Siglent SSA 3021X... Ooops

[Joel_l]

Hi,

I think I accidentally overloaded the input to my SA one too many times. My input impedance is no longer 50 Ohms. It still functions sortof.

I took the input board out and started looking around. I saw a 49R9 resistor which I assume is the termination resistor, it actually measures fine. I it looks like there are some clamping diodes on the input path and they seem fine. the input cap measures at 1uF, seems OK. Nothing looks like it got toasty.

The first IC in the input path is U1 a 956p, the 49R9 resistor is after that component in the path. Makes me wonder if that is the part I damaged.

I can't find any info on what that part is, anyone here know? Has anyone found schematics for this SA?

After some research, I believe the part is a GaAs MMIC. Still can't find a datasheet for the 956P to be sure.

Thanks
Joel

[tautech]

Hi,

I think I accidentally overloaded the input to my SA one too many times. My input impedance is no longer 50 Ohms. It still functions sortof.

I took the input board out and started looking around. I saw a 49R9 resistor which I assume is the termination resistor, it actually measures fine. I it looks like there are some clamping diodes on the input path and they seem fine. the input cap measures at 1uF, seems OK. Nothing looks like it got toasty.

The first IC in the input path is U1 a 956p, the 49R9 resistor is after that component in the path. Makes me wonder if that is the part I damaged.

I can't find any info on what that part is, anyone here know? Has anyone found schematics for this SA?

After some research, I believe the part is a GaAs MMIC. Still can't find a datasheet for the 956P to be sure.

Thanks
Joel

Sanity check:
Preset.
Connect TG to RF IN and apply -20dB TG signal.
Sweep should be at a -20dB level.

Post screenshot.

[Joel_l]

Its already in pieces. I was doing some tx measurements and left my attenuator out when making a change. The SA got 6 Watts pumped into it. It is not working properly now, levels are wrong, frequency is also off a little, I worry that might be a bigger issue. Measurements were fine until my screwup.

[Joel_l]

Looking at it more, I believe the parts 956P are switches. Looking at the path, it looks like the first switch switches in the 49R9 resistor, going farther down the path it looks like the other switches control some attenuators. Not sure why the 50 Ohm termination would ever be switched out.

[tautech]

Its already in pieces. I was doing some tx measurements and left my attenuator out when making a change. The SA got 6 Watts pumped into it. It is not working properly now, levels are wrong, frequency is also off a little, I worry that might be a bigger issue. Measurements were fine until my screwup.

Shame. 

Really we need screenshots to advise.
Normally damage to the front end results in 20dB error however I have one here that won't show any RF In levels. 

Here's one of a few mistake/damage threads:
https://www.eevblog.com/forum/testgear/what-happens-when-you-blow-the-input-of-a-6500-siglent-ssa-3075x-plus!/