Advantest U3751 (SA) "RF Unlocked" / PLL issue?

[dgiese]

Hi,
I got a Advantest U3751 in my hands. It was about to be thrown away as it has this weird error. It was manufactured in 2005, so its a while. Advantest is not really helpful in regard to service manuals.
After booting up, the device shows "Warning 7/81 RF Unlocked". When I run the Self-test, it complains about the RF_Registers and RF_PLL_Lock. The LO_PLL_Lock seems to be fine.

I tried to hook up an external reference with 10MHz, but that did not make the warning disappear. I am kinda unsure where to look. The U3700 series does not seem to be too common.
In the background of the warning the device seems to do its measurements. The test signals (e.g. 900MHz, 3GHz) I put on the input were off by a couple dozens kHz.

Anyone had the same issue or an idea? Its a nice Signal Analyzer and I really want to use it

[Gyorgy Albert]

Hello,

I have a Advantest U3751, and I am looking to get in contact with other people who is owning/using this SA. I have some minor problems (some major were solved), but it seems that there are not too many users of this analyzer. I would appreciate is someone is reading this post, could reply, or send a message to me. As everybody knows, Advantest is not very friendly in such matters, and they are not giving any kind of service/maintenance information.

Thanks,
Gyorgy

 

[dgiese]

My device is still un-assembled on my desk. I did a teardown, you can find them here: https://dontvacuum.me/teardowns/advantest-u3751

I did also dump the CF card. I noticed, that the device actually works, but that there is an permanent offset. I was actually thinking of patching the error message, but got other stuff to do.
Its kinda sad as that device is in a very convinient package.

I have a few friends that work at Rohde&Schwarz, which apparently marketed the device a while ago. But they don't have access to any material