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Troubleshooting E4406A

Question asked by Ole on Oct 6, 2013
Hello, all

I have a E4406A that has developed a fault, and I can't really figure it out. Hoping that someone on the list 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. It also seemed like the lockups was temperature dependant; after a lockup, it would increase the chances of a successful reboot if I left the instrument off for an hour.

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 nott successfully booted it even once, so whatever has deteriorated, has deteriorated on standby-power..

In short, I'm stumped. Any hints?