Advantest R3131A Spectrum Analyzer 9KHz-3GHz

[utkuzu]

I no longer have my R3131 but after I changed the battery on mine all I had to do was a self calibration and everything was fine. There is also a button near the rear on the motherboard which seems to load some defaults. I needed to press that one during startup to get my R3131 running properly after the battery swap.

I changed RF Tunes on engineer mode because tracking generator is not working right. After that I couldn't do calibration at all.

[nctnico]

Try pressing the button on the CPU board first. I'm not sure what it does or when you need to press it. I pressed it during startup and I kept it pressed for several seconds while the R3131 is running. Be creative here because all I know is that it fixed my problems.

[SaucySoliton]

I lost my factory default. Could you write me some values? Shift+5 , pass: 882323 , I RF, YTO Tune, Max1stLO and Min1stLO  hexadecimal values. Thanks your helps.

Max1stLO 0x0DA6
Min1stLO  0x0120

[SaabFAN]

I'm now too an owner of this type of Spectrum analyzer and naturally it didn't came home to me the way it was described on ebay: "Fully Functional".

The RTC-Battery is completely flat (I'm getting 0.002V out of circuit) and the Analyzer starts with a "RTC No Data" error. Everything else works fine.
Until I run the Self Test or the Calibration.

Calibration throws a "Error 100 IF Step Amp"-Message. And the Self Test claims the CPU is faulty. Which I cannot believe, as everything else is working although with a slightly lower measured amplitude than expected (about -2dB).

I'm off to get a new Battery now, but in the meantime I would like to ask what else could be wrong with the CPU-Board?

[SaabFAN]

As I suspected, the new battery solved the problem that the Self Test detected a faulty CPU.
For a short period of time, Error 100 "IF STEP AMP: Calibration Failure" was also gone. It took about 20 minutes of warmup for this error to reappear again.

What I noticed when checking the calibration feature, the -10dBm Cal-Signal is measured as 5dB too low with the Cal Correction turned Off. There also is at least some action happening when the IF Step Amp is being calibrated. So I guess that there's something wrong with the adjustments on the IF/LOG-Board.
Also when cold, and IF Step Amp is successful, the Cal-Signal is displayed as 1dB too high. Once the device is warmed up, it is about 0.3dB too high (at the edge of the specified uncertainty).

I hope that my device has "just" drifted too much and just requires some fiddling with the Pots. Do you know which Pots to turn, or is there any schematic, reverse engineered or from Advantest, that could give a hint on where to put the screwdriver? There is a video linked on page 2 of this thread that deals with this topic, but it is in french and I don't know french.

[nctnico]

This seems very similar to your problem and the solution appears to be replacing 2 DACs:
https://groups.yahoo.com/neo/groups/advantestinstrument/conversations/topics/139

Also discussed on the first page of this thread: https://www.eevblog.com/forum/testgear/advantest-r3131a-spectrum-analyzer-9khz-3ghz/msg245395/#msg245395

[SaabFAN]

Thx for the links. I have downloaded the zip-archive provided in the Yahoo Group and had a quick look through the folders.

Pretty interesting construction with varactors instead of trim-capacitors. I was thinking about using a similar construction in my own design, but opted for trim-caps in the end.


Btw. It currently appears as if my device is working now. Maybe it needed to cook out some moisture or just needed a few bangs after being ferried from estonia to germany via Air mail.
Also for a time it didn't want to update the date and time. Now it does...
Is there a newer Firmware available? The Revision Info says I have Revision C00 with no Options activated (there are none installed according to the sticker on the back).

[SaabFAN]

Okay, I have been playing around with the Analyzer and found something odd or rather worrying:
At +/- ca. 7MHz from the 30MHz Cal-Signal I see signals with a power of about -50dB. I haven't noticed those before and when I look at the manual, they are there but about 20dB lower.
I've also seen similar signals when I connect my PM5190.

My guess is that one of the Mixers is being overdriven, or has problems once fully warmed up. Power Measurements are still accurate though: The Signal from the PM5190 is pretty much the same that the scopes show and the Cal-Signal is sitting at -10dBm (ca. -12.5dBm with the Cal Correction turned off).


Btw. if anyone is still searching for a way to enable "forgotten" Options: When playing around with the instrument, I found out that SHIFT + 9 opens the Options-Menu, which is password protected (882323 worked for me). Once in there, the Tracking Generator and the "Type A"-Option (whatever that is) can be activated by the push of a button.
What does "Type A" in this context mean though? R3131"A", or is it the model with the second RF-Input?

[diarcy]

For those that have lost their "Options" on the R3131, I found a procedure on another Advantest Group that has restored my Tracking Generator.

Apparently, the procedure is also good for other options that may have been lost.

Here's the recovery procedure after losing your options due to a battery change:

Use the following sequence to restore the TG option:
<Shift> <9>
Password: 882323 <Hz>
"TG Option >"
"Load"
“Exit”

You should then be able to again use the tracking generator.

If you have other options installed in your R3131, I believe you will need to "Load" each one. If you have an R3131A, I read that there's an option to tell the CPU that you have the "A-type" version which restores the 10kHz span option. The password above appears to be the "default" password for the instrument.

Hope this helps others... I was without my Tracking Generator for over a year!

[cncjerry]

You are my hero! I've been worried about changing my battery and losing my TG. 

How can I ever thank you!?

[flolic]

I can confirm that above procedure for restoring options works 
My unit is R3131 with secondary RF input, which now works again. I also enabled "A" option, for R3131A and now minimum span is 10kHz.

One question. There is option for enabling RBW of 300Hz but on my unit it doesn't work correctly. Is there difference between 3131 and 3131A regarding RBW?

