Rigol DSA-815 repair

[NortliW]

Hi all,

I'm trying to repair the front-end of the well known Rigol DSA815. It had too much RF power. I managed to replace D106 with an RN152G wich was damaged. The Noise level of the analyzer is about 17dB higher than it used to be. Anyone has ever faced this problem? I presume the rf-switch U100 is damaged as well (and maybe U101?) but there is no code on the case because Rigol lasered it away. Who has any parts list or schematic or knows what type of rf-switch this is? I could try the AS179-92.

Any comments or suggestions welcome. TNX,

B.

[cncjerry]

Most of the time when a spectrum analyzer takes too much power the first mixer is damaged.  I assume you put a signal into it.  Does the amplitude of a known signal look correct except for the noise?  I don't remember if that has a preamp in it. You might be able to terminate or ground the input prior to the mixer to see what the noise level looks like at that point.

[NortliW]

Just the noise level is lifted the rest is all fine, even the amplifier is working and brings up the level of the measured signal. If a mixer is being damaged most of the time your output signal looks distorted or the level is not correct.

[TurboTom]

The Switches U100 and U101 are most probably Hittite HMC221B. The ESD protection diode (D106) can be substituted with an Infineon ESD113-B1-02EL (3.3V) or possibly an ESD0P2RF-02LRH (5.3V). The first step attenuator likely is a Peregrine Semiconductor PE4302 and the preamp switches are Hittite HMC284MS8G / GE. In order to replace the two latter components, professional SMD rework equipment is required since these components have exposed pads at their bases.

I wouldn't expect anything else to have failed since you reported the mixing products to be reasonable. Good luck with the repair!

Cheers,
Thomas

[NortliW]

Replaced the two switches for HMC221's and the dynamic properties are back but unfortunately the level of the measured signal is not right and consistant over frequency. Maybe I did not measure that very acurate before the swap. The two more HMC284's will be replaced next. Hope that will help.........more to come.

[TurboTom]

If you've still got the RN152G as the input limiter installed, I would recommend to remove it and CAREFULLY test the analyzer completely without input protection. I'm pretty sure Rigol didn't put a PIN diode in that place but rather a "proper" bi-directional RF clamping device. I mentioned two options in my previous mail and the PIN diode could very well distort the level since it will act as a rectifier at the lower frequencies. And removing this 2-terminal device is a much easier task than replacing the HMC284's with their exposed pad enclosures from a multilayer with substantial ground planes... Moreover, I wouldn't expect the HMC284 switches to be defective since they are located behind the step attenuator. So if there's actually further damage to the DSA, I would rather look at the attenuator.

Cheers,
Thomas

[NortliW]

Hi Tom,

We got it repaired, replaced all the switches, first mixer and the diode and now it is working fully within specs. We removed all components with hot air and just reflowed new ones in one at the time. It came back to life piece by piece.

Thanks for your support and if anyone want it to be repaired just give me a shout. TNX.


B.

[TurboTom]

Congratulations on your success! Damage to RF components can have quite surprising effects, often just degrading their performance and not rendering them completely inoperational. Did you use the HMC213A as a replacement of the mixer? Anyway, it's good to know that even substantial damage of the DSA815`s RF front end isn't a death sentence for the instrument but can be repaired. Well done!

Cheers,
Thomas

[Mosaic]

perhaps a list of the replacement parts and the sources for them will help others here?

[JoeO]

perhaps a list of the replacement parts and the sources for them will help others here?

Yes, in addition if you made a partial schematic, please include that.

[Wall-E]

For some useful information for someone interested in repairing a DSA815 RF or IF issue, or just understanding more about the RF and IF system of the SA section:  https://www.eevblog.com/forum/testgear/spectrum-analyzer-rigol-dsa815/msg1059060/#msg1059060

[onkelpepi]

Here my DSA815 repair story:
Symptoms started with "IF out of range" messages and sudden calibration which took up to hours. During calibration, the analyzer showed a weird spectrum, even without any source connected. This issue suddenly disappeared and the Analyzer worked fine for a few weeks. Then it started to reappear intermittently. It also happened during startup. The analyzer remained in "Device initializing..." for up to 3 hours. Another issue was loss of TG normalisation every now and then. Whenever I opened the analyzer and attempted to repair it, it started to work normally after digging around a while. Finally, it did not show any spectrum anymore. I first thought that I killed the front end, but when it happened, there was no signal applied which exceeded the input ratings.
Upon opening, I found a cracked (and electrically shorted) tantalum capacitor next to the 3rd IF section - 47µ/35V. After replacing it, the analyzer worked fine again. Seems the capacitor degenerated gradually until it finally shorted out. Attached a picture of the culprit.

[mcinque]

perhaps a list of the replacement parts and the sources for them will help others here?

yes, please!

[ted572]

List of DSA815 RF Front-End/IF Components
https://www.eevblog.com/forum/testgear/spectrum-analyzer-rigol-dsa815/msg1059060/#msg1059060