Hi Rainer,
Are you really married to the idea of measuring the current? I think
you could test the switch without too much difficulty if you've got the right
vintage console.
Can you acquire a 2H spectrum on that probe? (I normally read in the
gradshim1d2h parameter set, set TD and SI to reasonable values, and pulprog
to zg2h and then acquire normally.) This will also let you check the
tuning on the lock channel. And if the lock channel is just WAY out
of tune you'd see this symptom--it would require a lot more power than normal.
I think if the switch were bad I would expect the lock signal to behave normally
as far as the power required, but I would expect it to be EXTREMELY weak.
But if it's way out of tune then you could pulse the lock with a lot more power
and not saturate it.
Anyway, if you can acquire a 2H spectrum and then put the preamp into bypass
mode you can compare the two. If things are working properly you expect
the normal sensitivity to be 2x of that in bypass mode. If the switch is
busted then I would expect the sensitivity in normal mode to be really bad and
in bypass mode to be reasonable.
Anyway, if you can send which model spectrometer you have, I can provide better
instructions for putting it in bypass mode.
Cheers,Mike
On Thursday, October 3, 2024 at 06:08:23 AM MDT, Platz Hirsch wrote:
Hello again,
the story with an apparently broken deuterium preamplifier within a cryoprobe
continues.
What we have is a cryoprobe, which needs very high lock power to get a
reasonable lock signal. With a high probability the T/R switch of the built
in deuterium preamplifier is broken.
We made some measurements.
- Output signal of the deuterium transmitter of the console: o.K.
- Same signal at the output of the HPPR deuterium preamplifier: o.K.
- DC offset to trigger the internal T/R switch at the output of the HPPR
deuterium preamplifier: o.K.
According to the technical manual the current of this DC bias signal should
be 25 mA. Internally this signal is Labelled as CRP_TXSW.
For the moment I am looking for ideas, how to measure this current. Presumably
this wouldn’t help, but I would be Happy to know the reason of the lock
failure, before removing the probe and organizing the repair.
Greetings
Rainer
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Received on Thu Oct 03 2024 - 06:18:15 MST