Troubleshooting an Agilent E4406A - Page 1
Forum section: electronics / testgear

author: olepr01@gmail.com
author_rank: Contributor
timestamp: October 06, 2013, 11:09:03 am
content: Hello, allI have a E4406A that has developed a fault, and I can't really figure it out. Hoping that someone on the forum has seen a similar failuremode, or has some good tips..The E4406A in question was working perfectly, and then suddenly froze up. Rebooting worked, and it worked fine again for a few hours. Then locked up again. Nothing in the logs. As time went on, the intervals between lockups became shorter and shorter, and now it does not boot up at all, or sometimes boots "half way", freezing in the middle of the boot process.My first thought was that it was the flash that was bad, but as it can freeze in the middle of printing a line of text, I doubt it. The LED's on the CPU-board sometimes stay lit, and nothing happens. Sometimes they blink a little, and stop with two or three leds still on. The manual states that all leds should be off when the cpu is properly booted. The codes displayed by the four leds is not described in the manual, anyone know?I've checked the +-12V rails, and they are fine. I see a 30Mhz squarewave with the correct levels on TP104 on the A10 digital IF board. The manual states that the pci-bus will freeze if the sampleclock is not present, and based on the symptoms that is my "favourite theory". However, as I see the signal, I do not know what else may be wrong.The rest of the troubleshooting described in the manual requires various riserboards, which I do not have, and the layout of the analyzer makes it very hard to access mostly everything..One last piece of information, when I opened it up, it was pretty much PACKED with dust.. So it is not at all impossible that something has overheated, and progressively deteriorated..That said, it did boot up perhaps 20% of the time untill I powered it down and left it for a few weeks (gathering the fortitude to start troubleshooting). After this I have not successfully booted it even once, so whatever has deteriorated, has deteriorated on standby-power..In short, I'm stumped. Any hints?

author: free_electron
author_rank: Super Contributor
timestamp: October 06, 2013, 11:57:00 am
content: This smells like capascitors drying out....Check the ripple on those rails.. Take a long hard look at the main power supply brick.. I'd change the output capacitors to negin with.

author: olepr01@gmail.com
author_rank: Contributor
timestamp: October 06, 2013, 01:57:33 pm
content: THanks, didn't think to check the ripple.There's several rails in the instrument, but most are accessible only with a special riserboard; guess I need to get more invasive with the powerbrick. Unfortunately it can not be accessed while plugged in, so I guess I solder some sensewires and try to get at them that way.. Thanks!

author: andy_silicon
author_rank: Regular Contributor
timestamp: October 06, 2013, 02:54:48 pm
content: The last time this happened to me (E4406A owner) I removed and cleaned every board - paying careful attention to cleaning the board connectors and sockets with canned air , a toothbrush and iso-propanol.No boot problems have since re-occured.( for me the boot would randomly fail - or the installed hardware would be wrongly detected , also I'd suffer from reboots and hanging ).I hope your problem is as simple as that.

author: olepr01@gmail.com
author_rank: Contributor
timestamp: October 07, 2013, 08:20:46 am
content: It really does sound like a similar situation.. I have cleaned out the connectors and reseated the boards several times, but I have not really cleaned the boards themselves apart from compressed air. Time to get a bit more thorough, I suppose. I also notice that every now and then when I try to boot it, the RPM of the fans drops ever so slightly for a few seconds, and I can se the 14.8v rail on the probe powersupply on the front panel drops a volt or so.. Do you see/hear anything like that on a "successful boot"? It does not happen every time, and I have not been able to correlate that with a "partial boot" (i.e. the CPU leds blinks for a few seconds before freezing, as opposed to staying lit and doing nothing)

author: andy_silicon
author_rank: Regular Contributor
timestamp: October 07, 2013, 02:48:59 pm
content: When I'm back at the machine I'll power it up and check.

author: andy_silicon
author_rank: Regular Contributor
timestamp: October 07, 2013, 05:12:30 pm
content: Okay - I powered the machine.Immediately after pressing the power button the fan runs lets say at 105%Before the LCD shows any text the fan reduces to the normal running speed ( maybe 3 or 4 seconds to reach that point ) 100%.There is then no change to running speed of the fans.Any more questions just ask.

author: BMac
author_rank: Contributor
timestamp: November 05, 2013, 03:08:38 pm
content: Any luck on your E4406A? I have one that wont run the bootloader as well!Thanks,BMac

author: kjk24
author_rank: Regular Contributor
timestamp: October 31, 2017, 09:30:46 am
content: still not working ? i have a working unit, i can measure or copy staff for you.let me know