Substituting radio valves for TV valves. - UK Vintage Radio Repair and Restoration Discussion Forum

Ed_Dinning · 29th Jan 2006, 10:51 pm

Hi Gents, while doing a long overdue sort of my valve stock I found, as most of us will have, lots of P series TV valves. There were a lot of octal rectifiers that tested OK and seemed a pity to bin. An examination of the characteristics of the PY32/33 shows it would be a good sub for the 25Z4 series that were fitted to many AC/DC sets. I'm not sure if a base rewire is needed but voltage is close enough at 29V @0.3A . The PZ 30 with a 52 V heater at 0.3A could be useful is a section of the dropper is burnt out and you need an extra 25V from somewhere. I'll need to check further but some of the early Line and frame o/p valves may also be suitable for these AC/Dc sets.
Anyone else got any subs like this?

Ed

Aerodyne · 30th Jan 2006, 1:48 pm

No other subs come to mind, Ed, but like you I've used the PYs as subs for the 25s - but only as a temporary measure. so far.
-Tony

Nickthedentist · 30th Jan 2006, 7:13 pm

What a good idea, Ed

.

P-series valves can frequently be had for virtually nothing, and I've always suspected someone could put at least some of them to good use in audio equipment.

Nick.

Tim · 30th Jan 2006, 8:08 pm

I have an AC/DC version of the HMV1117. The output valve was missing,(KT33?) (all the others were 300mA heaters) and have found a PL33 works very well.

I have also heard a 20P3 can work in place of a CL33.

Ed_Dinning · 30th Jan 2006, 9:12 pm

Hi Gents, when we were really desparate for a triode pentode on a pre-war Cossor TV, an ECL 80 was pressed into service, fitted on the old B7 valve base and with a tiny auto transformer for the 4 to 6.3 V conversion. No other mods were required and it worked a treat. Start thinking about it gents!

Ed

quantum · 30th Jan 2006, 9:29 pm

If you are putting together an audio amp, many of the old tranny amps of the '60s and '70s used a mains transformer with a secondary giving about 17v, and one of these could be employed in addition to the HT tranny to power the heaters of valves such as PL82s and PLC82s with a slight overrun. I remember that Sir Douglas Hall published a circuit in Radio Constructor of a hybrid amp which used one of these transfomers with a PL82 (relying on its ability to amplify in a linear fashion with a very low HT).

I did experiment years ago with an amp where I had connected the two 6.3 volt windings on a mains tranny (the heater and the rectifier windings) in series to produce 12.6v, and used a PCL83 as an amp valve.

I also remember using a PL33 in a radio which previously had a valve of the 25A6/25L6 variety, and it worked OK although I should have really looked at the heater chain to ensure optimum working.

jay_oldstuff · 30th Jan 2006, 9:54 pm

the prototype of my one chip one valve radio(i promise i will wright this little set up one day) used a pcl83 as its output, basicaly the whole set used junk from the scrap plie it used two 12.5v transformers one 600ma one 300ma the 600ma one was conected to mains like normal with the valve filament conected to the transformers secondary the secondary of the 300ma transformer was then conected in paralell and the primary prodused about 220v ac after rectification and smoothing we had 200v for the HT. must admit though in the end i used an ecl80 and an normal transformer 6v + 200v from a scrap tape recorder due to space restraints

Jay

Alf · 30th Jan 2006, 10:53 pm

Quote:

I remember that Sir Douglas Hall published a circuit in Radio Constructor of a hybrid amp which used one of these transfomers with a PL82

Is this the one?

http://sites.ecosse.net/Vac.Repairs/...or/circuit.jpg

quantum · 5th Feb 2006, 3:28 pm

Yes, that's the one. I did think about making it once but never got around to it. It fascinated me that you would still get useful amplification from a PL82 even with such a low HT...

