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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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25th Dec 2008, 12:37 pm | #1 |
Retired Dormant Member
Join Date: Aug 2008
Location: Bellac, 87. France.
Posts: 357
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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.
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25th Dec 2008, 7:19 pm | #2 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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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 |
Retired Dormant Member
Join Date: Aug 2008
Location: Bellac, 87. France.
Posts: 357
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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?
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28th Dec 2008, 7:40 pm | #4 |
Retired Dormant Member
Join Date: Dec 2008
Location: Garforth, West Yorkshire
Posts: 26
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Re: What was this project?
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28th Dec 2008, 8:07 pm | #5 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
Posts: 2,573
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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 |
Octode
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
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Re: What was this project?
yes please
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29th Dec 2008, 6:53 pm | #7 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
Posts: 2,573
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Re: What was this project?
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 |
29th Dec 2008, 10:16 pm | #8 |
Retired Dormant Member
Join Date: Aug 2008
Location: Bellac, 87. France.
Posts: 357
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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.
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31st Dec 2008, 8:56 am | #9 |
Retired Dormant Member
Join Date: May 2008
Location: Ellesmere, Shropshire, UK.
Posts: 188
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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 |
Octode
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
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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 |
Retired Dormant Member
Join Date: Jan 2009
Location: Wanganui, New Zealand
Posts: 1
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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 |
Pentode
Join Date: Mar 2008
Location: Wigan, Greater Manchester, UK.
Posts: 163
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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 |
Retired Dormant Member
Join Date: Mar 2009
Location: San Francisco, USA
Posts: 7
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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.
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25th Mar 2009, 7:36 pm | #14 |
Rest in Peace
Join Date: Jul 2006
Location: Somerset, UK.
Posts: 2,356
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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
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