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Advantest R3767 / R3765 VNA Service Manual

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kjk24:
still not solved,

only some infos to share with you.

at my device
 -YTO is stable at 4.4GHz and has around -2dBm output,
   i dont understand here the maintenance manual, the setting for the YTO is not clear for me. 4.4GHz or 4.44Ghz ?
 - @Hold, span0 the syntesizer is locked and on all frequency up to 8GHz stable.
if the span is small (200MHz) and sweep is slow @10Hz it is still locked.
but when the span is larger the frq jumps somtimes for and backward, if the span is large and sweep i faster it get out of lock and sythesizer is unlocked.
then i have to reboot and bring it emidently to 0 span and 10MHz otherwise its Syth. unlock again.

the synth. who mix the first Lo get the jumping values digital i into the two dac.

best wiches
kai

Gyorgy Albert:
Hello All,

I recently activated my R3767CG, which was sitting on the shelf for more than 10 years. Of course, the 3.6V RAM battery was empty. I replaced it, but I am still getting the RAM error at the start-up test. I know that for several Advantest analyzers the RAM reset procedure is known (I also used similar procedures for the other Advantest analyzers), I tried all documented key combinations (found in the documents of the Advantest instruments IO group), but none works for my R3767.

Is there anybody who can help me with the procedure for the R3767? I asked the company from where it was purchased (about 20 years ago) if they can help me, on return they sent me an offer for  repair (I have to sit down when I saw the figure). We paid at that time a little fortune to them, and I expected to get some help. But it seems that it is not possible

Thanks in advance,
Gyorgy

esoteq:
Hi Kai,
still reading this sometimes
I had the same problem. When trying to fix it YIG failed finally.
I scrapped it and used the front panel to a faulty R3565, which now works great. 
But I had suspicious finding. The level from the comb generator to the ch samplers is low.
I think it should be at least  > 5dBm but was c. -5dBm. Check that ...your opinion ?
And (hence) the level of it from the R-(sub)sampler to the PLL creating 840kHz IF was very very low. PLL might have hard time to lock on it ?
In my case it locked sometimes temporarily to a wrong harmonic.
Some of the elco's had also high ERS. Bought new elco's, but the YIG failed before getting them.
I have all the remaining part for free it needed.
The input directional couplers are very good for feeding bias in testing active devices.

Erkka
OH1NS

kjk24:
Hi,
My unit is still on the bench, i can measure it for you to compare it.

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