29th Jan 2006, 10:51 pm	#1
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Substituting radio valves for TV valves. Hi Gents, while doing a long overdue sort of my valve stock I found, as most of us will have, lots of P series TV valves. There were a lot of octal rectifiers that tested OK and seemed a pity to bin. An examination of the characteristics of the PY32/33 shows it would be a good sub for the 25Z4 series that were fitted to many AC/DC sets. I'm not sure if a base rewire is needed but voltage is close enough at 29V @0.3A . The PZ 30 with a 52 V heater at 0.3A could be useful is a section of the dropper is burnt out and you need an extra 25V from somewhere. I'll need to check further but some of the early Line and frame o/p valves may also be suitable for these AC/Dc sets. Anyone else got any subs like this? Ed

30th Jan 2006, 1:48 pm	#2
Aerodyne Octode Join Date: Jun 2004 Location: Hampton Vale, Peterborough, UK. Posts: 1,698	Re: Hard to find valve substitutes No other subs come to mind, Ed, but like you I've used the PYs as subs for the 25s - but only as a temporary measure. so far. -Tony

30th Jan 2006, 7:13 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Hard to find valve substitutes What a good idea, Ed. P-series valves can frequently be had for virtually nothing, and I've always suspected someone could put at least some of them to good use in audio equipment. Nick.

30th Jan 2006, 8:08 pm	#4
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: Hard to find valve substitutes I have an AC/DC version of the HMV1117. The output valve was missing,(KT33?) (all the others were 300mA heaters) and have found a PL33 works very well. I have also heard a 20P3 can work in place of a CL33. __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

30th Jan 2006, 9:12 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Hard to find valve substitutes Hi Gents, when we were really desparate for a triode pentode on a pre-war Cossor TV, an ECL 80 was pressed into service, fitted on the old B7 valve base and with a tiny auto transformer for the 4 to 6.3 V conversion. No other mods were required and it worked a treat. Start thinking about it gents! Ed

30th Jan 2006, 9:29 pm	#6
quantum Retired Dormant Member Join Date: Mar 2003 Location: Birmingham, West Midlands, UK. Posts: 785	Re: Hard to find valve substitutes If you are putting together an audio amp, many of the old tranny amps of the '60s and '70s used a mains transformer with a secondary giving about 17v, and one of these could be employed in addition to the HT tranny to power the heaters of valves such as PL82s and PLC82s with a slight overrun. I remember that Sir Douglas Hall published a circuit in Radio Constructor of a hybrid amp which used one of these transfomers with a PL82 (relying on its ability to amplify in a linear fashion with a very low HT). I did experiment years ago with an amp where I had connected the two 6.3 volt windings on a mains tranny (the heater and the rectifier windings) in series to produce 12.6v, and used a PCL83 as an amp valve. I also remember using a PL33 in a radio which previously had a valve of the 25A6/25L6 variety, and it worked OK although I should have really looked at the heater chain to ensure optimum working.

30th Jan 2006, 9:54 pm	#7
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Hard to find valve substitutes the prototype of my one chip one valve radio(i promise i will wright this little set up one day) used a pcl83 as its output, basicaly the whole set used junk from the scrap plie it used two 12.5v transformers one 600ma one 300ma the 600ma one was conected to mains like normal with the valve filament conected to the transformers secondary the secondary of the 300ma transformer was then conected in paralell and the primary prodused about 220v ac after rectification and smoothing we had 200v for the HT. must admit though in the end i used an ecl80 and an normal transformer 6v + 200v from a scrap tape recorder due to space restraints Jay

30th Jan 2006, 10:53 pm	#8
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Hard to find valve substitutes Quote: I remember that Sir Douglas Hall published a circuit in Radio Constructor of a hybrid amp which used one of these transfomers with a PL82 Is this the one? http://sites.ecosse.net/Vac.Repairs/...or/circuit.jpg

5th Feb 2006, 3:28 pm	#9
quantum Retired Dormant Member Join Date: Mar 2003 Location: Birmingham, West Midlands, UK. Posts: 785	Re: Hard to find valve substitutes Yes, that's the one. I did think about making it once but never got around to it. It fascinated me that you would still get useful amplification from a PL82 even with such a low HT...