Re: E4401B No 50MHZ Cal signal
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Hello Mike,
I would first check out that Local Oscillator, I suspect your's is not there.? If I recall the cal signal is derived from the root source (YIG LO) which is fed as a reference into the 1st converter? via direct or through a LO Distribution amp.? This LO rhythm needs to be around +12 to +15 dbm in level.? Best of luck!
Jon?
On Saturday, March 30, 2019, 12:06:13 PM CDT, Michael Williams <mike@...> wrote:
Hi Peter,
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I am aware of the differences between a 75 ohm input and 50 ohm input.? I have a 50 to 75 ohm impedance matching pad that I will be using on the input when measuring signals with a 50 ohm source.? I know this is not ideal, but will work
for the things I plan to do with this gear.
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The issue I am having at this time is that the *internal* 50 mhz calibration signal is not getting generated, causing issues during the alignment procedure.? Unfortunately, on this model, the input is switched internally to the calibration
signal, so I can¡¯t even use an external signal to get through the alignment.
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Thanks,
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Mike
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Are you using 75 ohm components to calibrate it?
You do realize that it will not work with 50 ohm components?
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On Sat, Mar 30, 2019 at 12:50 PM Michael Williams < mike@...> wrote:
Greetings,
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I have an Agilent E4401B with option 1DP (75 ohm input) and option A4H (GPIB interface) that I recently found at a swap meet.
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It powers up, displays a trace, and when I apply a test signal to the input, I can see it on the display ¨C so far so good.? The only downside at this point is a persistent message
that an alignment is necessary.
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The problem is that the alignment procedure fails.? After running an ¡°align now¡± the noise floor is off the top of the screen.? I have also noticed that when selecting the internal
50 MHZ source, I do not see a corresponding signal on the screen.? This leads me to believe that the internal 50 mhz signal is not getting generated, causing the alignment procedure to turn the internal gain up way too high.?
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I have the component level schematics for the device, and have confirmed that on the RF assembly, the 2nd VCO is not receiving power because the ¡°TEST MUX¡± ¨C U56 is not
getting enabled ¨C All of the MUX lines (MUX_EN, MUX_0-MUX_2) are all at 0 v.?
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This is where I¡¯m stuck ¨C I see that U55 (Fractional Divider) has connections the MUX pins, but have no idea what tells it to place the MUX into a given state.? I can¡¯t tell if
this is a logic/software issue, cabling, or a bad U55.
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I¡¯m hoping that someone here with more familiarity with these instruments has some insight as to what might be causing this, and next steps I should take to figure out the issue.
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Thanks!
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Mike Williams
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