), most likely . . . . from places like Maplins . . . no chance! If you are after NOS, try the usual commercial outlets - like Billington Valves, etc. A quick Browse on the 'Net should reveal sources. A general "ask" on this Forum could produce a favourable result. Al / Skywave

5th Aug 2007, 7:32 pm	#6
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Re: Do you know this valve? Mullard QV05-25 A couple of years ago i bought a couple of new old stock 807 valves from Russia via ebay. The total cost was less than a tenner and the valves were of very good quality. __________________ Malc Scott