RubenRubio -
First read through the section of the manual describing the internal diagnostics available - good idea to NOT mess with the calibration constants until you have identified a problem. You can restore the constants to their original value - see the instruction manual.
Try the following diagnostics:
PRESET[Green key], SHIFT[blue key]' M4 - General diagnostic that tries to check some DACS and other functions
Then
PRESET,SHIFT,METER[ on the lower skirt of the front panel]' rotate the RPG [knob on the front panel] and observe if the power output varies smoothly from max to min
If this works
Test the attenuator by PRESET,CW,RPG [rotate the RPG and see if the power level decreases linearly] - it there is an attenuator problem, you will find points where the power jumps up (typically around the 10 dB points - ~13, -23, etc)
Also, before doing anything check the power supply voltages and ripple
Have fun
Cheers!
bruce
Quoting RubenRubio <rubenrb2019@...>:
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Hello there!
Recently I bought a 8341A opt 001 and 002 synthesized sweep with a problem of 'shut down after a while' but the reality is the unit doesn't shut down at all, but leveling problems. And hard ones ...
Yesterday I was using my variac with 120 vac (the unit came from the States and I am in Spain). It worked for about four hours and don't make any noise, smell or weird thing related to the power supply, so I don't know why the seller said that.
The +20 volt rail is spot on since the variac reaches 90 vac, and the other rails are reasonably on specs. Fan runs ok, I was thinking my 8663A are loud... this sweeper sounds like a subway train :D (maybe because of running without all panels for inspection).
My first impressions in CW mode :
- *frequency* chopping is pretty accurate all over the four bands, checked with my 5342A, sharing the counter's 10 MHz reference.
- *leveling* is an absolute disaster all over the four bands, but looking more stable requiring 0 dBm in the 2.3-7.0 GHz zone (that's band 1 according to the manual). The behavior of the entry display vs the power display is very tricky to explain :D My unit is equiped with -90 dBm attenuator at the output, but I think it works properly¡ some loop jumps randomly taking down the level a few dBm while the frequency varies. The measured level and level shown in the 'power dBm' always matches (measured with a 8481A w 436A). But when you enter a dBm value on entry displays, the actual level fly free. Sometimes I can 'catch' the real level using the knob to equal numbers of both displays and then I can take down the real level a few dBm and the again loose control.
For the moment, I cannot see the spectral purity without a broadband spectrum analyzer (only imagine the jumping signal :D) and the AM modulation because I don't have enough equipment for the moment (broadband mixer and LO)
I already tried to re-enter de calibration constants printed in an ancient papyrum placed inside the unit. I only need to modify the values of six constants:?9, 10 and 11 (YTM gain) and 50, 51 and 52 (YTM BX gain), the other constants matches with the paper. And then, after an 'Automatic Tracking Calibration', those values change again :( Saved the modifications and still UNLEVELED light on... I tried without the recommended tracking calibration and the same outcome.
Any guy or gal that have same issues or some advice on this topic?
Best regards,
R.
