[Arny Krueger]

"Peter Wieck" wrote in message

On Dec 1, 8:29 am, "Arny Krueger"
wrote:
"Peter Wieck" wrote in message



a) The 300B (or any of the 300-series tubes in any case)
weren't used in Telephoney.

Actually they were. I've scrapped out enough obsolete
telephone equipment to know that they were used for
output stages in drivers for long lines, and also as
voltage regulators in power supplies.

They were used in audio
recording and playback applications for moving pictures
- and again, 10%+ distortion in actual use was neither
unexpected nor unacceptable.

Ever hear of inverse feedback? The good news is that
Bell labs did, and applied it to their equipment.

Sure they did - they called it "negative feedback" and I
believe they patented the process initially. And for
long-lines they may have used the 300s for amplification
- although all the literature I saw pointed towards the
101 series for that purpose - and in one case
specifically excluded the 300 as "not suitable for the
intended purpose" - and as I dimly remember based on the
high voltages required. Do you have any specific pointers
to the 300 used that way? I have always been curious as
to how *few* tubes were used in telephoney - primarily
only used for long lines and undersea cables as
amplifiers and repeaters.

Learn something new every day, I hope.

Check the archives of schematics of WE electronics of the 30s through 50s
and there should be some devices that are obviously booster amplifiers for
long lines - 600 ohms in, 600 ohms out, lots of guts. I saw the things up
front and personal in the scrap piles and surplus sales of the 50s and 60s,
but didn't take names and numbers.

I also have seen some references to special high-reliability 300Bs used as
booster amplifiers in the early transoceanic cables, say from the 30s. I
did some checking around and could only find specific references to the
cables they laid in the 50s, which used physically smaller pentodes.

The power supplies of the AN/MPQ 34 and AN/MPQ 36 radars I worked on in the
late 60s used 300Bs for series regulators for the B+ supplies all over the
radar (3 total power supplies, about 6 RU each). I think there were 8 300Bs
per unit.