Discussion in '"Boat Anchor" & Classic Equipment' started by K9VKY, Jul 4, 2021.
Thanks for the reply, I'm quite relieved . Brian
I wouldn't worry about thorium found in any vacuum tube. Once had a pound of thorium oxide in my chemical lab for several years. Only requirement was to post a radio active sign on the storage cabinet. Thirty years later I am still alive and well with no adverse effects. And no I don't glow in the dark.
As a kid back in the 1950s I frequently drove on US Route 89A highway in Arizona through a thick yellow dusk cloud emitted from a nearby uranium processing plant where they produced yellow cake from mined ore. The bushes and rocks in the area were covered with yellow dust. The leftover ore crushings were even once used to make cinder blocks for residential houses.
No one worried much about radio activity back in those days. The only objective was to produce thousands of A bombs. Then it was discovered that the uranium miners were coming down with lung cancer from radon exposure and more care was taken to establish government regulations concerning radioactive exposure.
Many thanks for the details easing my mind!
@K9VKY - do you need a replacement 0C3/VR-105?
No, Jim, but many thanks for the offer. You're to be complimented on your perpetuation of the "ham spirit" from years gone by. Brian K9VKY
OK no problem.
I have...."some"....VR tubes....
73 de Jim, N2EY
The regulation job of the old gas discharge voltage regulator tubes has been completely replaced by Zener diodes.
Not here at N2EY.
The Southgate Type 7 has 6 VR tubes in the power supplies, all octals.
In the receiver/tx mixer supply, a series string of a 0A3 and oC3 gives regulated 75 and 180 volts.
In the transmitter power supply, a differential circuit using a 0C3 and 0D3 gives regulated 45 volts for the 807 grid bias, and a series string of two 0D3s gives regulated 300 volts for the 807 screens.
In both supplies the jumpers in the bases of the VR tubes are all wired in series so that if a VR tube isn't in its socket, there's no B+.
Decades ago, I haywired together a VR tube tester. It's very simple, yet gives a clear picture of VR characteristics - striking voltage, voltage at any current from 5 mA to 40 mA.
I found testing to be important because some VRs provide amazing regulation over the current range - you can go from minimum to maximum current and the voltmeter needle doesn't move a bit. Others aren't so good. Also, some are dead on the marked voltage, others not so much. Yet they all light up and test "good" on a conventional tester.
Between the 866As and the VR tubes, there's quite a light show here.
73 de Jim, N2EY