What happens when you blow the input of a £6500 Siglent SSA 3075X Plus!

[inaxeon]

Hello Community

Only a month after having purchased it, I've made the unfortunate mishap of damaging the input of my new Siglent 7.5 GHz Spectrum Analyser. Basically once I did this the warranty is toast. I was quoted EUR 3200 to fix it (they just replace the whole RF deck). Ridiculous. They helpfully linked me to this video:



And told me I could try repair it myself. Thanks. Not.

So instead I'm going to pull it open and see if I can sort it out. There's no pictures of the inside of one of these I could find so this should be interesting.

A first look reveals that it is a completely different instrument inside to the 3GHz models. Looks like it's setup for VNA too but I can't see any official upgrade for that yet?

After undoing 1000 plus screws I'm "In like Flynn". The main RF deck is a completely different design to the 3 GHz models.

I'm goint to start off by replacing the first, and maybe second RF switch. There ain't much else in there and see how that goes. It's an HMC1118.

[Grandchuck]

As they say, "What do you have to lose?"  Good luck.

Years ago, I forgot the dc block and damaged a spectrum analyzer.  Some mistakes are soooo painful!

[inaxeon]

I blew it with an RF current probe. No DC involved here ;-)

[rf-loop]

And told me I could try repair it myself. Thanks. Not.

So instead I'm going to pull it open and see if I can sort it out.

Here is now some logic what I can not understand.

You did not want do it using Siglent help but after then you want do it just with your own?
I am guite sure if Siglent told you can also try repair it yourself, naturally after then they may also give some helpful instructions for it, perhaps perhaps even more...
 
Least I have been in this situation (exept that reason for failure was unknown but propably ESD to input connector) with other SA model and I get all needed instructions for diagnose and also for repair, they sent even needed components (rf switch and some pin diodes).

[inaxeon]

I did ask for technical details. I got this:

However I´m not allowed to provide much information about the device, therefore I added the link to the video from Shahriar.

So basically EUR 3500 or chance it.

[voltsandjolts]

It's an HMC1118.

Well, hope that fixes it for ya. If only you could fit an IC socket for next time

[wraper]

I wonder how they determined that fault is not covered by warranty?

[nctnico]

If J20 is the input then it seems the input has a DC block incorporated. It is strange that the input goes straight into a chip without any ESD protection. A better solution would be to have a good old relay operated attenuator before any semiconductors. My Advantest spectrum analyser defaults to having a 10dB attenuator enabled in order to have some input protection. It can be disabled but this is only necessary for measurements that needs the extra sensitivity.

[inaxeon]

I wonder how they determined that fault is not covered by warranty?

It could be due to the fact that I blew it by being a dumb arse... It's not like they don't say it a 1000 times when EMC testing to protect your spectrum analyser. The connector I had powering the DUT was loose, causing a power cycle during testing which popped it.

[inaxeon]

If J20 is the input then it seems the input has a DC block incorporated. It is strange that the input goes straight into a chip without any ESD protection. A better solution would be to have a good old relay operated attenuator before any semiconductors. My Advantest spectrum analyser defaults to having a 10dB attenuator enabled in order to have some input protection. It can be disabled but this is only necessary for measurements that needs the extra sensitivity.

J20 is the input from the FP. I don't think it's -that- strange. They likely didn't want to pay the performance price of protecting it.

[nctnico]

An external attenuator (10dB) or RF limiter is a good idea to use together with what is -essentially- an open input spectrum analyser.

What you can try is to remove the first HMC1118 and feed an RF signal into the next stage (which seems to be an attenuator circuit) to see if only the first stage is broken.

[inaxeon]

What you can try is to remove the first HMC1118 and feed an RF signal into the next stage (which seems to be an attenuator circuit) to see if only the first stage is broken.

I was thinking that, and was very tempted to -but- for the cost of only £12 I'd prefer to chance it. If I start experimenting it increases the number of times that area is reworked, and the chances of damaging the PCB.

[coromonadalix]

hum    could the eevblog member   or signal path member   do a checkup on it ??

They are good in trouble shooting signals path  etc ...   send them an Email ??

[inaxeon]

hum    could the eevblog member   or signal path member   do a checkup on it ??

They are good in trouble shooting signals path  etc ...   send them an Email ??

Hopefully I shouldn't need to. I already did a bit of testing on it. Superficially the digital attenuator (HMC424) and preamp appear to be still working OK. What I see is a fixed 40dB of attenuation on the input, so it is quite likely that it's one of the switches. Have ordered a couple more to try out.

But I could be wrong. Will find out in due course.

[tautech]

I did ask for technical details. I got this:

However I´m not allowed to provide much information about the device, therefore I added the link to the video from Shahriar.

So basically EUR 3500 or chance it.

Let me see if we can get some better guidance for you. Might take a day or so.

[tautech]

I wonder how they determined that fault is not covered by warranty?

It could be due to the fact that I blew it by being a dumb arse... It's not like they don't say it a 1000 times when EMC testing to protect your spectrum analyser. The connector I had powering the DUT was loose, causing a power cycle during testing which popped it.

