R&S SMIQ 03B Standbay/ON error

[Aleksandar]

Hi to all,

I need help from someone who knows the hardware very well in SMIK 03B.
I bought the SMIQ03B on the ebay and after the transport of several thousand km, the SG does not accept Standby/ON switch, on the front. Svitch is OK.
Only the light diode. I trust to the seller, that the device was right before.
Two fuses  inside power supply block are OK.
The service manual  (downloaded ) VOL3 is very scarce. Also, Serial No. of the power supply unit and service instructions are different.
Although I believe that in this case there is no relevance.


Every advice is welcome

I'm sorry about the bad Google English

[Aleksandar]

Hi,

Problem with switcher Standbay/On is solved. One connector was slightly disconnected. Maybe 1mm to 2mm. It's the upper end.

Unfortunately, after that, I established a list of errors. Pictures are attached.
On the forum I found solving of the problem  with ALC Error 110 for SMIQ 06. Did anyone have similar problems with SMIQ 03B?
What does  mean: Error:reference voltage oot(6.9 ... 12.0V)?

Thanks

[CJay]

I'd suggest something else has been dislodged in transit, might be worth, if you haven't already, reseating all cards and modules.

[Aleksandar]

No, I did not. The trial does not cost anything!

[Aleksandar]

Is there some table where voltages can be compared with voltages in UTILYTIES / DIAG / TPOINT mode?

[Aleksandar]

Hi,
The answer to my question, where there  are the regular voltage values  from: UTILYTIES / DIAG / TPOINT mode, I found in the Service manual, Vol1, page 17, chapter 1.4.4 List of diagnostic points. It can be still  of use to someone!

[sorenkir]

Hi,

This thread deals with an ALC error 110 on a SMIQ03B:
https://www.eevblog.com/forum/repair/rohde-schwarz-smiq03b-with-error-110-output-unleveled-iqmod-alc-failure/

In that case, the final amplifier IC was dead.
Michel.

[Aleksandar]

Thanks Sorenkir,
I found that tread about it.

I have a maximum level of -10dbm with + 5dbm at SMIQ, with the AUTO MODE attenuator. Above this level on the SMIQ I do not have a higher level on the RF OUT (with TEK492Analyzer).
Below is a possible adjustment. The level of 0dbm corresponds to RF OUT of -15dbm, -5dbm corresponds to RF OUT -20dBm, etc.
Does this data indicates something.

[DaJMasta]

Is that the actual behavior, or just predicted?  When I was working on the same error on the 6GHz extension, the output power would raise as you increased it until the next attenuator step kicked in, then it would drop down again - not a fixed offset that would look like a linear function, but more of a stepped thing as it tried to get up to level on the high end and settled more on the low end of the attenuator step range.


If you suspect anything with the attenuator or panel connectors, you can probably locate the output SMA on the bottom of the cards and connect your analyzer directly to there, then no matter what the attenuator is doing, you get the signal before it goes into there.

[Aleksandar]

This is real behavior.
The negative offset is 15dbm. But I can not raise the RF OUT level above -10dBm. When I set + 10dbm to SMIQ, I still have -10dbm at the output.

Something else.
For example, at 100MHz, the second harmonic (200MHz) has only a 6dbm lower level.
What do you think, is this related to the previous problem or an independent problem?

For the weekend I will have time to open the SMIQ and start the search in this section.
Any kind of interesting observations, I will post on the forum.

[Aleksandar]

When I wrote for harmonic today, I remembered  that I had another instrument at my home, called an oscilloscope :-)

The attached picture is the answer to my question, why there are big harmonics.
My so long awaited signal generator is actually, the pulse generator :-(

My belief in good shopping, every day becomes more and more misleading

[sorenkir]

I think it's time to see what's happening inside!
First as, DaJMasta has said, you should check the signal before the mechanical output attenuator (only one cable to disconnect).
And then, if you remove the cover of the IQ-Modulator board (block function and position is printed on the cover), put it back in place without cover and detach the front panel, keeping it connected, you can have (limited) access to the board and probe to trace back the signal through the various amplifier stages.
Michel.

[Aleksandar]

Thank you Michel,
Finally, I gotta get inside the box!!

That's right. I thought it was a weekend, but I was out of the house.
I will unplug the semigrid cable from the bottom of the I /Q-Modulator board and directly attach to the spectrum analyzer.
Should I expect a maximum output level of + 13dbm?

This part of the job is very easy compared to the one that follows!?

