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E5052A Power On Test (3.3V Bus Supply)
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Great!? That's the best kind of repair; when you learn something in addition to getting it working again. Jim Ford Laguna Hills, California, USA
On Saturday, March 1, 2025 at 05:43:25 AM CST, jmr via groups.io <jmrhzu@...> wrote:
It's all OK now, I took it apart and fixed it :) :) :)
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On the DSP/ADC module A3 the 5V rail is now 4.97V (was 4.70V typical) and the 3V3 rail is now 3.24V (was 2.97V and very drifty).
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I disassembled the main firmware and worked out how it does the power on testing of the power supplies and this gave me the pass/fail limits for all the supplies.?
I was able to trace through the power supply distribution and see where it was losing voltage in a poor connection. A thermal camera helped a lot here. It's now all fixed and fine again!
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I also found out a few things about how it manages the internal 10 MHz reference and how to adjust the high stability 10 MHz OCXO. So that is now calibrated.
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I am so pleased, I thought it was slowly dying on me. There's no way I could afford to send it to Keysight for repair.
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I should be able to fix the other E5052A as well as it has a similar issue with a sagging 5V and a sagging 3V3 supply.
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It's all OK now, I took it apart and fixed it :) :) :)
?
On the DSP/ADC module A3 the 5V rail is now 4.97V (was 4.70V typical) and the 3V3 rail is now 3.24V (was 2.97V and very drifty).
?
I disassembled the main firmware and worked out how it does the power on testing of the power supplies and this gave me the pass/fail limits for all the supplies.?
I was able to trace through the power supply distribution and see where it was losing voltage in a poor connection. A thermal camera helped a lot here. It's now all fixed and fine again!
?
I also found out a few things about how it manages the internal 10 MHz reference and how to adjust the high stability 10 MHz OCXO. So that is now calibrated.
?
I am so pleased, I thought it was slowly dying on me. There's no way I could afford to send it to Keysight for repair.
?
I should be able to fix the other E5052A as well as it has a similar issue with a sagging 5V and a sagging 3V3 supply.
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These SSAs are fairly rare items as they weren't produced in high qty by Agilent and they were quite expensive when new. I think they were $80k to $90k new. So you might not find one even in a large and well equipped lab.
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I'm probably going to take the ATX power supply apart and check the electrolytic caps in it. There may also be some tired connections inside. The average power consumption is about 220W which probably puts quite a strain on the ATX PSU over a two decade timespan.
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开云体育Sounds about right. ?60 kHz is right in the range of a switching regulator of that era.I didn’t find a signal source analyzer around the particular lab I frequent, but I’d be very surprised if there weren’t one somewhere in this building. ?Literally tons of vintage test equipment lying around here, much of it from the old Hughes Aircraft days. ?Glad you at least figured out where the spur was coming from. Jim On Feb 24, 2025, at 12:53?PM, jmr via groups.io <jmrhzu@...> wrote:
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Turning the backlight off makes the spurious term go away when probing :)
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There is a soft menu button that turns off the backlight and pressing this makes the spurious vanish on the probe (that feeds to another spectrum analyser).
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Also if I do a screen grab via Excel and GPIB (with the backlight ON) the 60kHz spurious is present on the spectrum from the baseband input. But if I grab the screen with the backlight off the baseband spectrum is clean on the grabbed screen image in Excel. A huge improvement.
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I guess I can live with this when grabbing screen plots as (hopefully) I can add the 'backlight off' command to the excel routine.
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So screen grabs will look much better. I'll have a look for the backlight command in the programming guide... |
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Hi Jim, thanks.
I've just spent some time fishing around the outside of the chassis with a loop probe and the 60 kHz spurious is from the front of the instrument around the display. It isn't a single tone, it is spread over many kHz on the high side of 60 kHz and looks to be caused by digital traffic. It might be the display causing it. It seems to be at 59 kHz and it may be backlight related but it looks like it has some digital traffic on it.?
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Probing around the screen area of an E5071B VNA (I think this has the same touch screen display) shows exactly the same waveform so it is definitely screen related in some way. I'm not sure how this is getting into the baseband path but because it is also there on the main phase noise display I think it is getting in at the ADC/DSP module, possibly via a power supply rail. Hopefully a tired decoupling cap is the cause. |
开云体育Hi, Jeremy. ?Let me take a look around the labs here at Raytheon. ?Might be an E5052A or two that I could fire up. ?Give me a couple hours.Jim Ford? Laguna Hills, California, USA On Feb 24, 2025, at 10:17?AM, jmr via groups.io <jmrhzu@...> wrote:
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I wonder if anyone here has experience or access to an Agilent E5052A signal source analyser? Mine is about 20 years old and is recently showing signs of unreliability.
The main symptom is an occasional power on self test fail and it then reports issues with a 3V3 power supply voltage on the A3 DSP/ADC board where it reads low at typically 2.96V. I think a pass requires >2.96V but this may be firmware dependent. My E5052A is running the latest firmware V2.51.
I think this 3V3 supply is common across the backplane but it gets reported as an A3 test in the service menu. The 5V PSU rail also reads low at between 4.7 and 4.8V but this is still a pass (shows true for the test result) Also, for several years now it has shown a stubborn internal spurious at 60 kHz at a very low level. This very slightly spoils any phase noise measurements even though it shows up at about -140dBc then the trace is in phase noise mode in dBc/Hz. I'm not sure what causes this internal 60 kHz term, it may be from a PSU or the display or a divided clock. It may be that the 60kHz spurious term is a feature of this analyser as it is present on all my plots dating back over 13 years. It's not caused by anything nearby to the instrument as it does it regardless of position or proximity to other equipment. Plus the other E5052A I've used in the past (in a different location) is exactly the same.
The 60kHz spurious is also present when I swap across to the baseband input even with a very clean LF signal fed to the 0-40 MHz baseband input. So this spurious must be getting in at the ADC if it affects the baseband input as well. ?
I've seen similar on another E5052A that also shows a lowish 3V3 voltage (but it never shows a power on test failure) and it also has the permanent 60 kHz spurious on all phase noise tests on the main RF input.
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The service menu password is only three characters long and is 'kid'
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If anyone has access to a healthy E5052A could they enter the service menu and do a manual Power On Test (POT) in the service menus? Then report the 5V and 3.3V results for the A3 module
Mine shows anything from 2.91V to 3.05V and I think the pass/fail threshold for the POT is somewhere around 2.96V. The other E5052A I have some access to shows 2.982V to 3.08V and never reports a POT failure.
Thanks in advance for any replies
Jeremy
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