As soon as the CHM allowed us into the new Exhibits Work Room, Ron Williams, Bob Erickson, Bill Newman, Glenn Lea, and Stan Paddock started to organize the room and continue work on Bob Erickson's Williams Tube project.
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The following account starts at 12:30, the time I showed up. At that time, it
appears the group had already decided on how to connect to the memory drawer
(pins left over from the typewriter project), and were getting some wiring on
those connections. Most connections are using the pins, but we did have to
solder to one of the large ground stakes on the rear connector. (Bob, Ron W,
Glen, Dave, Stan)
We got the memory drawer working with Robert's power
supply. That supply claims to have a bias supply that goes to -100V, but it
really goes to -250V, which is just what we needed. With what appears to be
three 807 output tubes it regulates just fine! The pins on our connections to
the filament lines had to be tightened up to get the voltage drop out, and
things started to work. Robert's supply worked great all afternoon. (Bob, Ron
W., Glen, Dave, Bill)
We found the gain through the unit is about 20000
and it picks up the LO of an AM radio just fine. Using the radio we were able
to induce a 5mV PP signal on the input lead, which caused a 100V PP signal at
the output of the video amplifier. We'll see if we can get down to 10uV with
the shields on later. (Bob, Ron W, Ron C, Dave, Bill)
We were all amazed
that the video amp can do a broadband gain (well for the day it was broadband,
100kHz to 1.2mHz) of 20k without oscillating, especially with the covers off.
With no AM radio near by (within 2" of the pickup wire), the amplifier picks up
KGO (K G(eneral Electric) O(akland), 810kHz, 50kW, by Dumbarton Bridge) just
fine. The amplifier pickup wire probably has about 2 mV of KGO on it (why we
need the shields). (Bob, Ron W, Ron C, Dave, Bill)
We lost one of the
drawer electrolytics (Dave yelling "smoke!" was extremely helpful...) for which
I just happened to have a replacement. The replacement was installed and we
were back in business. The clipper seems to work (tube 6 - a 6AS5, which we
could swear is not the right tube). Loss of only one electrolytic on a 60 year
old piece of electronics seems pretty good, although we really don't know if any
of the remaining electrolytics do any filtering! (Bob, Ron W., Dave,
Bill)
We added another tube to the chain, (tube 7, a 6AU6) which does
something, but we are not sure if it is the right thing yet. (Bob, Ron W.,
Bill)
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| Signal picked up from a local transistor radio |
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| Bob Erickson said "Of course it works, what did you expect?" |
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