J
John Crighton
Guest
Hello All,
I have an old HP411A RF millivoltmeter that I would like
to restore to working condition. I don't know much about
this unit apart from what I can see. Very nicely constructed,
in the 1960s or earlier I am guessing, Mainly toobz and two
transistors, everything is getatable. There is a slow speed
motor turning a disc with some light bulbs shining on the disc
and two long clear plastic rods to conduct light to some sort
of light sensing unit. A device to make a chopped signal to
be AC amplified, I am guessing.
The instrument sounds good with the motor gently turning,
filaments glowing, and has that nice warm smell also. I like it!
The sort of instrument that makes you feel like you are getting
your monies worth.
Unfortunately, without a working RF probe the instrument is
useless so I am looking for information on the probe. I am
guessing it uses a semiconductor diode (not a valve) in the
probe assembly, since the maximum voltage that the
instrument can measure is only 10 volts.
I am looking to buy bits and pieces for the probe assembly
or even a complete working unit with a good probe.
A long shot, I know but I have to ask.
Regards,
John Crighton
Hornsby
I have an old HP411A RF millivoltmeter that I would like
to restore to working condition. I don't know much about
this unit apart from what I can see. Very nicely constructed,
in the 1960s or earlier I am guessing, Mainly toobz and two
transistors, everything is getatable. There is a slow speed
motor turning a disc with some light bulbs shining on the disc
and two long clear plastic rods to conduct light to some sort
of light sensing unit. A device to make a chopped signal to
be AC amplified, I am guessing.
The instrument sounds good with the motor gently turning,
filaments glowing, and has that nice warm smell also. I like it!
The sort of instrument that makes you feel like you are getting
your monies worth.
Unfortunately, without a working RF probe the instrument is
useless so I am looking for information on the probe. I am
guessing it uses a semiconductor diode (not a valve) in the
probe assembly, since the maximum voltage that the
instrument can measure is only 10 volts.
I am looking to buy bits and pieces for the probe assembly
or even a complete working unit with a good probe.
A long shot, I know but I have to ask.
Regards,
John Crighton
Hornsby