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Old 19th Apr 2014, 2:41 am   #61
julie_m
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Thumbs up Re: Building a Radio from Junk

This is great -- proper Zombie Apocalypse Survival stuff!

Have you had a word with Our Man in Havana? Forum member Miguel Lopez has built desoldering guns and used reclaimed solder, with crushed-up aspirin tablets for flux!

If I needed to make a log pot from scratch, I'd probably build a stepped control; something similar to an old-fashioned motor controller, with a contact sliding over a ring of studs linked by resistances. I could then use longer and longer lengths of thinner and thinner wire between each stud and the next.
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Old 19th Apr 2014, 3:29 am   #62
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Default Re: Building a Radio from Junk

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Originally Posted by echelon View Post
This project strongly reminds me of the WW2 Colditz/Stalag Luft prison camp radio designs, but with a modern-day/steampunk update.
What about a Mamod static engine for generating the HT via a dynamo, to give you a meths-powered MF rx? As long as the spark QRM was minimal.

the POW radios are very impressive, this looks to be the most elaborate, I can learn a lot that will be useful for this build from them, I have it so much easier, no guards, a choice of valves, and access to vast info from the net and my old books, and a good source of junk to be reused!

years ago I built a simple 1 valve non regen radio with a battery valve maybe an 1s4? it worked very well, when I was showing it at the radio club, another member had a steam powered dc motor as a generator, we linked projects, and used his steam engine and dc motor to supply my HT! I think it was 12v, it was not as loud, but still worked well, I had built my head phones made out of old 1980's telephone hand sets and coat hangers, I had styled then on 1920 head phones and where 1.2K!

http://www.wharfedaleobserver.co.uk/...radio/?ref=rss
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Old 19th Apr 2014, 4:15 am   #63
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my first valve radio was based on this 1935 set of plans, I was in college at the time studying IT, I had been given a gray nos cv something RF valve at a audio convention years ealer when at school? I built the radio around that valve it had a heater needing 6.3v 0.3amps, and I think 2ma max emission, I build the octal valve socket on a small flat transparent plastic box, I think I used the wax tape from double sided sticky tape and silver foil for the capasters epoxied in between transparent plastic scraps worked great! the case used old keyboard springs for contacts, and paper clips for the valve base, I did use an air variable capacitor that I got from the radio club, I even built the grid leak resister, and the coil was made of recycled and straitened cat5 cable, but I did not wind it on a card tube, I used a lot or epoxy resin so it was free standing! only the ticker coil was on a bit of loo roil card tube, with a bamboo secure and cork for control, the power supply was a 230 to 6v, and 230v to 12v transformer fed pack to back, so I had 6v ac for the heater and 120v for the HT, I found it worked ok my diy head phones, but the frequency was way to low, probable becos the instructions where so old the used and that part of the broadcast band used had moved and the extra capacitance from all the epoxy on the coil! I also found the HT would very a lot, I got a 4 pin voltage regulator tube and a large electrolytic capacitor, I also had a load of bc108s I had from school, I studied the data sheet, and made a sort of super transistor out of them, I used the valve voltage regulator as my 90v reference like a zener diode and the bc108's as the pass element, it worked great! and with the stabilized power supply the radio was much easier to use, I later built a class A ecl86 based audio amp in a plastic quince jam pot, with the valve and transformer on top, hooked it to the regen and 90v psu, the amps only problem was the transformer was top heavy and I was afraid of breaking the valve when it flipped over! but I just broke the hot glue on the valve base regularly
http://www.vcomp.co.uk/one_tube_1935/one_tube_1935.htm

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Originally Posted by greenstar View Post
That's an ingenious condenser. I saw a similar one in a 1918 magazine. There are also the sliding cylinder and book types:
Both are ingenious ways to build a variable condenser, I will consider if to use ether design, I have seen one like the second variable condenser using coke cans in the web, thanks for the info!
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Old 19th Apr 2014, 5:10 am   #64
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Default Re: Building a Radio from Junk

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Originally Posted by Radio Wrangler View Post
You can use fixed capacitors with variable inductors. See 'permeability tuning' and 'variometer'
For home-made variable caps, try butterfly types to avoid sliding contacts.
I agree electrostatics outside would be a problem... but they sound stunning. Home made headphones article in WW. Not for the faint-hearted.
I had not thought about the capacitors sliding contacts and there problems!
A variometer and fixed capacitors may be the way to go, and could be a lot easier to build! I need to do more research on them, and I did not know about "permeability tuning" but that must be how IF transformers are tuned!

I wound would feel a bit worried at using diy electrostatics headphones, with 2kv or more on the electrostatics headphones! especially in a damp condirions.
the butterfly capacitors look great, but it would waste much more steel when making it
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Old 19th Apr 2014, 5:58 am   #65
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Default Re: Building a Radio from Junk

There are neat permeability tuners in millions of old car radios in rubbish dumps all over the world. Some of them will even have specialised valves for 13.8v HT (Car with engine running battery voltage)

2kV in headphones is safe because of very high impedence and miniscule current. You make more brushing your hair. Look up 'Stax' to see posh commercial ones. They sound gorgeous, but ayeee! the price.

