Hi all,
?
I have a problem with my E4437B that started gradually as jitter, but now just outputs white noise.? I used to repair ESG RF boards, and know the generators relatively well, but haven't seen this issue before.
I had been measuring internal stability by using my 53132A?(500KHz for best ?Hz resolution), set with an offset, and recording the resulting offset, recording a range of 1 - 15 ?Hz. Just recently, it started getting worse, and worse, and at times jumping to outrageous frequency errors.? ?However, there were no indicated errors until today.
?
?
The bandpass filters are switching properly, but show white noise covering the entire bandwidth of the filters, and the white noise levels change drastically with frequency, and am now seeing an "UNLEVEL" indication, which is likely due to to the signal generation failure.? One note, when I select 400MHz, I get a secondary output at 800MHz (-55dBm with output set at 0dBm), which attenuates severely with only a few hundred KHz change.? The high level of the 800MHz is likely due to the output board trying to ink out as much level as possible, but is not able to.
?
My first dread was that it might be the YIG, as they are such a pain, and very expensive (I don't have any experience with them, just the RF boards in the cage).? I have also been considering the U313 (1GC1-4210) Frac-N divider on the E4423-60019 SYNTH BD, which I know is a weak spot.? I haven't opened it up yet, but plan to in the next few days.? Since the YIG drives the FRAC-N board directly, I will check for a clean signal there, then at the output of the FRAC-N divider.? Fortunately, I have an E4404B spectrum analyzer, so I can look directly at the YIG output.
Fortunately, I have a couple new, but slightly damaged (scratched on top of the chip, which obliterated the part number) 1GC1-4210 replacements, as I used to repair these boards, and the regular rework person messed up a few chips with tweezers.
Thanks in advance for the help.
Tom -- KJ6SVS --