[Aleksandar]

Hi, Michel,

The RF level is the same before and after the attenuator, -10dBm.
One note. In ALC-ON, and ATTENUATOR MODE AUTO, I have only 5dBm attenuation step, nothing between.
So, I/Q-Modulator!?

[sorenkir]

And what about distortion ?
If the attenuator is OK, maybe you should first try to trace back the signal in the IQ-Modulator block starting from X249 by probing with your scope (for amplitude and distortion).
In the attached image, the two final MMIC amplifiers are circled in red (in my SMIQ they are NLB-400 and SHF-0189 amplifiers).
Michel.

[Aleksandar]

Thank you, Michel.
I'll look at this route with oscilloscope.

But my output stage is significantly different from yours. Look at the picture.
I have the first two MMICs labeled H1 and the third, which differs in the case, also labeled with H1.
This third, I think it's like your SFH-189.
And what are the first two? And maybe it does not matter now!

Also, I noticed that for all three amplifiers there are general purpose PNP transistors for polarization (BSP31), whose configurations at first glance is exactly the same.
For the first two, I'm sure.
However, measured with ordinary DMM, the difference on the pins B, E, and C is drastically different. For A1, C-E=39 Omhs, independently of the polarity of the DMM. BSP31 for A2 has about 55kOhms.
Below, on side B, there are two op amp TL074. These OP amps  probably controlled these transistors. Thay have  the same configurations. But they, also have different ohmic values!
I think that one TL is bad, since I have checked the transistor.
I'll be back when I get this op amp.

Another thing, do you know which component is in white plastic, marked with W1. Mixer, combiner ...?
I can not read the label on your picture.

73
Aleksandar

[Aleksandar]

I found what was first two RF amplifiers with the H1 mark. These are, GaAs HFET SHF-0186K.
Details are attached.

[sorenkir]

May be you have the older version described in this document http://www.ko4bb.com/getsimple/index.php?id=download&file=Rohde_Schwarz/Rohde_Schwarz_SMIQ-XX_Service_Manual-Vol2.pdf page 186.
Parts list is page 259.
You can check some voltages and operating points --> page 207-208.

I don't know exactly about W1, probably a switch.

Michel.

[Aleksandar]

First, thank you Michael for these notes.
I have I/Q Modulator with mark 1084.9800.08

I now know what is W1!
Exact is your assumption, that is the SSW-124, GaAs FET MMIC switch.

After several days, I found the time to look again the output stage with an oscilloscope.

After the first amplifier V144, the pure sine wave signal. The signal is amolified from the input to it.
After the second V103, too. Amplitude 1.4Vpp on the drain. Very clear sine wave.

Unfortunately, after the third amplifier, the V104, (GaAs HFET SHF-0189), signal is weakened and significantly deformed. Image at previous post.
The DC voltage on the drain is 630mV. In the service manual Vol2, chapter 7.4.8, the voltage on the V104 should be 7.3V.
I suppose that is bad last amplifier, transistor  V104, SHF-0189?
Since the purchase of this transistor is a complicated job for me, I will not have the opportunity to post a minimum of 2o days.

Greetings to all

[Aleksandar]

I need to make one correction and some updates!
RF voltage on the drain V103 is 3.3Vpp, and not 1,4Vpp. My mistake in rewriting.
RF voltage on the gate V104 is 2.7Vpp
RF voltage on the drain V104 is 600mVpp and significantly deformed.

I measured DC voltages at V104:
DC voltage on the V104 is -99mV
DC voltage of the V104 is 524mV

When I look at these voltages, Vgs and Vds, I ask my self, whether the V104 deeply saturated or broken?
A gate bias -99mV is very litle
I think it should be about -1V, maybe -1.2V
Could it be a problem in the circuits for a gate bias?
I do not have a serious experience with these transistors

[sorenkir]

Hi,
It looks to be the same failure than on mine.
To make sure that it is not the biasing circuit that is defective, you could try the same method as me:
https://www.eevblog.com/forum/repair/rohde-schwarz-smiq03b-with-error-110-output-unleveled-iqmod-alc-failure/msg855948/#msg855948
Michel.

[Aleksandar]

Hi Michel,

Very, very similar malfunction!
Since you have a positive experience with this Utsource, I'll try to order them  the SHF-0189!

For each case, three pieces :-)

Aleksandar

[Aleksandar]

Hi to all,

I replaced SHF-0189 and ALC ON ERROR disappeared.
Max output level is + 16dBm. Level control is OK.
And I am happy with this New Year's gift!

Thank you to all who gave me advice.

Merry Christmas and Happy New Year

Aleksandar