Garage sale find, DeWald AM=FM C800

[old_coot88]

Originally Posted by wa2ise

..this tube is at the bottom end of the string, and I decided to get more current for the 6AL5 heater by having it pass the "plate" current of all the set's B+ load currents. Just like how we have a #47 pilot light in parallel with a 35Z5 heater tap and have enough current to make the voltage across that 6V. So one side of the 6AL5 heater gets the powerline "ground" side, and the other side of that 6AL5 heater becomes the set's system ground. It works, but it does take twice as long for the 6AL5 heater to get fully warmed up as the other tubes in the set.

Verrry cool stroke of Yankee ingenuity there.

[wa2ise]

Originally Posted by old_coot88

Verrry cool stroke of Yankee ingenuity there.

Thanks, but I decided, as I have a ton of mil spec submini tubes, 5647 diodes, to use them instead. These diodes' heaters run at 150ma, and I passed their wire leads thru the tube socket pin holes and soldered those leads to the tube socket terminals. And I didn't have to touch the alignment, as the FM detector zeros out nicely (a ratio detector).

I also had to replace the old power cord. But I used a 3 wire flat cord like the original, except the color was different (it was a power cord for an electric lawn mower). The center wire of the 3 became the capacitive coupled FM antenna, like what Dewald did.

[Sandy G]

Awwww...Lookit those l'il guys...How CUUUUTE ! (grin)

[wa2ise]

Originally Posted by Sandy G

Awwww...Lookit those l'il guys...How CUUUUTE !

Yes, I have had that thought too. As if some of my 35W4s had kittens or puppies.

I've wondered if this would have been the next step in consumer electronics had transistors never been invented. I did a web page on what a tube AM radio using tubes like these might have looked like http://pw2.netcom.com/~wa2ise/radios/AA5submini.html

[Reece]

I've looked at your web page a lot: full of great ideas. I have some three-wire flat cord off an electric blanket that has been used for a capacitive line-cord antenna, too. Never throw anything away!