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PostPosted: 17 Jun 2014, 19:57 
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Joined: 17 Jun 2014, 14:49
Posts: 11
I want to build a one or two tube radio, using parts that are in an old semi junk marker generator.
Available, two 12au7 tubes and one 12ax7 tube.
I have variable capacitors, an assortment of small ones. I can wind a coil or two.
My thought is an RF amp and a regen detector, and a stage of audio.
I built a one tube receiver back in 53 or 54, and then a project radio soon after, from a popular mechanics or popular science magazine
the project used 3 tubes, as I recall, a detector, an audio output and a rectifier.
Had plug in coils to change bands
I had a lot less knowhow on troubleshooting back then, and it never worked.
May have been a bad filament in the 35z5 it used as rectifier, I know that now.
used a50l6gt for audio, and a 12 volt filament triode of some kind that was common way back.

I know tons more now, having held a commercial radiotelephone, 2nd class, then general class, and now hold a general class amateur radio license.
And can troubleshoot.
I know the two basic kinds of regen detectors, but don't recall the values of parts at this time.
I am limited in parts, especially resistors, other than a decent assortment of 1/4 watt resistors.
I want to use a 600 ohm headset, being as i have a number of them that seem to all be in good condition. Were ones tossed by a local school. I need a few pointers on this part, as well as resistor values, and coupling caps.
I do have a drawer full of ceramic disc caps, don't recall the value, don't feel like going to check now, but should do well
the old generators as power supply should serve well.
I know one can sub parts, and use parallel parts in some instances.
if someone can help with a few schematics, would be very thankful.
I am limited in getting parts, due to little income, and being a long ways from suppliers, not to mention rather disabled due to COPD.

Anyways, I could possibly design something by trial and error, just not up to it a lot of the time.
One nice thing with tubes was having a lot of leeway to work with.
Antenna no big deal, as I have a dual dipole antenna for 75 and 160 meters, which will also do well for AM broadcast.
Can also run an end fed wire if needed...

I could use some parts like 9 pin mini tube sockets, rather than trying to use the existing PCB in the generator, as the ones in it are not located in ideal spots. But I could try and salvage some from a junk AC/DC radio...


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PostPosted: 21 Jun 2014, 16:13 
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Joined: 14 Feb 2010, 13:13
Posts: 663
Location: Lisbon, Portugal
Hi!

I guess I can help you.

You are looking for a receiver with only a few tubes, so in order to keep it simple, the nearest approach is a super-regenerative type.

What bands would you like it to cover?

Do you also require single sideband?


73 de Miguel

CT2JUT @ IM58KQ


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PostPosted: 21 Jun 2014, 19:18 
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Joined: 17 Jun 2014, 14:49
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I have done some searching, and coming up with some schematics.
What I want is the standard AM broadcast band, 540-1600Khz, and possibly 75 and 40 meters.
Would love to use plug in coils, but I have neither sockets or plug in forms.
Bandswitch is also something I may not have. have to really hunt through a lot of boxes never unpacked.

Now, I want to use a simple regenerative detector, grid leak type, not a super regenerative.
I live well away from most cities, so local stations do not becomes a problem.
Thirty miles from the closest place that has a broadcast station. Not sure if there is a regular AM broadcast station there or not, though it should be no problem if there is.

I did build one that received AM broadcast back in the early 50's, using an older type triode tube I had, and it did work.
Been so many years now.

SSB is no problem, though selectivity on a busy band might be a bit of a problem.
Never tried listening to SSB with a simple one or two tube receiver.
For serious amateur radio SSB, I simply use my Icom 706 MK II G.

I am looking for nostalgia mostly, and want to use as much as I can from what I have available to salvage.
I read that 35MM plastic film cannisters do nicely as coil forms.
I do have some magnet wire, but am not sure what gauge it really is.
But should work well for winding coils


Wayne WA2YNE
Imperial Texas


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PostPosted: 21 Jun 2014, 21:42 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
WA2YNE wrote:
Never tried listening to SSB with a simple one or two tube receiver.


Direct conversion! :D

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 21 Jun 2014, 21:53 
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Joined: 17 Jun 2014, 14:49
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I should add here, I have some parts in the marker generator that I will use as a basis, that I can salvage.
Including a 1.1 Megohm and a 2.2 megohm resistor(s).
A number of others, and capacitors I can salvage.
Transformer for power, 120 VAC input, a 6.3 VAC secondary, and a B+ winding.
has a single diode rectifier, I prefer to change that to a full wave bridge.
is probably about 125 to 150 volts, using full wave bridge make filtering easier

I have a bunch of small variable capacitors that I can use, all more than adequate for the need. The case will need a few holes made, maybe, and I should maybe change the line cord to a 3 wire with ground, as a safety feature.
Mounting tuning capacitors should be simple, using parts I have on hand.
I used to be in the repair business, TV, radio, and more.
Just trying to refresh my memories to be able to do the circuits so they work right the first time.
may need to make some kind of shaft extension for the tuning and regen control caps.
Don't have a huge junk box like I used to have...
Will take a few pix of the box as it is, and after I modify the parts inside.
Try to post once I do, and edit them, as my pix tend to be rather big.

