| Electronics > Repair |
| CMU200 Rx level issue / failed loop test |
| << < (14/15) > >> |
| DavidAzulay5000:
Today I checked all frequencies between 1200 and 2200 MHz are bad Example with I fed from RF3 frequency generator In the example -20DB The signal is low -50DB Up to frequency 1200 and above frequency 2210 The device works perfectly I don't have another spectrum analyzer for this moment i give up |O When I ordered the filters I ordered 3 types the 836.5MHZ B122 and 2 types of 1842.5MHZ the [50pcs] B69813-N1847-X475 PCN RX Filter 1842MHz SMD It was really rubbish installed was no signal at all frequencies that I installed the B39182-B4139-U410 1842.5MHz SAW Filter 50 Ohm SMD All frequencies up to 1200 and above 2200 were perfectly fine again. With the new filter of 1842.5 The Internal loop test range of 10 MHz and 1200MHz perfect range of 2205-2700MHz perfect succeeded Better than the original. The frequency group 1200 to 2200 is really bad the fm modulation calibration pass But still failed L1 CO PRO LEVEL CAL The level is too low. Check the if signal connection |
| _Wim_:
--- Quote from: DavidAzulay5000 on February 16, 2023, 09:37:12 pm ---I don't have another spectrum analyzer for this moment i give up |O --- End quote --- As an alternative, you could just bridge the filter (IN directly connected to OUT). This will allow the spurs to pass also, but should give you a slightly too strong signal (original filter had a 3dB insertion loss, so I expect the signal to be +3db of what was expected). If the signal is still to low with a shorted filter, the issue is not the filter but somewhere else. The signal path is relatively easy to follow on these boards (see also my post https://www.eevblog.com/forum/repair/cmu200-rx-level-issue-failed-loop-test/msg3916070/#msg3916070), so than it is a matter to track down where the signal stops (but this does require a way of measuring an RF signal, like a spectrum analyzer or RF-power meter) |
| Andrejka:
Hello, Sorry for offtopic. Maybe someone have additional 1842.5 MHz filters to sell? Thanks Andrej |
| st0ne:
Hi all :) i fixed my CMU200 by cleaning the filters and covering them with conductive paint which is used for repairing keyboard traces! Maybe this information is helpful :) https://www.amazon.de/gp/product/B07WJTYXPH/ this conductive paint is very fluid and gets hard with a hot air gun and about 100C temperature. all tests passed :) Philipp |
| _Wim_:
--- Quote from: st0ne on July 25, 2024, 05:59:44 am ---Hi all :) i fixed my CMU200 by cleaning the filters and covering them with conductive paint which is used for repairing keyboard traces! Maybe this information is helpful :) https://www.amazon.de/gp/product/B07WJTYXPH/ this conductive paint is very fluid and gets hard with a hot air gun and about 100C temperature. all tests passed :) Philipp --- End quote --- That seems like a very good way to fix this. Much easier than locating the required parts. Thanks for posting! |
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