Did you have the Preamp ON ?

[inaxeon]

Did you have the Preamp ON ?

It was at some point but I think I switched it out just before the incident. I it does still seem to be providing a consistent 30dB gain of what left I can get from the input - which is attenuated by 40dB or so. I -think- it's OK.

[tautech]

Did you have the Preamp ON ?

It was at some point but I think I switched it out just before the incident. I it does still seem to be providing a consistent 30dB gain of what left I can get from the input - which is attenuated by 40dB or so. I -think- it's OK.

Typically we would leave attenuation settings to be auto managed and have Preamp ON for EMI work when using a noncontact RF probe.
Where you in EMI mode when the incident happened ?

[inaxeon]

Did you have the Preamp ON ?

It was at some point but I think I switched it out just before the incident. I it does still seem to be providing a consistent 30dB gain of what left I can get from the input - which is attenuated by 40dB or so. I -think- it's OK.

Typically we would leave attenuation settings to be auto managed and have Preamp ON for EMI work when using a noncontact RF probe.
Where you in EMI mode when the incident happened ?

Not in EMI mode at the time. Manual attenuation 10dB.

[tautech]

Did you have the Preamp ON ?

It was at some point but I think I switched it out just before the incident. I it does still seem to be providing a consistent 30dB gain of what left I can get from the input - which is attenuated by 40dB or so. I -think- it's OK.

Typically we would leave attenuation settings to be auto managed and have Preamp ON for EMI work when using a noncontact RF probe.
Where you in EMI mode when the incident happened ?

Not in EMI mode at the time. Manual attenuation 10dB.

Hmmm, did the RF input overload warning sound ?
From the datasheet:
Maximum average power: 30 dBm, 3 minutes, fc ≥10 MHz, att > 20 dBm, preamp off
Maximum damage level: 33 dBm, fc ≥ 10 MHz, att > 20 dBm, preamp off

[inaxeon]

Hmmm, did the RF input overload warning sound ?
From the datasheet:
Maximum average power: 30 dBm, 3 minutes, fc ≥10 MHz, att > 20 dBm, preamp off
Maximum damage level: 33 dBm, fc ≥ 10 MHz, att > 20 dBm, preamp off

No buzzer. Wouldn't expect it on a transient, would you?

[tautech]

Hmmm, did the RF input overload warning sound ?
From the datasheet:
Maximum average power: 30 dBm, 3 minutes, fc ≥10 MHz, att > 20 dBm, preamp off
Maximum damage level: 33 dBm, fc ≥ 10 MHz, att > 20 dBm, preamp off

No buzzer. Wouldn't expect it on a transient, would you?

No, however the more info you provide the better a diagnosis plus more importantly this all serves as help for those that might have a similar issue.
Dealing with issues like this on a public forum provide a long lasting record that can help others many years down the track.
On of the most knowledgeable on SSA's is rf-loop whom replied earlier with some pertinent points. Like he experienced, let's see what Siglent HQ advise.

[TurboTom]

If you look at the HMC1118 datasheet, it quickly gets obvious that Siglent's overload specs tell only half the truth. They appear to be valid for frequencies of 10MHz and up, but below, there's a steep drop of the damage threshold of these switches as it seems. At a few tens of kilohertz, this limit can be as low as 10dBm. And a wonky power connector for sure may produce signals in this lower frequency range. An additional LF/DC block may be a good insurance to prevent similar "oopsies" from happening in future.
Anyway, good luck with the repair and thanks for sharing the information on the 7GHz SSA!

[eti]

Hello Community

Only a month after having purchased it, I've made the unfortunate mishap of damaging the input of my new Siglent 7.5 GHz Spectrum Analyser. Basically once I did this the warranty is toast. I was quoted EUR 3200 to fix it (they just replace the whole RF deck). Ridiculous. They helpfully linked me to this video:



And told me I could try repair it myself. Thanks. Not.

So instead I'm going to pull it open and see if I can sort it out. There's no pictures of the inside of one of these I could find so this should be interesting.

A first look reveals that it is a completely different instrument inside to the 3GHz models. Looks like it's setup for VNA too but I can't see any official upgrade for that yet?

After undoing 1000 plus screws I'm "In like Flynn". The main RF deck is a completely different design to the 3 GHz models.

I'm goint to start off by replacing the first, and maybe second RF switch. There ain't much else in there and see how that goes. It's an HMC1118.

So you’re complaining that the device *you* damaged, and are reticent to have them repair for such a high cost, the same one for which they’ve kindly shown you TSP channel video for, to help you repair it and save you money? Nice. They didn’t HAVE to share that video with you. 

[TheSteve]

Any chance you checked the impedance of the front end with a VNA before disassembly?
Replacing the first HMC1118 will hopefully fix it.
If you're not super comfortable with hot air rework I recommend timing how long it takes to remove the original IC so you can use the same heat/time when installing the new one. Obviously you want to use as little heat as possible but it will probably take quite a bit.