Reading another post, I am not sure I want to make a direct conversion unit at this time.
I want to do a regenerative detector for now.

Wayne WA2YNE
Imperial Texas


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PostPosted: 22 Jun 2014, 04:05 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
WA2YNE wrote:
....as my pix tend to be rather big.


Here's a gorgeous, lightweight tool to tweak images without a full blown manipulation proggie...

http://www.xnview.com/en/

Cheers!

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 22 Jun 2014, 06:11 
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Joined: 14 Feb 2010, 13:13
Posts: 663
Location: Lisbon, Portugal
Hi Wayne!


I believe you´re looking for something like this:

http://www.ohio.edu/people/postr/bapix/Regen_HB.htm

Seems to be an excellent startting point! :)



Cheers!


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PostPosted: 22 Jun 2014, 10:51 
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Joined: 04 Jun 2008, 20:59
Posts: 3814
Location: Arizona, USA
Hi, You can sub many tubes for the ones in that circuit. Pretty much any pentode for the 6V6 (a 6AQ5 would be a natural but others would be fine) and a 12AU7 for the 6SN7. I would Google regenerative radio receiver schematics and see what turns up. There are many.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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PostPosted: 22 Jun 2014, 18:54 
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Joined: 17 Jun 2014, 14:49
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Okay, a few things to point out.
Other than a semi junk AC/DC 5 tube AM broadcast radio, the usual 5 miniature tubes, including 50c5 and so on, I have only the 2 dual triodes.
The case I will be using has the 3 triodes and sockets.
I only need to use one tube, most likely in socket near the front of the chassis.
Remove parts to only feed power to where I need it.
I have a number of assorted small variable capacitors, but shafts small for most knobs.
One has a part on the shaft that might work for a larger knob. I have few knobs available, other that what I might salvage from other gear.
I could glue/epoxy a disk to one to put marks on. I could make it so I use a main tuning capacitor, and a fine tuning capacitor.
Adjust that using an adjustable trimmer cap.
I have two magnet coils that have enough magnet wire on them to wind a number of coils.
Unknown the size. Way back I simply bought a couple of spools of wire, known sizes marked on the spools.

I could use either a tickler coil, as it was called, in the plate circuit, or a tapped coil using cathode feedback.
The radio I built in the early 50's used the plate coil.
Coil was hard wired, not plugged in.
Of course, I cannot recall what tube it was, other than it being an older 5 pin triode.
Since my original post, I did find many assorted circuits.

I do need to taker some voltage readings, to see what is available from the power supply portion of the marker generator that will be partly stripped and redone for this project.
Far safer than direct rectifying from the AC main, as was done in AC/DC radios. Those tended to have a possible shock hazard if not plugged in right, and/or a part failed.
I have seen minor leakage from some cheap solid state devices that used a transformer, but not an adequate ground.
Polarized plugs help, unless someone made an error in wiring the outlets.
Three wire grounding is far better, though I have seen people break off the grounding pin to use an older outlet..


Wayne WA2YNE
Imperial Texas


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PostPosted: 29 Jun 2014, 19:54 
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Joined: 17 Jun 2014, 14:49
Posts: 11
trying to figure out how to determine the size of the magnet wire I have, which is wound on two magnet cores.
All I am sure of its that is at least #22, maybe 24 or 26..
I don't have any wire gauges handy, and the drill gauges I have are of no help, not fine enough.
I have started removal of part from the unit that will become the radio.
And while looking at other circuits, I saw where a 6.3 volt filament transformer got used as an audio output to 8 ohm speaker.
Should work with 600 ohm headphones.
I have some older high impedence headphones, but they need to be rewired.
Not to mention some padding for my ears. My good headset needs new wire and the foam padding has gone bad.
They were new back in 97 or 98, were still doing well till mice got into things and chewed wires here and there.
But I have a number of 600 ohm headsets, mono, that I saved from the dump.
Seems the school system will toss older stuff, rather than contribute it to anyplace.
As a teen with little money to spare, I used to salvage old unused stock that was tossed out by a parts store.
had a lot of potentiometers and parts back then.
Even salvaged batteries.
Some you could take apart and save the good cells, and many used cells the same size as AA cells.
I am still undecided on the exact detector circuit, but I want to use a plate tickler, and an antenna winding too, with a trimmer...
I did find a photo editing program called Fotoxx, that will let me edit and save as to smaller sizes.
pictures to follow before long.
Schematic I can't draw right. I can by hand, but do not have a working scanner right now.
Need electronics symbols to do on the computer.


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