Hi,
We just got a UPV back from an extensive service @ R+S. As it's discontinued and we are concerned about how long R+S will support it for, we decided to go for the full repair option, inc. 1 year guarantee (big hole in wallet).
The machine works like a charm and has the latest firmware (good). However, when either of the oscillator options are fed to the analyser (standard oscillator, B1 or B3) there is a 50Hz spike on the FFT (it goes from below -150dBV to around -120dBV). I shorted the I/P and flipped between analogue IN / gen 1 / gen 2 - and you can see the 50Hz is not there with shorted I/P and only present when loopback (or XLR leads from I/O) are used. Our other UPVs offer -113 THD+N with 2VRMS, but the serviced one only has -111 THD+N. If I feed it from another oscillator, it's cool, so the issue is isolated to the UPV output section.
My feeling is that a shield isn't grounded or a screw has been left out - that kind of thing. I am loathe to open the thing as it has a 1-yr guarantee. I am wondering if R+S will give us special dispensation to open it, assuming that there is an obvious instruction to fix it (hence my post here, to ask if anyone has taken one apart and can think of an obvious culprit?). It would be a bummer if we have to send it back to Germany just because someone left out an insulating washer...
They swapped the entire analogue board during the repair - repair report here:
The irony is that one of our UPVs was constructed out of a pair of totally broken UPVs (by us) that we bought for parts - and it has no 50Hz to worry about! We had front panel and keypad changed on the problem one, so it looks and feels like new....aarghh...
Any tips appreciated!
We just got a UPV back from an extensive service @ R+S. As it's discontinued and we are concerned about how long R+S will support it for, we decided to go for the full repair option, inc. 1 year guarantee (big hole in wallet).
The machine works like a charm and has the latest firmware (good). However, when either of the oscillator options are fed to the analyser (standard oscillator, B1 or B3) there is a 50Hz spike on the FFT (it goes from below -150dBV to around -120dBV). I shorted the I/P and flipped between analogue IN / gen 1 / gen 2 - and you can see the 50Hz is not there with shorted I/P and only present when loopback (or XLR leads from I/O) are used. Our other UPVs offer -113 THD+N with 2VRMS, but the serviced one only has -111 THD+N. If I feed it from another oscillator, it's cool, so the issue is isolated to the UPV output section.
My feeling is that a shield isn't grounded or a screw has been left out - that kind of thing. I am loathe to open the thing as it has a 1-yr guarantee. I am wondering if R+S will give us special dispensation to open it, assuming that there is an obvious instruction to fix it (hence my post here, to ask if anyone has taken one apart and can think of an obvious culprit?). It would be a bummer if we have to send it back to Germany just because someone left out an insulating washer...
They swapped the entire analogue board during the repair - repair report here:
The irony is that one of our UPVs was constructed out of a pair of totally broken UPVs (by us) that we bought for parts - and it has no 50Hz to worry about! We had front panel and keypad changed on the problem one, so it looks and feels like new....aarghh...
Any tips appreciated!
Update: it went back to R+S in Germany, who promptly sent it back to us, claiming that - despite being 2dB higher in terms of THD+N than either of our other UPVs - it's ok.
When measuring THD alone on loopback, you can see that the B1 lowers overall THD by around 6dB (as it should). However, in loopback, when measuring combined THD+N, the B1 makes hardly any difference at all when switched in.
I heard from a friend who's got about 10 UPVs that the original designer is no longer at the company. They 'shot-gun' repaired ours, by fitting a new analogue board (must've cost a packet - if you've seen the amount of parts on the board and felt its general weight) and doing no board-level fault-finding at all. My suspicion is that they either can't be bothered to find why the noise spec is higher than it should be, or they don't have the expertise left at the company. Maybe it's a combination of the two? They no longer make AAs. I doubt they care less. We need to get a general purpose spectrum analyser for PSU testing / EMC, and will be looking at other OEMs. The UPV is fine for all of our work as it is, as we're not in the DAC arms race. But to see the THD+N value remain virtually the same when flipping in the B1 is unacceptable. Once it's out of guarantee, I might try flipping a PSU out of another UPV and seeing if that's what it is. Be aware if you need service from R+S. If you're not spending 6 figures, they probably aren't bothered about your custom.
When measuring THD alone on loopback, you can see that the B1 lowers overall THD by around 6dB (as it should). However, in loopback, when measuring combined THD+N, the B1 makes hardly any difference at all when switched in.
I heard from a friend who's got about 10 UPVs that the original designer is no longer at the company. They 'shot-gun' repaired ours, by fitting a new analogue board (must've cost a packet - if you've seen the amount of parts on the board and felt its general weight) and doing no board-level fault-finding at all. My suspicion is that they either can't be bothered to find why the noise spec is higher than it should be, or they don't have the expertise left at the company. Maybe it's a combination of the two? They no longer make AAs. I doubt they care less. We need to get a general purpose spectrum analyser for PSU testing / EMC, and will be looking at other OEMs. The UPV is fine for all of our work as it is, as we're not in the DAC arms race. But to see the THD+N value remain virtually the same when flipping in the B1 is unacceptable. Once it's out of guarantee, I might try flipping a PSU out of another UPV and seeing if that's what it is. Be aware if you need service from R+S. If you're not spending 6 figures, they probably aren't bothered about your custom.