Repair of Anritsu S332D

[vishaldotgupta]

please check with DMM that tuning voltage on VCO varies as equipment sweeps.

if not check around PLL IC for clock, voltages, charge pump, and associated driver circuit which mostly consists of OPAMPS like LT1078

[jasony_ng]

hey, guys, I had successfully repaired my S331C by replace the E3 mmic amplifier for "integrator failed", and some 50ohm chip resistors on input port.
I looks your photos, I think it should be on the place as my red circle marked.

[rainbow]

Sorry if I add a little different model S331B to the discussion but this thread seems covering the S331/S332 lines.
My device pass all self tests (from the menu and from the booting) but the sweep is very very slow and at each step the "Integrator Failure" icon appears. I think that the problem is in the latest stage near the output connector since it is not verified by "self tests" and the slow sweep is because it is waiting the return signal. What do you think? Someone has already encountered this problem?

thank you

ps. In attachment the photos of the RF input.

[rainbow]

I did a few more tests to try to split the problem:
- the "integrator failure" icon is more present if the frequency is lower than 900MHz
- after ~1700MHz the instrument seems to work correctly and "integration failure" is very rare
- at low frequency the signal in CW mode is intermittent
- the output signal from N port has low power at low frequency (see images from spectrum analyzer) when in CW mode. How much should be the signal power in CW mode when the instrument is working?

With an active probe and the spectrum analyzer I measured the following test point (I don't know if they are the same of the other boards)
- TP40: -41 dBm CW signal
- TP29: -50 dBm CW signal
- TP19: -52 dBm CW signal and 8V DC
- TP14: -52 dBm CW signal
- TP13: a lot of noise without any preponderant signal

I measured the white "Bc" component that I suspect is a two/three ways PIN diode (ports are numbered A, B and C from the top clockwise)
STATIC:
- diode 0.7Vf from A to B with 8M resistance
- diode 0.7Vf from A to C with 64K resistance
- diode 0.9Vv from C to B with 8M resistance
DYNAMIC:
- each port show low frequency square wave (it is probably the switching DC signal but I haven't superimposed two ports)
- port A 2Vpp square wave the other ports has 100Vpp

[jasony_ng]

Here is the S331C RF output on CW mode, it value around 0~-5dbm

[vishaldotgupta]

integrator fail and slow sweep is generally due to faulty RF Switch, Attenuator or amplfiier.

to verify connect a spectrum to the output and put the equipment in zero span and check the level of signal on spcectrum.

ideally it should be close to -10dBm.  if it is missing then amplifier is faulty.  if lower by say 20dB, then attunuator or rf switch is faulty.

if the singal is there but at some other frequency probably issues are there with PLL , reference clock, VCO etc

anritsu uses different versions of boards for same model, some of them may or may not have switch or attenuator etc

swi in picture is the switch. amplfiers are under the metal lid

hope this helps

[rainbow]

Thanks to everyone for the support. Seems that the last MMIC (mini-circuits ERA-3) is faulty. Now I order a replacement and I will check if the values are correct.

[Boofrmb]

Hi All.
Hoping someone may be able to help me get my S331A back up and running.
All appears ok, but when I start the machine up, I have to adjust the contrast everytime, and then I get a "PLL fail" during the self test.
Any ideas where to stay would be great, or even where I maybe able to obtain a cct.
Thanks in advance.
Robert

[Boofrmb]

Have added this section of the S331A, PLL section

[Boofrmb]

Complete S331A board.

[Boofrmb]

Here is the board