Corby,
many thanks for the comprehensive instructions.
After the harmonic generator alignment I measured 90mV into the 10Meg
DMM input, so the beam current should be 9nA.
The floor with the harmonic generator pot fully ccw was 6nA.
I didn't change the generator output during the LF test. To get to the
maximum, I just had to increase the frequency up to about twice the
initial value of some 21kHz. The peak was a lot above the noise.
But, now I'm suspecting that the CBT has probably been exchanged by the
previous owner and not been set up correctly.
Either he decided to dispose a dead CBT or he gave up half way... I hope
the latter.
On the CBT label it says EM voltage -1615V. The applied voltage is
actually -2500V.
I see in an old post you mentioned that the higher voltage should be ok
for now.
Well, and something with the Zeeman frequency appears to be wrong, too.
The measured (some) 41,6kHz from the LF test don't match the 53.53kHz
sticker on the door. So I'm wondering what else needs to be checked.
The synthesizer output is 12.631,771,6MHz as indicated in the manual.
Btw. this 5061A has Opt. H96 which seems to indicate the added alarm and
continuous operation outputs on the rear, and a A5 time delay divider.
There is no clock.
Thanks,
Adrian
[email protected] schrieb:
Adrian,
Most used High stability tubes are DOA but you might get lucky!
You say the low frequency test "worked".
What was the amplitude of the peak in nanoamps and was the peak well
above the noise or baseline level?
Once you were on the peak did you adjust the 41.6Khz amplitude to max the
signal?
Once on the peak you can adjust the mass spec pot on the top of A11 to
peak it.
If the peak was >8na and above noise then the tube appears to be working.
Anything below 4 or 5 na the tube is depleted, might be useable but STS
will be terrible.
If the peak is >8na then reconfigure for normal operation, in open loop
mode.
Turn the mod on and connect a scope to A8 J1 to observe the phase
detector output.
Adjust the fine and or coarse oscillator adjustments back and forth
across 5Mhz.
If you can see any output as you sweep through then set the osc.
frequency to peak the signal.
Then adjust the A3 mod and the A4 (top pot) to peak the signal.
A7 gain will adjust the amplitude.
Adj the osc freq. to null the signal (puts you "on" frequency) and see if
you have any 2nd harmonic now.
If so go ahead and see if it will lock.
Good Luck!
Corby
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