What was this project? - UK Vintage Radio Repair and Restoration Discussion Forum

humphrey · 25th Dec 2008, 12:37 pm

I was given a box of bits which included a board with two HL2K and one KT24 valves mounted on it. I was wondering what it could have been for.

Heatercathodeshort · 25th Dec 2008, 7:19 pm

Hello Humphrey,
Probably a valve amplifier for battery use, maybe for gramophone use in a rural area with no mains supply. The HL2's are general purpose 2volt battery triodes. The KT24 is a 2volt battery output beam tetrode that will deliver around 600m/w with 150v on its anode. Regards, John.

humphrey · 27th Dec 2008, 12:33 pm

I just had a follow up. It seems to have been a vintage radio project that was in May/June 1980 Practical Wireless. Any ideas for making the horn speaker?

harrym1byt · 28th Dec 2008, 7:40 pm

Quote:

Originally Posted by humphrey

I just had a follow up. It seems to have been a vintage radio project that was in May/June 1980 Practical Wireless. Any ideas for making the horn speaker?

Weren't some of them made from papier mache, dried painted and then varnished?

KeithsTV · 28th Dec 2008, 8:07 pm

The pictures in the two PW articles show a horn speaker with a a circular profile but the construction instructions show a square cross section horn. Does anyone want to see the articles?

Keith

Trevor · 29th Dec 2008, 1:56 pm

yes please

KeithsTV · 29th Dec 2008, 6:53 pm

Here's the article plus the cover of the May 1980 issue with a picture of the set.

Some parts of the diagrams were in a light colour so some of the assembly drawings appear to have bits missing.This is because I scanned in B&W rather than greyscale to keep the file size to fit in with the limits.

If anyone wants greyscale or colour copies PM me know and I'll rescan and send by email.

Keith

humphrey · 29th Dec 2008, 10:16 pm

The difficult bit is making the horn. I have been thinking about it for a few days and my latest idea is making a wire former for applying the gummed paper strips. Starting with a trumpet shape (vase/bottle), wound with wire and soldered together on the desired inner curve. I leave the rest to the imagination.

Antlong · 31st Dec 2008, 8:56 am

Hello Humphrey et al,

Might it be easier to make a former of plaster of paris or some such, then coat it with papier mache? That also has the advantage of repeatability - a whole new cottage industry!

Happy New Year -

Regards Ant

Trevor · 31st Dec 2008, 1:30 pm

I think a wood /plaster mould is a good idea ! Then make the horn out of fibre glass ?
regards Trev

PioneerbwZL2CDH · 2nd Jan 2009, 2:00 am

Hello all,

I built this project about twenty years ago, but using 100v supply to type 76
tubes, with seperate matching mahogany cabinet for power-supply. Major
disadvantage was the high voltage to open terminals on front panel (and the
existence of numerous small children in the house). Worked satisfactorily, but
I wasn't entirely happy with results.... looked great in the lounge, but not
really ideal for listening to all evening.
The children problem cured itself with the passage of time, however has
recurred with occasional visits of miniatures of originals.

Am presently building another of this project, using 30's for detector and amp,
and 33 for output tube. Building in teak cabinet, with teak former for coils on
top of unit. Additionally, in my original as well as current project, I continued
the 'stick' upon which the moving coil pivots through to underside of cabinet to
enable the coil to be controlled by a knob in the diagonally opposite corner of
the front panel. This cured the problem of hand-capacitance affecting the coil
during adjustment.....
Am also building battery eliminator in main cabinet using VR105 (OC3) 'A' battery
is a 2v glass cell from a telephone exchange. 'C' battery from 11x1.2v AA NiCad's.

Was fortunate in locating on TradeMe (local version of e-bay) an old horn speaker
of 1923 vintage, British Thomson-Houston make, minus its base and speaker. I
laminated and turned a mahogany base to match the old BTH base, and inserted
an ordinary 8 ohm speaker. Repainted in as near the original BTH colours as I could
and having new BTH transfer printed to remount on horn.

Am not very computer literate, but if anyone interested in my modified circuit, let
me know, and will try to forward it or any other detail.

Compliments of the season to all
regards
Nigel

Baggrus · 25th Feb 2009, 4:06 pm

Very interesting project. Reminds me of my early experiments with valves and parts from the tip and a 30's constructors book.

I got to thinking about a driver for the horn speaker, and realising how small the 20's drive units were for these something dawned on me. There is a suitable tiny speaker fitted to computer motherboards. Farnell used to stock them as well.. first item on the speakers page in my 1990 book. Small tubular little black thingy. I must have a heap of them on scrap boards. I will investigate further because they look to be just the job for authentic looking small throat horns..

ryanflannery · 10th Mar 2009, 5:45 am

Why dont you go to a flea market and buy an old horn and alter it? There are a lot in poor condition that sell for 10 to 20 bucks.

chipp1968 · 25th Mar 2009, 7:36 pm

I remember that ,I remember a School freind made the square horn . didnt look that good . I would get a real one .But If you wanted to make one , what about cutting the flared petal sections from card ,taping together then coating that with papermache or fiberglass . You could do the flare seperately to the swan neck

25th Dec 2008, 12:37 pm	#1
humphrey Retired Dormant Member Join Date: Aug 2008 Location: Bellac, 87. France. Posts: 357	What was this project? I was given a box of bits which included a board with two HL2K and one KT24 valves mounted on it. I was wondering what it could have been for.

