I have seen several 8563E, 8561E spectrum analyzers with about 500KHz spurious at a level of -50dbc.
I believe the spurious is generated at the Fractional N Synthesizer at the A14 Frequency Control Assembly.
Has someone noticed this and found a cure for it?
Is there a simple way to reduce this spurious level? Replace the The Fractional N divider?
I have the schematics for this Assembly and I am willing to share it with someone that can help.
Problem traced to a faliure in the power supply regulator assembly p/n 08564-60009.
I have replaced the regulator assembly and the spurious disappeared .
I will troubleshoot the regulator assembly and will advise about the required repair.
I'm trying to repair an 8563E spectrum analyzer for personal use and I'm also seeing the exact same spurious signal at 480-500kHz offset (about -57dBc) on the 300MHz CAL OUTPUT. I get similar levels looking at an external signal generator.
I'm guessing its the 6th harmonic of the ~80kHz switch-mode supply getting on to the 100MHz/300MHz/600MHz board and modulating the outputs?
So, is the fault generally caused by failing 2700uF, 6800uF and 220uF smoothing capacitors or do also need to replace the dual diode rectifiers (e.g. VHE2402A) as per Section E "OUTPUT RECTIFIER" of the schematic (See attached)?
So I've replaced the capacitors and now I appear to have a different PSU issue.
Does anyone have a schematic or CLIP for the A6A2 module? (08564-60009)
With only a few of the main PCB's plugged on to the J1 ribbon the unit starts up, but as I plug-in more boards the +5V rail and the +15V rail start to drop (settling at about 2.8V and 8V respectively. The PSU is also "squealing" a little and the N-ch IRFZ40 FETs & 220uF output capacitors are getting rather toasty (probably due to the ripple current as the FETs turn on and off). The unregulated voltages heading in to the A6A2 module appear to be the expected average levels (+6.8V and +17V), but they droop when then N-ch FETs turn on.
Either another fault has developed on one of the main PCBs attached to J1 ribbon or the PSUs ability to deliver current has diminished.
Does anyone have any suggestions or insight before I start ordering replacement ICs for the A6A2 board and output regulator FETs?