[cncjerry]

I have the RBW of 300hz on my R3131a and it works fine.  Maybe there is a real filter in the real A versions that is missing on yours?

[flolic]

I don't know.
In some user manuals there is 300Hz to 1MHz, and in some 1kHz to 1MHz  RBW, regardless of SA variant...
I can enable that option on my instrument, but displayed RBW looks more like 3kHz. I don't know if my unit just doesn't have that filter, or something is wrong with it.
Self test and calibration passes just fine.

[flolic]

So, I've took the cover of from my IF-LOG board and found what's wrong with 300Hz RBW option, -some parts (resistors, capacitors and diodes) are missing 
Those should be very easy to install, if I only know the capacitor values... At least I can read resistor values from hi res pictures from the first post.
What's interesting is that PCB part number is the same for 3131 and 3131A analyzers (BLL-023464), only my board is obviously from the first batch, it is 1997 Copyright.

[nair.sujith.v]

Firstly, a big thank you to marshallh & Marcel for solving the Total Gain failure on R3131A during self test. I now have the same problem.

So here is my question before I order parts and make the replacement:

1. Did replacing the 4072 opamps solve the problem for good or did it revert back in time?
2. Where is the MAX4106 located on the board? Is it underneath one of the shielding cans on the RF board? If so, which one?

Is solution 1 or 2 above a better long term fix?

Thanks,
Sujith

[nair.sujith.v]

Regards,

Marcel

Thank you very much. This solved my Total Gain failure after warm-up   

[IRB]

I have an R3131A with TG, after about 10 minutes the TG signal drops out.
I have pulled all the cards out of the chassis, and the power supply.
 Nothing appears burnt.
 Nothing smells burnt.
 Pass power up self tests.
 Passed self Calibration.
 
I put the power supply back in. I noticed voltages silk screened on the Buss PCB, on the side where the display was connected, behind the display.

                 J10   +5.2V   +12.6V    and    J9  -12.6V    +24V

I measure           +5.24V  +7.41                   -12.66V  +24.27

There is an unmarked pin on J9 that is 2.29V


The supply is marked AT120-5224/M NEMIC-LAMBDA
The supply looks like several switcher supplies in one.
I'm thinking it's a bad regulator.

I like to know if anyone has and can share a schematic for the power supply?
If anyone has a fixed a similar issue, and has advice?
 
Edit:
     I found a refurbished for $750 USD in Europe.
 
     I disconnected the CPU style fan and I have 12.6V.
     More testing needed. I hope it's just the fan.

[IRB]

I am thinking the Tracking Generator shutting down is unrelated to the 12V.

I have 12.64V at the Red wire to the LCD back-light. Still with the fan disconnected.
I also have a small fan blowing in to the case for cooling.
The T.G. went from -40dbm to -80dbm.
I ran the self test Shift 0 All tests pass.

Re-ran Self test, after I press the soft key to exit, the self test, the T.G. returned for a few minutes then
slowly dropped in amplitude.   

[nctnico]

Did you check the 12V power rail with a scope? It wouldn't surprise me if there is a huge amount of ripple on it due to a leaky capacitor in the PSU or another problem in the power supply.

[IRB]

I did not, now I have, it is clean less then 65mV ripple same on the 5V, using the frame as ground.
Measured with a Tektronix TDS220, using the cursor lines peak to peak.

[SaabFAN]

Summary of the problem-solving shown in the french videos that fixes the "Total Gain"-Error:

The problem lies in the variable gain amplifier INSIDE the RF-Section - The big, heavy block on the bottom module.

The OpAmp in question is U105 and the resistor that needs to be changed is R120.
As suggested in the Video, I changed the value from 390 to 470 and the error was gone.
Unfortunately, the video doesn't really show (I don't speak french and used the youtube-subtitles so I cannot say if he mentioned the exact location) where the OpAmp is located and how to access it.

You get access to it by removing the big bottom cover of the RF-Block. The RF-Gasket holds it in place even after the screws have been removed and requires a bit of force to come off. I used by fingernail as a wedge and lifted it in one corner by about a millimeter. Then the whole cover suddenly popped loose. So better have your other hand ready to catch it and prevent it from jumping up and falling back down on the PCB. Luckily mine took no damage.

The resistor is in the rear area with the green soldermask and can easily be replaced with a 0805 resistor.

A quick check of the analyzer afterwards revealed no immediate change in amplitude of the cal-signal - it was still about -9,7dBm, but to be sure, the analyzer should be properly calibrated after this procedure.

All in all, a rather easy repair, even though it requires disturbing the sacred RF-Block. But a nice prayer to the omnissiah to please the machine spirit and nothing should go wrong.

[Marcel G]

After a lot of reading on the internet and informing, I managed to replace a damaged 1st mixer of a Advantest R3131.
The original mixer (DMJ 4317-1) is no longer available but has found an excellent alternative by using an HSMS-2822.

Below you see two photos, one with the damaged mixer and a picture with the alternative mixer. Both photos were taken without any RF input. The differences are clearly perceptible.

Probably these diodes can also be used in other older Advantest Spectrum Analyzers, take advantage of them.

In any case, there is exactly the same mixer in the U4342 that I also have.

[cncjerry]

Thanks, keep the hacks and fixes coming.  I think this analyzer is underrated by the community.  I have a 3131a with TG and it is accurate and easy to use.  Paid $750 for it 5yrs ago, the guy wanted a heck of a lot more but i kept after him.  No regrets.

[nctnico]

AFAIK there are also issues with the analog switches.

[cncjerry]

whomever figured out the whole shift-9 password thing should get our equivalent of a grammy.  I tried it on mine last night and it worked perfectly.  What is an N-model?  There was an option to load it.  I have an "A" and my RBW goes a lot lower than others I've noticed.