| Electronics > Repair |
| CMU200 Rx level issue / failed loop test |
| << < (8/15) > >> |
| _Wim_:
--- Quote from: Michael-VK2BEA on January 19, 2022, 09:27:58 pm ---I didn't notice before but your layout is different than my RXTX board. In mine the 936 MHz filter is at the edge of the board. --- End quote --- Ach indeed, you board does look quite different. Something to watch out for when attempting this repair. It was already very tight on this layout, but luckaly it just fitted. |
| _Wim_:
Now that I look at the pictures again, I did also install the filter in reverse (output used as input). I presume these filters are fairly symmetrical, but should maybe check if no additional spurs are seen by doing it this way.... |
| Michael-VK2BEA:
--- Quote from: _Wim_ on January 19, 2022, 09:48:21 pm ---Now that I look at the pictures again, I did also install the filter in reverse (output used as input). I presume these filters are fairly symmetrical, but should maybe check if no additional spurs are seen by doing it this way.... --- End quote --- I think you are right ... they should be palindromic (50 ohms in and out, passive and linear). I'll see if I can confirm on the VNA. I think there should be a way to fab an intermediate board that gives a better ground (and lifting above the other components). BTW It seems R&S used these filters in other devices. I spotted them the other day in Shahriar's (Signal Path) repair video of the FSL spectrum analyzer. (see them here in the bottom left https://youtu.be/60hasxvl5KU?t=1044) |
| _Wim_:
--- Quote from: Michael-VK2BEA on January 20, 2022, 12:42:10 am ---I think you are right ... they should be palindromic (50 ohms in and out, passive and linear). I'll see if I can confirm on the VNA. --- End quote --- :-+ :-+ --- Quote from: Michael-VK2BEA on January 20, 2022, 12:42:10 am ---BTW It seems R&S used these filters in other devices. I spotted them the other day in Shahriar's (Signal Path) repair video of the FSL spectrum analyzer. (see them here in the bottom left https://youtu.be/60hasxvl5KU?t=1044) --- End quote --- Good find. Probably not a "cheap" donor though... :) |
| Sas:
--- Quote from: _Wim_ on January 19, 2022, 08:50:31 pm --- All tests past, even the FM Calibration that failed before! --- End quote --- Congratulations on the repair :-+. Can you do the 1-> 4 and 3-> 2 loop test with a positive result? --- Quote from: Michael-VK2BEA on January 20, 2022, 12:42:10 am ---BTW It seems R&S used these filters in other devices. I spotted them the other day in Shahriar's (Signal Path) repair video of the FSL spectrum analyzer. (see them here in the bottom left https://youtu.be/60hasxvl5KU?t=1044) --- End quote --- SA R&S FSH3 also has the same filters. I don't have MMIC amplifiers yet and work stopped. I got the same filters from the same seller. The interesting thing is, each of the filters is different, one of the filters has large offsets between the sections. The entire 3 pole BPF consists of three separate filters. |
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