On Sat, 29 Nov 2014, Barry OGrady wrote:
On Fri, 28 Nov 2014 15:00:46 -0500, Michael Black
wrote:
On Fri, 28 Nov 2014, wrote:
In rec.radio.amateur.boatanchors gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?
As the regulators are potted in and would be difficult to remove, and
since LED's run on voltages on the order of 2-3 volts, no.
How many 3 volt valves can you name?
I think that point was that if a regulator was used to drop the line
voltage to those 3volts, it could handle high voltage input. The probably
false assumption is that the regulator would be variable from some very
high output voltage to some very low output voltage, so one could use it
for tubes by making that adjustment.
A lot of IC regulators can't handle high voltage. If nothing else, nobody
saw the need, it was the solid state age. So dissipation issues aside,
most regulators expect at most a relatively low DC voltage input.
Of course, one can run tubes on low voltage. The Collins 75S receiver
line apparently kept plat voltage relatively low (somewhere around 120v if
I remember right) which had certain advantages. One can run regular tubes
at 12VDC on the plate, there were some articles in Popular Electronics
about this, calling them "starved circuits". Or there were those tubes
designed to run off 12VDC for those hybrid car radios, a last gasp before
transistors took over completely.
I had a hybrid car radio with four valves and two transistors.
The RF amp, mixer, IF amp, and first audio used valves.
Those valves had 12 volts on the plate.
I assumed all the audio would be transitorized. But it was right at that
point where transistors might not have yet been so good at higher
frequencies, so tubes handled the radio part of the radio.
Motorola had a hybrid "lunchbox" type transceiver. A diode mixer in the
receiver, if I'm remembering right, the local oscillator chain was
subminiature tubes, as well as the first IF, then a 455KHz transistorized
IF strip and solid state audio. They had to keep the tubes because the
transistors weren't good enough for VHF.
I also had a valve test oscillator that ran off a 9 volt grid bias
battery.
Yes, that sort of thing would have been quite handy.
Michael