TheRadioBoard

Hi all,

Thank you for replying to my earlier questions regarding the Negadyn style circuit and it's ability to break into regen oscilation without a feedback / tickler winding. I'm still not exactly sure how one would connect my 1625 into this design in place of the valve types that are depicted in the diagrames that Norm and Co. kindly sent me.
Also if you could let me know the best place, and value, of the regen variable resistor I can start construction and experimenting.

Thanks as always,

Big Bill

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Hi.
I doubt somebody can tell you exact values for circuit.
Here is a book in Russian about transitron oscillators.
http://publ.lib.ru/ARCHIVES/M/%27%27Mas ... 0421.(1961).%5Bdjv%5D.zip

U can find there few circuits for pentodes. Regulation of regeneration u can do by applying negative voltage to the first grid.

Hello Big Bill,

I think that a beam power tube may work in this circuit, if you treat it as a tetrode. Beam power tubes are a bit different from true pentodes, so you may be able to get away with this:



Just treat it as if it has two grids and ignore the internally connected third element. The cathode will need to be connected to one side of the heater, probably the side which goes through the rheostat to the common or '0v' connection. Of course, the 1625 uses 12v on the heater. You may need to increase the B+ voltage above 12v. Below is another example:



Imagine that the connection at pin 7 above is the cathode. Again, while the 1625's heater voltage is 12v, 12v may or may not work on the plate. Experiment to find out what voltage seems to work best for you. I have a 1625 available to play with, but I don't think I have a matching socket around now to experiment with.

The idea is to experiment, and have fun! That's how we all learn.

Norman
KA1GUK

That site doesn't allow deep linking to its images. Here they are, in order:





73,

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