25th Dec 2008, 7:19 pm	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: What was this project? Hello Humphrey, Probably a valve amplifier for battery use, maybe for gramophone use in a rural area with no mains supply. The HL2's are general purpose 2volt battery triodes. The KT24 is a 2volt battery output beam tetrode that will deliver around 600m/w with 150v on its anode. Regards, John.

27th Dec 2008, 12:33 pm	#3
humphrey Retired Dormant Member Join Date: Aug 2008 Location: Bellac, 87. France. Posts: 357	Re: What was this project? I just had a follow up. It seems to have been a vintage radio project that was in May/June 1980 Practical Wireless. Any ideas for making the horn speaker?

28th Dec 2008, 8:07 pm	#5
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,573	Re: What was this project? The pictures in the two PW articles show a horn speaker with a a circular profile but the construction instructions show a square cross section horn. Does anyone want to see the articles? Keith

29th Dec 2008, 1:56 pm	#6
Trevor Octode Join Date: Aug 2006 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 1,082	Re: What was this project? yes please

29th Dec 2008, 10:16 pm	#8
humphrey Retired Dormant Member Join Date: Aug 2008 Location: Bellac, 87. France. Posts: 357	Re: What was this project? The difficult bit is making the horn. I have been thinking about it for a few days and my latest idea is making a wire former for applying the gummed paper strips. Starting with a trumpet shape (vase/bottle), wound with wire and soldered together on the desired inner curve. I leave the rest to the imagination.

31st Dec 2008, 8:56 am	#9
Antlong Retired Dormant Member Join Date: May 2008 Location: Ellesmere, Shropshire, UK. Posts: 188	Re: What was this project? Hello Humphrey et al, Might it be easier to make a former of plaster of paris or some such, then coat it with papier mache? That also has the advantage of repeatability - a whole new cottage industry! Happy New Year - Regards Ant

31st Dec 2008, 1:30 pm	#10
Trevor Octode Join Date: Aug 2006 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 1,082	Re: What was this project? I think a wood /plaster mould is a good idea ! Then make the horn out of fibre glass ? regards Trev

2nd Jan 2009, 2:00 am	#11
PioneerbwZL2CDH Retired Dormant Member Join Date: Jan 2009 Location: Wanganui, New Zealand Posts: 1	Re: What was this project? Hello all, I built this project about twenty years ago, but using 100v supply to type 76 tubes, with seperate matching mahogany cabinet for power-supply. Major disadvantage was the high voltage to open terminals on front panel (and the existence of numerous small children in the house). Worked satisfactorily, but I wasn't entirely happy with results.... looked great in the lounge, but not really ideal for listening to all evening. The children problem cured itself with the passage of time, however has recurred with occasional visits of miniatures of originals. Am presently building another of this project, using 30's for detector and amp, and 33 for output tube. Building in teak cabinet, with teak former for coils on top of unit. Additionally, in my original as well as current project, I continued the 'stick' upon which the moving coil pivots through to underside of cabinet to enable the coil to be controlled by a knob in the diagonally opposite corner of the front panel. This cured the problem of hand-capacitance affecting the coil during adjustment..... Am also building battery eliminator in main cabinet using VR105 (OC3) 'A' battery is a 2v glass cell from a telephone exchange. 'C' battery from 11x1.2v AA NiCad's. Was fortunate in locating on TradeMe (local version of e-bay) an old horn speaker of 1923 vintage, British Thomson-Houston make, minus its base and speaker. I laminated and turned a mahogany base to match the old BTH base, and inserted an ordinary 8 ohm speaker. Repainted in as near the original BTH colours as I could and having new BTH transfer printed to remount on horn. Am not very computer literate, but if anyone interested in my modified circuit, let me know, and will try to forward it or any other detail. Compliments of the season to all regards Nigel

25th Feb 2009, 4:06 pm	#12
Baggrus Pentode Join Date: Mar 2008 Location: Wigan, Greater Manchester, UK. Posts: 163	Re: What was this project? Very interesting project. Reminds me of my early experiments with valves and parts from the tip and a 30's constructors book. I got to thinking about a driver for the horn speaker, and realising how small the 20's drive units were for these something dawned on me. There is a suitable tiny speaker fitted to computer motherboards. Farnell used to stock them as well.. first item on the speakers page in my 1990 book. Small tubular little black thingy. I must have a heap of them on scrap boards. I will investigate further because they look to be just the job for authentic looking small throat horns..

10th Mar 2009, 5:45 am	#13
ryanflannery Retired Dormant Member Join Date: Mar 2009 Location: San Francisco, USA Posts: 7	Re: What was this project? Why dont you go to a flea market and buy an old horn and alter it? There are a lot in poor condition that sell for 10 to 20 bucks.

25th Mar 2009, 7:36 pm	#14
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: What was this project? I remember that ,I remember a School freind made the square horn . didnt look that good . I would get a real one .But If you wanted to make one , what about cutting the flared petal sections from card ,taping together then coating that with papermache or fiberglass . You could do the flare seperately to the swan neck