| Products > Test Equipment |
| Looking for the serive manual of an HP 70951 optical spectrum analyzer |
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| nctnico:
I'd be carefull with saying those reed relays are OK. I had an HP function generator and after a while (with the internal temperature rising) the relays started to act up causing all kinds of weird behaviour. It took me quite a while to figure out the cause was in the relays because they tested just fine. |
| _Wim_:
--- Quote from: nctnico on June 24, 2023, 11:49:22 am ---I'd be carefull with saying those reed relays are OK. I had an HP function generator and after a while (with the internal temperature rising) the relays started to act up causing all kinds of weird behaviour. It took me quite a while to figure out the cause was in the relays because they tested just fine. --- End quote --- I agree that there could also be and inconsistency issue with them, but when I tested them (cycling each approx. 5 times) they worked flawlessly, and the issue the 70951 has is very consistent (does not change when just started up to hours later). I get only a signal on high sensitivity settings, and that signal can be partly blanked-out when "auto-ranging" is "on" (so when it tries to switch the gain in the middle of the sweep). This auto-ranging is presumably done with the solid state switches, although I still need to verify if that is the case. |
| _Wim_:
On lower sensitivity settings I get something that looks like this (so essentially equal to the blanked out section above, but then for the entire spectrum). So it really seems the unit is unhappy with "strong" signals, indicated it might have been severely overloaded in the past |
| zrq:
I'd be a bit surprised if it was an overload that caused the problem. The photodiode will likely die before the electronics. |
| nctnico:
Can you burn out an optical attenuator? I suppose there are some mechanically operated optical attenuators somewhere in the signal path. And with the device working for low level signals, it could be these are switched in / out of the path. I'd check whether these attenuators still work. |
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