Take a
look at my
CORROSION TOPICS page. Lots
of
unfortunate mistakes and cures. Complete with close-ups!!!
The
EICO
710
GDO
was one of the more successful tube-type,
AC line powered, GDOs.
It had a frequency range of 400kHz-250MHz
in 8 overlapping ranges. Even though it was a kit, it-as with all other
KIT
GDOs I am aware
of-used pre-wound plug-in coils wound to a 0.5%
accuracy on polystyrene forms.
A GDO
is basically a wide-range oscillator with a meter in the grid-return
line to indicate when the resonant frequency (of the tuned circuit it is
loosely coupled
to) matches the frequency of the GDO
oscillator. That happens because the tuned circuit-under-test absorbs
the energy of the oscillator, causing the
"dip" of the meter needle downwards. If
that oscillator is reasonably calibrated, you then know the approximate
resonant frequency of your coil-capacitor combination.
The
EICO
710
GDO
uses a 1:7
planetary drive on the tuning capacitor. It uses a
6AF4A in a Colpitts
oscillator circuit. It is transformer-operated, and uses about
10W of power. The
rectifier is a selenium
, and I would strongly recommend:
1) measuring
the DC voltage at its output; 2)
and then exchanging it for a suitable silicon diode. You should then
3) insert an
appropriate dropping resistor to cut the voltage back down to its
original value.
Measurements for the
EICO
710
GDO
are: 2.25" high;
2.6" wide; &
6.9" long. It
weighs approximately 3 lbs.
The exterior is Steel and Grey wrinkle finish.
The
EICO 710-A
GDO is a private-labeled solid-state unit
identical to the Leader LDM-815 and the
Loadstar KDM-6. I had never seen or heard
of one 'til I found this one on ebay.
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