Advantest R3131A Spectrum Analyzer 9KHz-3GHz

[flolic]

Just for the reference, I have tried motherboard reset button but it's the same as before. Never mind, it's not really a problem.
OTOH, SA does not pass self test every time when warm, it will fail in Total gain test. Calibration fail with IF step amp error. So, time to replace 4072 opamps and analog switches.

[rainbow]

Have a nice repair ;-)

[dtxy101]

  Hello, everyone, I am repairing my R3131A. My TG output frequency has shifted by 14MHZ. After removing the adjusting resistor of VCO (a 0 ohm 0805 patch resistor), the frequency output returns to normal, and the frequency output is normal from 10MHZ to 1.8GHZ. However, there are still faults: the output of TG signal is not linear, and there are several points where the output jumps, for example, 0 DBM-9.9 DBM is set, and the maximum output is -30DBM. When the knob is lowered, the output gradually decreases. Set-10 DBM-19.9 DBM, and the maximum output is -15DBM. When the knob is turned down, the output gradually decreases. Check that there are 3 ATT circuits on the PCB:-10 dB att; -20DBA ATT ; -20DBB ATT ; TG signal output attenuation switching failure?
Who has a picture of the PCB of TG output part, three resistors of 10DB ATT, two of which are 100 ohms, and how many ohms is the other one? I can't see this one clearly.

[dtxy101]

What is the resistance of the resistor in the red circle?

[nctnico]

It is a pi-pad attenuator so you can derive the value:
https://www.electronics-tutorials.ws/attenuators/pi-pad-attenuator.html

[Renaud F5ZR]

Hi,
I'm new here. I just bought a R3131 in need of work.
I downloaded two Operation Manuals
FOE-8311227H00 Dec. 1 1997
FOE-8311227D02 Dec. 1 1997
They are quite different. Any comment about them?

Also one Maintenance Manual:
FME-8335142B00
As I will print them (having them printed rather!) I'd prefer to choose the right one first. Of course I will need the serial # of mine when I receive it.
This was just to introduce me and my new toy.
I read all of this remarquable post from the beginning when I was looking for a R3131 but I probably should have opened a new one, sorry.
Renaud

[Renaud F5ZR]

I'll answer my own questions above myself.

Now that I have read the Advantest docs I understand why nobody took the trouble to do it.
Even if I read all this post from the beginning the newbie could not believe the Maintenance Manual was of no use at all.
Now I do!
Renaud F5ZoulouRadio

[ABC]

Hello everybody,
My R3131A has an error as shown in the figure. Where is the fault? Which board is broken, please advise!

[ARF]

I'll refresh the topic.
I recently received a R3131 and replaced the battery.

Like many others, self-testing falls on “Total Gain” and auto-calibration falls on “IF STEP AMP”.
I've seen a method of replacing the resistor and adding +2dB this way. But this is a hack..

Has anyone found the real cause of this problem?

[ARF]

Fixed.



The issue was in the 4th section of the IF/LOG board. I replaced the AD606 log opamp (a $40 part) and it was not failing as bad - there was a small amount more gain in the stepamp test stage.
I then replaced the AD826 opamps after that. No change. Then I replaced the two 4072 opamps at the very tail end of the IF board. These drive the signal through the backplane connector onto the ADC / CPU board where it is digitized. Replaced both here and the problem was fixed.
The original is an ON Semi 4072 family, my replacement was MC34072DR2G.

After running warm for an hour it still passes with flying colors.

Thanks to everyone for your support

I tried it. I replaced them with a TL082 - which has exactly the same internal design as the 4072. I got exactly the same thing. If I disable calibration, then my device has a lower level by 5 dBm, which is of course beyond the possibility of compensation. The problem is located before the IF unit, of course.