Siglent SSA3021X Plus frontend

[Bastifantasti]

Hi everyone!

Recently i have some strange behaviour on my Siglent SSA3021x Plus and i think i killed my frontend. The SA didnt show any signals except some noise at about -60dB as if nothing was connected. I tried it with the TG, but still nothing. If i change the TG from -20dB to 0dB the line will go up a little bit. The TG seems to be ok since i could measure a sine wave with the oscilloscope. I found some threads here and the video about repairing the RF switch in the frontend. So i replaced the first RF switch HMC1118 but without any positiv result. So in the next step i also changed all three MASWSS0181TR-3000. I connected a signal generator to the input with a few MHz signal and could measure the signal on the PCB without any significant attenuation on all switches. I could also measure 50 Ohms on the input with my NanoVNA.
Now the display shows my MHz Signal but it wont go beyound -40dB. If i switch on the 20dB preamp, the baseline will go up but the peaks wont go higher than about -40dB. So it seems the signal is cut at about -40dB. With an antenna connected or a near field probe i can see almost nothing.
Do you have any ideas where else i could have a closer look? Could it be a software related issue? Btw, i also did a factory reset, but without positive results.

 

[MathWizard]

What does the self-diagnostic say ??

[Bastifantasti]

I only know about the self-test option to test buttons and the touch Display.

[coromonadalix]

had a recent failure on a ssg3k model,  tons of tons of screws to remove

yes  an HMC1118 failed, i may have spiked it ...  you reeally need to dig out all the parts in the signal pathways, find the datasheet(s) if possible,  i had 3x or 4x  signal attenuators on the path, but where fine    etc ...    and the HMC1118  at the end / output  was dead

followed the signal  with a scope and minimum x10 probe to have an high impedance ... it was easy to kill the signal while probing

I was sad to see many output protection parts not installed  ...

[MathWizard]

Ok I'm thinking of old Tektronix stuff. Lots of stuff still has error codes, so does Siglent have any that the user can see ? What about the other big brands these days ??

[Bastifantasti]

No, unfortunately no error codes on these problems. Maybe for the digital stuff, but no error codes for the analog parts.

[Bastifantasti]

Any other ideas on this? We already replaced all hf switches in the frontend. Could it be the mixer or the second amplifier.
I attached some screenshots of the signal with -6dBm on the input.
The first one is with 5dBm atten. and preamp on. The second screenshot is with 16dBm atten. and preamp off. The third one also with preamp off and atten. off. As you can see the signal will never go above -60dBm.

[tautech]

Sanity check test:
Connect TG to RF In
Set TG level and check the same level is displayed, disregard non-flatness for now....could be + 3dB.

Show screenshot.

[Bastifantasti]

With TG i see almost nothing. The base line will go up a little bit, maybe 2 or 3 dbm, but still under 100dbm.

[tautech]

With TG i see almost nothing. The base line will go up a little bit, maybe 2 or 3 dbm, but still under 100dbm.

Press Preset to set default settings.
Connect TG to RF In and set TG to ON.
Show screenshot with TG menu visible.

[Bastifantasti]

Hi,

i attached some screeshots.
1st iamge: screen with nothing connected and after Preset / Factory reset.
2nd image: TG on with default settings.
3rd image: TG on with TG Level 0dB

[tautech]

Screenshots are perfect, a picture saves 1000 words.

Okay 40dB down is not good. 
Damage to HMC1118 usually accounts for a 20dB error.

Keep studying threads for clues on such large errors.....

[Bastifantasti]

Could it be the mixer or would i see absolutely nothing if the mixer were damaged? The mixer and the amplifier are the next parts in the chain, which i didnt replace. I would give it try, unfortunately the mixer ist quite expensive.