| Electronics > Repair |
| Anritsu MS2651A repair (need service manual) |
| << < (9/12) > >> |
| jimon:
khach, woah thanks, first time see mixer like that! =) |
| jimon:
Ok, I've finally found where the IF out from RF module! This is LND11 port visible from one side of a module. This output is barely amplified (there a pot on other side), noise level is around 50 mVpp, and 0dbm is around 120 mVpp. |
| jkf1000:
It looks like our RF boards are pretty much identical but there is a difference in part numbers so not sure what if anything may be different in the operation. Mine is a Anritsu A1001 322U12943b (Y2) Just measured mine from the same LND11 point and this is the wave form that I got on a single shot capture. It was a real pain to get it to trigger as there seems to be a lot of noise and other signals at that point. I have the trigger set just at the top of one of the peaks. If I just let the scope run the signals on screen are very messy. I am still waiting for the video chip for mine which should be here in the next few days so have not really done anything with it, but it is still open on the bench if you need measurements. Karl |
| jkf1000:
My video chip finally arrived (HD63484CP8) but unfortunately made no difference, still no HSYNC/VSYNC control signals so still no display. It looks as if either the information being sent to the chip is being corrupted by a peripheral chip or the CPU itself is not generating the correct data to be sent to the video chip in the first place. I have done a lot of measuring with the scope and DMM and found several ICs on and in the path of the video chip so not sure which direction to go next. I am thinking of starting a seperate thread just for help on the display problem as I am now out of my comfort zone as far as diagnosing further on the digital signals.. Karl |
| jimon:
Got some time to tinker with that big boy, so I learned how to tune and measure : second LO, IF, and now I'm getting 118.7 MHz there! Apparently first LO was 100 MHz off and is not locking correctly, if I set CF to 200 MHz and than go to 0 Hz with 20-50 MHz increments - it works. If I set to CF to 1-3GHz and than suddenly jumps to 0 Hz - YTO locks (? not sure if it locks at all) around 50 MHz off ... which kinda explain random crap I observed and why DC was off by ~40-90 MHz. Thanks my stupid brain was smart enough not to touch cavity filter screws because I don't have tools to calibrate that at all. Now I need to understand how the heck YTO PLL is working there, and where the hell are lock signals if any. MS2601 supposedly have LEDs to represent this, and looks like MS2651 have none. |
| Navigation |
| Message Index |
| Next page |
| Previous page |