| Electronics > Repair |
| JDSU JD745A / GC747a Base Station Analyzer - Repair log |
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| Alenoiz84:
hi, I have a gc7105b that gets stuck in the boot screen with the gencomm logo. maybe the firmware is corrupt. I tried to search the network for the recovery file but I did not find anything. where did you manage to find it? |
| Qw3rtzuiop:
--- Quote from: Alenoiz84 on May 07, 2021, 05:27:39 am ---where did you manage to find it? --- End quote --- Here: https://updatemyunit.net |
| suj:
New JD745A owner here. Mine has a problem with the signal level in the spectrum analyzer and internal power meter (which uses spectrum analyzer hardware). The decrease in the indicated signal level is +/- inversely proportional to the frequency. At 3..4 GHz the indications are correct, at 1 GHz it is about -4 dB and at 100 kHz it is over - 20 dB. This may indicate a problem with coupling capacitor or one of the input ICs. I want to check the input capacitor and next element (3 dB attenuator?) by feeding the signal from the generator to the input and testing with another spectrum analyzer with the HP85024A probe. I have a problem with removing the mixer module from the case. Where is it still screwed on? Is there a screw under the sticker? The photo shows the state in which I stopped. |
| Qw3rtzuiop:
--- Quote from: suj on May 14, 2021, 10:27:27 pm ---Where is it still screwed on? Is there a screw under the sticker? The photo shows the state in which I stopped. --- End quote --- I marked the srews that hold down the module. There arent any srews under the sticker afair. |
| suj:
>I marked the srews that hold down the module... Thank you, I thought these screws were for these peripheral modules. My measurements of the input elements (coupling capacitor, attenuator or equalizer, diode limiter) did not show such deviations as I have noticed before. After putting it back together, the spectrum analyzer turned out to be correct in the 600 kHz to 4 GHz range. I'm not sure but maybe it was some PCB stress or problem with the N/SMA connector at the input of the spectrum analyzer? At the moment, this range of correct indications satisfies me, and I will check whether it is a permanent solution from time to time. Alternatively, I will check whether the range below 600 kHz will be possible to correct in the calibration files. BTW. I weighed the screws used to tighten the PCB screen of the mixers. It's good that I used an electric screwdriver to unscrew and screw it back together. :phew: |
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