David
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Old 19th Apr 2014, 6:12 am   #66
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Default Re: Building a Radio from Junk

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Originally Posted by ajs_derby View Post
Have you had a word with Our Man in Havana? Forum member Miguel Lopez has built desoldering guns and used reclaimed solder, with crushed-up aspirin tablets for flux!
If I needed to make a log pot from scratch, I'd probably build a stepped control; something similar to an old-fashioned motor controller, with a contact sliding over a ring of studs linked by resistances. I could then use longer and longer lengths of thinner and thinner wire between each stud and the next.
it would be great to use reclaimed solder! especially as lead/tin solder is so expensice and bad for the environment!
using aspirin tablets for flux!! I have google it and its an acid, I vaguely remember acid fluxes where used in the 1920s, but it corroded thin coil wires ect, but my research did uncover how easy it is to make rosin flux from pine tree sap and a solvent! so it looks like I will be taping the sap from some pine trees, and looking for the right type of small bottle. now all I have to do is reform the solder into wires!

there is a lot of old junk I could get solder from, the old car cd player is full of it!

yes I have been thinking about switched resisters or capacitors like you suggested, thanks for the info
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Old 19th Apr 2014, 6:18 am   #67
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Default Re: Building a Radio from Junk

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There are neat permeability tuners in millions of old car radios in rubbish dumps all over the world. Some of them will even have specialised valves for 13.8v HT (Car with engine running battery voltage)
the dumps by me in surrey in the UK now no longer let you get stuff with the new recycling regulations!! sadly
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Old 20th Apr 2014, 2:41 am   #68
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Default Re: Building a Radio from Junk

Well, they can't be sure you're not going to dump something that was last known to be in their possession, illegally out in the countryside somewhere .....

You generally need to have a person "on the inside", in order to get hold of recyclable materials from recycling centres to recycle.

Many cars go for scrap with their radios still fitted, so try a nearby car breaker's. They can have some confidence that you aren't going to be dumping stuff illegally, just because you paid good money for it .....
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Old 24th Apr 2014, 4:40 am   #69
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Default Re: Building a Radio from Junk

Sadly I dont have any one "on the inside" but will be on the lookout for junk in skip ect, that I can use, I am very interested in reusing solder, and will have a go at making flux from pine resin from pine cones! I will be looking for 2 pressure cookers to use!
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Old 24th Apr 2014, 12:56 pm   #70
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Default Re: Building a Radio from Junk

Hi audion_1908, love the project so far. i have literly dozens of scrap AM car radios in my junk room and would be happy to send you a permeability tuner out of one if you would like to have a play with one.

Jay
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Old 25th Apr 2014, 6:02 pm   #71
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Default Re: Building a Radio from Junk

Tip sales no longer, but keep your eyes open for junk tellys. I have rescued a couple from the side of the road for bits - copper wire, regulators, power resistors, not saving a lot of money, but the insatiable desire to take things apart. CRT tv's always at car boots/jumble sales, or from Freecycle, if you wish to recycle solder.
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Old 25th Apr 2014, 7:27 pm   #72
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Default Re: Building a Radio from Junk

Ive often wondered about salvageing the wire from a CRT tv's deflection yoke for home coil winding. not something ive tryed yet but it would yeald a good amound of good quality copper wire.

Jay
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Old 25th Apr 2014, 8:10 pm   #73
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Default Re: Building a Radio from Junk

Hi Jay, sadly it is often heavily impregnated with varnish etc so that it retains its shape and is virtually impossible to unwind. Old mains transformers are a better bet.

Ed
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Old 25th Apr 2014, 8:59 pm   #74
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Default Re: Building a Radio from Junk

Ed, I don't like to contradict you, but I have successfully unwound crt coils. This is what I used for my GEC rf coil repair. I have a spool of such wire. I guess it depends on the set, and I was lucky, but have done so a couple of times. It's a pallaver to get the coils apart, but I found after prising off lumps of goo used to hold windings in place, it was quite possible, if time consuming. Not economic if time is worth anything, but a nice exercise if you like reclaiming. There are traces of varnish left on the wire, so it does not do an entirely neat job.
Photo shows a crystal set coil wound with such wire - my bottle cutting is not perfected.
Tony
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Old 25th Apr 2014, 9:46 pm   #75
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Default Re: Building a Radio from Junk

Hi Tony, I was referring to modern CTV's in general. The older B/W sets should be easier to unwind.

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Old 26th Apr 2014, 8:25 am   #76
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Default Re: Building a Radio from Junk

Hi Ed, all the sets I harvested were 1990's or more recent. I wouldn't want to mutilate an older set if recoverable. But it is awkward, as the windings have dobs of hardened glue keeping them in place. These I find can be prised off with a little care. If a modern CRT tv comes my way - I scrapped my girlfriend's after it failed - I tend to remove the speakers, larger components, and these coils, transistors and regulators, etc, and also can be a useful source of connecting wire. Must stay on topic!
Tony
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Old 26th Apr 2014, 9:05 am   #77
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Default Re: Building a Radio from Junk

Hi Tony, this may be adhesive coated wire; it is wound on a former then a highish DC current is passed that melts the glue and sticks it in place. I thought it was an epoxy, but a may be a form of hot melt. Try a hot air gun to soften and see if it unwinds easier.

Ed
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Old 27th Apr 2014, 1:48 am   #78
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Default Re: Building a Radio from Junk

I will have to look out for dead tv's and monitor's for solder and copper enameled and hookup wire, if the wire is epoxied or glued together and I cannot use it I can take or swap it at the metal merchants.
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Old 7th May 2014, 6:07 am   #79
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I have found 2 sets of 8 ohm speakers in a skip! they are (Toshiba, 3 way high fidelity speaker system, ss-d2) the spider, paper cone and foam looks good, but they have no crossover! only caps in series with the too smaller speakers, but I do now have a 8~inch speakers for free!
any one know where I can get data on them, or know what amp it was used on, age anything?
the label on the speaker is hard to read but I can get F20FC could be HIF20FC and 8(ohm)2CA12 and 1126
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Old 7th May 2014, 6:15 am   #80
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Default Re: Building a Radio from Junk

more speaker pics, I also got some free oak veneered mdf from a different skip! if may be usable for the front!
I have also found a out of date pack of 7 300mg aspirin tablets to try as flux!
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