Rohde & Schwarz Signal Gerator SML-01 - Need Help Repairing

[rshuler]

Hi,

I have a Rohde & Schwarz Signal Generator SML-01. The unit is in good condition, and has a good display.  However, the output is about 1/5 of what it should be at all frequency.  In addition, the output signal is not very symmetrical as the amplitude is increased. As the amplitude increases, the output has a minor flatting on the negative half of the cycle at max amplitude. 

The LF Signal Output is okay. 

The unit passes internal calibration.

Any experience or ideas on how to repair the unit's RF Signal Output would be a great help.

[oldway]

Wellcom on the forum.

You can download the service manual here:

https://elektrotanya.com/rohde-schwarz_sml01_sml02_sml03_vol2_signalgenerator.pdf/download.html

Wait for"processing" became "get manual".

But there is no schematics....

[Armadillo]

Check the negative power supply voltage.

[rshuler]

Hi,

While probing the pulse generator module rf path, I notice that the signal distortion was in the third stage of the rf path. I'm not sure what is causing the signal distortion.

I by-passed the pulse generate.  Now the output looks better, and the signal amplitude increased; however, the signal level is now approximately, 8db low.  When the output is set to 0.0 dbm, the spectrum analyzer see around -8 db.

I checked the attenuator, and it looks okay.  It looks like the signal entering the attenuator is low.

Does anyone know how to calibrate the SML-01 or adjust the output power on the mainboard (before it gets to the attenuator)?

Thanks,
Robert


 

   

[CrazyTiger]

Hi,

Please do check the following:

1. Power Supply and Power Supply Cable, SML series has a crappy power supply connector cable assembly, the contact pins tends to cook from the inside increasing contact resistance.

2. Try taking the measurement directly from the output stage/mainboard of the sig.gen, usually when the sig.gen is set  0dbm, it should give at-least 10dbm or higher, if this is about there,then the problem will be most likely the pulse modulator or the attenuator.

Good Luck

[charlyd]

in an other topic i am looking for the software to calibrate and test
if i am right SML-Z2 it is called.

[George Edmonds]

Hi

There are copies of the SML-Z2 calibration software on the internet, BUT it requires some very specific hardware:-

NI GPIB controller in a PC.
GPIB cable.
R&S NRVD power meter.
R&S Z51 power sensor for the NRVD.

The killer is the Z51 power sensor, these are about as common as hens teeth.  NOTHING ELSE WILL WORK WITH THE SOFTWARE.  If you can find them the NRVD power meter plus the Z51 sensor will cost you more than the SML-01

G Edmonds

[I4E]

We have a R&S NRV- Z51  Power sensor in stock and NRVS Power Meters. 



Joy Torres
Instruments 4 Engineers Ltd
https://www.instruments4engineers.com/

[George Edmonds]

Hi

An NRVS will not work it has to be an NRVD

G Edmonds