Agilent HP E4406A VSA failed selftest, no signal... BOARD REPLACED

[Ordinaryman1971]

Hi everyone,
I've got myself a failed E4406A Vector Signal Analyzer.
It fails self test: IF Gain Curve, Nominal System Gain and 321MHz Amplitude
When attempted to feed it with practically any frequency, only at about 20dB I can see some small signal poking through the signal floor (with 7db attenuator removed)....
I believe somebody injected a lot of power into the input, the VSA is limited to 35dB.
I've tested the 7db attenuator that's at the input and it tested 32dB... I've removed it all together, to be replaced (I promise to be very careful).
I've swapped the RF board with my other E4406A and it tested all good so the RF board is definitely a culprit.
So, any ideas how to approach it, or maybe somebody out there has a board I can buy.
And no, I don't want to buy board from eBay, they are way overpriced and I can buy the whole 4406 for a price of one of those.

[Tony_G]

I have something similar happening on one of my E4406A's and I traced it to the relay right after where 7dB attenuator output connects on the board. Of course the IC is unobtanium and seems to use an undocumented aspect of the original part (driving +/- 9V rather -9 to 0V). So far I haven't been successful in finding a drop in replacement.

You might want to take a look there and see if it is the same issue.

TonyG

[Ordinaryman1971]

I've watched your videos and was almost sure that's the same problem but when I wend "medieval" on my switch bridging the contacts the same way you did... I just got more failures.
But I've done it with switch in place... so maybe I should remove it from the board and try one more time.... exactly the way you did.... advice?
Whatever was the power that was applied to the input it was enough to change the attenuation of the 7db pad to 32db... that was measured at 50MHz.
I've tested the same attenuation at higher frequencies and it's less but still out of spec.

[Tony_G]

i'd try with it removed but there is an amplifier section right behind that switch (which, as an aside, I think is being hurt by the DC offset introduced by the switch in my case). If they fried the attenuator and the switch then they might have hosed that as well.

TonyG

[Ordinaryman1971]

I've found a replacement board. All working now.

[RCHRDM]

Hello

I have an E4406A and recently installed a used flash memory board.  I used an Agilent maintenance disk to make a backup floppy from the old flash memory board.  The old flash memory board worked OK, but had limited memory.

Now, with the new board, I am getting an error at startup that the E4406A cannot find "Synthesizer Cal Coefficients."  I thought this would be on the backup floppy, which I installed after I put in the new flash memory board.

Can anyone help me fix this error?

Richard