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I've bought a three-tube DC regenerative shortwave radio on Ali-Express/China just to try building. As far as I can tell all the parts are here except for one thing. A schematic.

Has anyone tried successfully to put one of these together and if so could you pass on the much needed info?

It has two transformers. I can't find much on google about them, so I am in the dark as to how to wire them and where. The label says 220V to 6V. Who has 220 volts? Is this kit trying to turn 6 volts to 220 or can these be chucked and just use 6V power supply?

If this project is just junk and not worth trying to work out, don't worry, you won't hurt my feelings, but if you know of a worthy DIY shortwave kit, let me know.

supplied transformers

supplied circuit board

tuning pot

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  • \$\begingroup\$ You don't show the tubes or markings on them. But I'd guess that the transformers (or at least one of them) are for the filament voltages of the tubes. So they should be marked with the first digit being "6". You can create your own schematic with some work examining that board in detail. It's painful. But doable. May I assume this for AM/OOK? \$\endgroup\$
    – periblepsis
    Commented Jul 7 at 21:15
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    \$\begingroup\$ "Who has 220 volts" Most of the world, actually. 220 V ± 10% covers pretty much every standard mains voltage other than North and Central America, Japan, Taiwan, and a handful of Pacific island countries. Most notably, it covers the top two most populated countries on earth, which together make up nearly (over?) 50% of the world population. \$\endgroup\$
    – Hearth
    Commented Jul 7 at 21:20
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    \$\begingroup\$ @RickSteiner The 2P2 is a Russian tetrode (RF). The filament is a direct-heated type designed for battery operation and includes beam-forming plates attached to the center of the filament. So there are three wires at the cathode. You can wire them in parallel or series. This means 1.2 VAC or 2.4 VAC, depending. The 1B2 is also Russian, is a diode (detector, likely) and a pentode (audio amp) and uses 1.2 VAC filament voltages. The filaments are wired in series and it really should be 6.0 VAC and not 6.3 VAC as often found with RCA tubes, for example. \$\endgroup\$
    – periblepsis
    Commented Jul 7 at 21:45
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    \$\begingroup\$ If you connect both transformer primary windings to 110 V they both will provide 3 V at the secondary side. You can connect the secondary windings in series to get 6 V. At wrong polarity the voltages subtract to zero. If so, swap the wires of one winding. \$\endgroup\$
    – Jens
    Commented Jul 8 at 0:47
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    \$\begingroup\$ The ratings on the transformers are misleading. One "transformer" is actually used as a choke and the other is used as an impedance matching matching (output) transformer for the loud speaker. The radio is powered only by batteries. Source: youtube.com/watch?v=wuK_Fl88sPU . You find there also a schematic diagram and some pinout information e.g. for the variable capacitor. \$\endgroup\$
    – 6v6gt
    Commented Jul 8 at 9:04

2 Answers 2

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I think I may have found a site that shows this schematic:

enter image description here

There are two transformers shown, too. This may be a fit, but you will need to decide that. This is the only 3-tube schematic I could readily find. If nothing else, it may help with the transformer situation.

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  • \$\begingroup\$ I've found that also. Only issue is that nothing on that schematic corresponds to the pcb supplied. \$\endgroup\$
    – Rick Steiner
    Commented Jul 8 at 22:26
  • \$\begingroup\$ @RickSteiner Thanks for letting me know and I'm sorry to hear it's no help. (It did match on the two transformers thing, which was slightly encouraging.) That was my best shot. At least I gave it a whirl. ;) \$\endgroup\$
    – periblepsis
    Commented Jul 8 at 23:34
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The ratings on the transformers are misleading. One "transformer" is actually used as a choke and the other is used as an impedance matching matching (output) transformer for the loud speaker. The radio is powered only by batteries. Source: youtube.com/watch?v=wuK_Fl88sPU . You find there also a schematic diagram and some pinout information e.g. for the variable capacitor. – 6v6gt

This is as correct as you get. Thanks 6v6gt!

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  • \$\begingroup\$ You really haven't answered the question. \$\endgroup\$
    – StainlessSteelRat
    Commented Jul 9 at 5:27

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