I dont quite see how you managed to exceed Ip with 1k and 2.5V. Could you explain what drive you adjusted?
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Until you exceed Ip, the TD is going to look like a low-ohm resistor.
--- In TekScopes@yahoogroups.com, "cybertheque_museum" <msg.together@...> wrote:
It is difficult to accept that all four tunnel diodes in my recently acquired 475 scope are shorted but that is what the I am seeing with a kludged curve tracer and DMM resistance check. How likely is it that all four are bad? The curve tracer is just a 1kohm resistor from ground to the cathode of the TD under test with the anode driven directly from a -2.5 to +2.5 V triangle wave generator (about 600 ohm output Z) to ground and the X axis of the monitor scope connected between ground and the function generator and the y axis between ground and the high side of the resistor (the monitor scope is not ground isolated so I cannot look directly across the TD junction).
Substituting a convention PN diode and also a Schottky diode for the TD shows the usual knee on the monitor scope. The data for the 1N3718 are:
IsubP = 10 ma
IsubV = 1.3 ma
VsubP = 65 mv
VsubV = 350 mv
I adjusted the drive to cover these ranges. The displayed curve is just a diagonal line with a slope of 1.