Hi,

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Looking at this trace on the graph, what catches my attention is the fact that the control voltage applied to the YTO makes jumps at the start and end of the YTO range, and is linear in places, but mostly the fact that part is curved.

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Maybe the YTO driver is more complex than I imagine. Perhaps there is switching in the transconductance amp powering the YIG coils, and one or more of these circuit sections are distorting...hard to say.

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I saw a friend of mine yesterday, and he had three 8133As available to do some quick testing. On 2 of these generators tested, there was a relay problem, one was on the CH2, normal output, and the other was on the reversed output. Their problems were exactly the same as on my 8133A which I ended up repairing. No doubt this problem is recurring on these generators.

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I measured the FM modulation at Spectrum at 500 MHz on these two generators, and I had the same result as on mine...this would seem normal behavior.

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I had the opportunity to use a CS803C and SD-22, and it was possible to watch the signal in PRBS mode. However, in the trigger menu it was necessary to use the EXTERNAL DIRECT trig, to switch from VARIABLE PERSISTENCE mode.

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For the CH2 relay, if the repair fails, this part is available on eBay.

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Thanks Yves,

Collecting data for frequency accuracy analysis is lengthy task. I wrote a powershell script to set frequency, read 8133A internal frequency counter reading (and the external frequency counter connected to the ch1 output.
I stepped frequency 1Mhz from 34Mhz to 3.5Ghz. The plot below shows the frequency error (set-reading from 8133A internal counter). Indeed there is some frequency issue in some bands, which does not have explanation.


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Regarding ch2 relay issue, I plan to open my unit tomorrow and try to fixt it. Let's see how it goes. Thanks for your step by step instruciton.

Thanks!