Electronics > Repair
Rohde & Schwarz SMIQ03B with Error 110 Output unleveled; IQMOD: ALC failure
jgorsk:
I managed to find a few faulty components. The FET at the output from IQCON board and a few amps in the 300MHz
vector modulation signal path were faulty. CW, analog and digital modulations work now but there are still a few errors left.
They are
-313 calibration memory lost; LEV_PRESET
-313 calibration memory lost; VECTOR_MOD
-313 calibration memory lost; LEVEL_ATT
LEV_PRESET calibration fails with 'IQCON no convergence' error message,
VECTOR_MOD and LEVEL_ATT calibrations fail with 'Reference voltage oot (6.9 ... 12V)' message.
In vector modulation mode with no I/Q signals applied the carrier level is about 20dB below the setpoint.
Is the carrier supposed to be suppressed in this mode or should it be as set by the level setpoint?
analogRF:
--- Quote from: jgorsk on October 11, 2016, 07:14:16 pm ---I managed to find a few faulty components. The FET at the output from IQCON board and a few amps in the 300MHz
vector modulation signal path were faulty. CW, analog and digital modulations work now but there are still a few errors left.
They are
-313 calibration memory lost; LEV_PRESET
-313 calibration memory lost; VECTOR_MOD
-313 calibration memory lost; LEVEL_ATT
LEV_PRESET calibration fails with 'IQCON no convergence' error message,
VECTOR_MOD and LEVEL_ATT calibrations fail with 'Reference voltage oot (6.9 ... 12V)' message.
In vector modulation mode with no I/Q signals applied the carrier level is about 20dB below the setpoint.
Is the carrier supposed to be suppressed in this mode or should it be as set by the level setpoint?
--- End quote ---
did you ever managed to fix the 'IQCON no convergence' error?
zmetzing:
Schematics for the 1084.9800.01 IQ Modulator board, among other things, are located here:
http://eww.ko4bb.com/getsimple/index.php?id=manuals&dir=Rohde_Schwarz
I'm currently diagnosing my SMIQ 03B's failure "ERROR: CW: ALC_ON voltage oot" during CALIB ALC TABLE. The SHF-0189Z final has been replaced, as a shotgun-debugging start. (That was a booger to get out. Hot air @ 375C plus my Metcal on the back tab.) Didn't fix the issue.
Extender cards seem to be unobtanium, so I'll take the advice of others here and pull the front panel so I can have limited access through the front of the machine.
zmetzing:
Looks like the output is fairly low, so it points to the output stage.
For reference, my 8568A's 20MHz -10dBm reference signal into a Iwatsu 470 MHz analog scope (50 ohm input) shows 200mV p-t-p at 20MHz (correct).
However, the SIMQ's output shows only 100mV p-t-p at 20MHz when set for +10dBm. This is -16dBm.
Handy table here for dBm -> mV (50 ohm) here http://wera.cen.uni-hamburg.de/DBM.shtml
(Yep, I'm a noob at this forum software)
charlyd:
can this help you:
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