7T11 diode tunnel destroyed connecting a 15pF 1:10 probe?


Miguel Work
 

Hi Tom

Yes, the output tunnel diode was "working", but it haves >100 ohms resistance

Arm diode is ok, but is diferent kind, is a 10pf, de output is a <5pff

When I first tested operation I don´t have output in trigger otuput, so I went directly to test TD operation with probe.

Output TD was bad, open, so I replaced it with the same diode. It worked but only for a few minutes, bias pot was at max, but I don´t belive that this was the cause of the problem,

Some times it has a 100 ohms resistor, others is open, the second diode that I replaced

Then I have replaced it for a russian AI201A 3.5pF 10mA GaAs and now is working

So, I suspect that the capacitance probe has some efect destroying the TD diode. Tunnel diode is connected to -15V, so when I connect the probe it charges 15pF, capacitance probe, through the tunnel diode.


Tom Lee
 

Hi Miguel,

Although anything is possible, killing a tunnel diode with ESD from a scope probe is pretty improbable. Over most of its I-V characteristic, a tunnel diode looks like a very low resistance, which is extremely effective at snubbing.

Also, I haven't followed this thread too closely, so I don't know what testing led you to conclude that the TD is dead. If you used a multimeter, a good TD will be hard to differentiate from a shorted TD. You can reliably identify an open TD with a multimeter, but you need to use other means to test a TD reliably in the general case.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 9/13/2021 01:35, Miguel Work wrote:
gnd scope is connected to ground, which is the maximun energy that the diode can withstand?




Miguel Work
 

gnd scope is connected to ground, which is the maximun energy that the diode can withstand?


guy_ellis_1964
 

ESD?


Miguel Work
 

Can a 15pf probe destroy the CR152? 1:10 ground clip is connected to chassis. Diode is connected to -15V.