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A look inside of an Agilent E4400B signal generator

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feedback.loop:
Check it out. Another lucky find from eBay. This Agilent E4400B generator has some problem with fractional PLL. It seems to be unstable, so the instrument periodically shows error 508 "Frac-N Loop Unlocked". The synthesizer was inspected, the block diagram was discussed and the blocks were located on the board. Unfortunately, there was no definite solution to the problem due to lack of appropriate equipment at the moment. If there will be any developments, another video might follow.

Calibration guide: http://literature.cdn.keysight.com/litweb/pdf/E4400-90325.pdf

Document with the block diagram. It is for a different model, which seems to use the same synthesizer:
http://cp.literature.agilent.com/litweb/pdf/E4400-90014.pdf

https://youtu.be/JPEmbvUx0JQ

TheSteve:
I have not watched the video at all, just wondering if any Avago MMIC parts are part of the chain in the problem area - perhaps marked A06 or A07.

feedback.loop:

--- Quote from: TheSteve on February 22, 2016, 03:19:14 am ---I have not watched the video at all, just wondering if any Avago MMIC parts are part of the chain in the problem area - perhaps marked A06 or A07.

--- End quote ---

There are a few micro-x packages marked A0x. U15 marked A07 and U16 marked A06 seem to be a part of the buffer, which might be in the PLL loop. There are a few A03 ones in the buffer and divide by 2 section, and one more in the VCO. What about them? Why did you bring them up? Are they known for failing? Can you identify them in the photo? Do you happen to have data sheets?
Thanks.

TheSteve:
I have no experience with the unit you have, but have seen the Avago parts fail before in similar devices. I have seen them still pass/amplify a signal but it will be noisy which can make it hard to diagnose.
The full part numbers of the various parts are A07=MSA-0786, A06=MSA-0686 etc.

feedback.loop:

--- Quote from: TheSteve on February 22, 2016, 05:52:58 am ---I have no experience with the unit you have, but have seen the Avago parts fail before in similar devices. I have seen them still pass/amplify a signal but it will be noisy which can make it hard to diagnose.
The full part numbers of the various parts are A07=MSA-0786, A06=MSA-0686 etc.

--- End quote ---

I am looking at the data sheets. The package is sot86, not micro-x. MSA-0786 is rated up to 0.8GHz. So if you are right that A07 in this generator is MSA-0786, I wonder why it is used up to 1GHz. I hope they are not at fault since they are not available neither on Digikey nor on Mouser.

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