The magic 1625 valve, two regen radios

[W4HAY]

Hi I checked up with the local electric company and they can't supply enough power to run such a beast

I do however have plans to build a simulated steam powered set as a "joke set"!!! Will that do ?

Sorry to dissapoint you Nick

Steampunk radio! If you could find an old toy steam engine, couple it to a permanent magnet hobby motor for a generator, and use 1.5 Volt tubes like the 1T4, that would work. I've gotten good results with them running about 12 Volts on the plate.

Another thought: I've seen some old code oscillators using a#30 or 1H4 tube with only a 1.5 volt filament battery and no B+. Could this principle be used with an 811? That Thoriated filament really boils off the electrons.

[G0CWA]

Steampunk radio!

All I can say is see my latest post "WHO STOLE MY HT !" I am ahead of you

TTFN Nick

[K7JSW]

I built a regen using a 1625. With 12vdc on filament and plate there wasn't adequate volume for comfortable listening even with high impedance antique headphones. Next I tried 12vac on the filament and higher dc voltage on the plate. Audio output was still low. Got any suggestions other than adding audio stages or external audio amp? 73 John k7jsw

[W4HAY]

...Got any suggestions other than adding audio stages or external audio amp? 73 John k7jsw

Try another tube. The one you have may be weak. Because they were cheap, they underwent a terrible amount of abuse back during the hey-day of converted surplus rigs.

[G0CWA]

there wasn't adequate volume 73 John k7jsw

Hi John

Firstly try another valve, if you have one, as already suggested, if you followed my circuit that is the most likely cause of low volume as mentioned by W4HAY.

The filament can be fed with either AC or DC but this should make no difference to performance.

Can you drive the set into oscillation with the regen control? because low audio gain can also happen if you are too far below the oscillation point.

The set should just be on the verge of oscillation for max volume drive it into oscillation with the regen control and and then back off control till it just stops.
If you can't get it to oscillate three options

1 move the tap feeding G1 via R1/C6 further up the coil
2 increase the value of the feed cap in the pll combination (C6 on my diagram) to around a maximum of 200pF, feeds G1
3 Try another valve

If it oscilates ok check the transformer is connected the right way round (try reversing the primary and sec connections)



If all else fails contact me directly via e-mail at n.strong@hotmail.co.uk and we could set up a skype link and talk directly.

Good luck and hope this helps 73 Nick G0CWA

ps

If you didn't build my circuit but one where you use two coils, a tank (tuning) coil and regen feeback coil, try reversing the connections to the
regen feedback coil, you could have the phasing on the feed back wrong it is very easy to do, I and others have done it many times.

[G0CWA]

Steampunk radio! If you could find an old toy steam engine, couple it to a permanent magnet hobby motor for a generator, and use 1.5 Volt tubes like the 1T4, that would work. I've gotten good results with them running about 12 Volts on the plate.

Another thought: I've seen some old code oscillators using a#30 or 1H4 tube with only a 1.5 volt filament battery and no B+. Could this principle be used with an 811? That Thoriated filament really boils off the electrons.

Hi No B+ ? I'd be interested to see such a circuit how can it work except as a diode?

73 de G0CWA Nick

[KO6WB]

Does sound strange doesn't it? Perhaps the tube enters an area of negative resistance sort of like a tunnel diode does and that causes it to break into oscillation. Could be something worth looking into.
Hey Nick, are you going on to more projects soon?
73
Gary

[G0CWA]

Nick, are you going on to more projects soon? 73 Gary

Hi Gary I've two more posted see my latest post WHO STOLE MY HT .

I also have another in the final throes of being completed and written up, I've only got to calibrate the tuning scale and complete
the write up, rough details are on my last post with a photo of the rats nest prototype.

73 for now Nick G0CWA

[W4HAY]

s

Does sound strange doesn't it? Perhaps the tube enters an area of negative resistance sort of like a tunnel diode does and that causes it to break into oscillation. Could be something worth looking into.
Hey Nick, are you going on to more projects soon?
73
Gary

The tube does have a difference in potential between parts of the filament and the plate. The filaments in both the #30 and 1H4 are in the form of a "V" turned upside down, so one end of it will be negative 1.5 Volts with respect to the plate and this potential difference will vary towards zero along the length of the filament. Thus the average "plate" voltage would be 3/4 Volt.

Back in the '30s, several "starved" circuits were popularized using very low plate voltages.

[K7JSW]

Thanks for the suggestions. Will try a new tube first and go from there....Actually, I have built both versions of the 1625, tickler coil and tapped. Neither one had enuf volume. Perhaps my junk box tubes are soft. Anyway, will take another stab at it and post my results here. Tnx again! 73 John k7jsw