| Electronics > Repair |
| Aeroflex IFR-2398 / calibration / repair help |
| << < (5/16) > >> |
| KJDS:
--- Quote from: andy_silicon on July 01, 2014, 06:13:42 pm ---I'm beginning to suspect a bodge on the input to the 1st mixer. There is space for a single smd ( probably an R ). However three components have been soldered to the board in an hf boost filter. ( R in parallel with C and this combination in series with an R ) If the C has gone bad , it might explain the reduced gain and overall HF fall off. ( about 30-40dB down at 2.7G compared to 40Mhz ) --- End quote --- What value is the R? It would need to be huge to cause a big drop in gain. |
| andy_silicon:
At the moment I can't easily see ( it's a vertical stack ). I'd rather be sure before disassembling it - so will check some other things first. What does concern me a little is that the mixers are supposed to be +7dBm mixers - and I don't see that level at the LO . More digging. At the moment I'm only sure it's between the 1st and 3rd mixer ::) |
| andy_silicon:
I think there is at least a problem with the 1st amplifier ( after the pre-amp) It's supposed to have a gain of 16dB , I'm only seeing 10dB It's a white 4 pin blob marked 101. Frequency 3.4ghz , 60mA 4V I can't find the part number as yet. Also - I can get the unit to pass the level cal by using the factory menu and setting the value for the expected cal signal level. So - that would at least seem to indicate the reason for the level cal is purely the gain problem. I think I've also located the undocumented gpib commands for reading and writing the receiver level correction tables. There is a correction every 10Mhz from 10Mhz to 2750Mhz. |
| andy_silicon:
Nearest part I can find is an Agilent ATF-10136 Looks the same - but the gain is potentially a couple of dB lower. Hmmm. |
| KJDS:
--- Quote from: andy_silicon on July 02, 2014, 06:10:43 pm ---Nearest part I can find is an Agilent ATF-10136 Looks the same - but the gain is potentially a couple of dB lower. Hmmm. --- End quote --- That gain is specified when matched for optimum noise figure. I suspect that it will be higher matched for best return loss. |
| Navigation |
| Message Index |
| Next page |
| Previous page |