Electronics > Repair
E4407B Tracking Generator Repair
smgvbest:
Here's the PICs of control board for the BITG
smgvbest:
and last two
analogRF:
there doesn't seem to be any RF switches or electronic attenuators at first glance. I may have missed something though...but clearly you have several Minicircuits MCL29 gain blocks and HMC311 Hittite/analog device/ gain blocks and I would suspect them. You can start by checking their supply voltages based on their datasheets. if you can make an extension ribbon cable and bring the board out then it would be fairly easy to probe even with a home made 500Ohm RF probe and a spectrum analyzer or power meter at least.
smgvbest:
--- Quote from: analogRF on September 24, 2020, 03:23:06 pm ---maybe I missed something but why dont you just simply start by checking the levels at the major LO connections? I mean the LO in/out levels at the control board and the LO in at the TG module (which is the same as LO out from control board)? just vary the center frequency at zero span
and vary the TG amplitude and monitor the LO levels at these 2 points (one at a time) it should be fairly easy to rule out one of the modules
since the error occurs at some intervals , it seems to me the problem could be either an electronic attenuator somewhere OR an electronic RF switch which changes the signal path depending on the level requested (more likely in my opinion). I think I saw a couple of them in one of the pictures. I need to look again. But the circuits are very simple and easy to diagnose. there is no need for schematics
--- End quote ---
Hi,
So a few thing on that. the only SA I have that can look at the LO is the E4407B. when you enable the TG it turns on the LO to the TG and your range is reduced to 0-3Ghz. if you go outside the 3Ghz range which you need to for the LO (starts around 3.9 Ghz if I recall) the TG LO is turned out so you can't view it on the SA itself.
Second item is there are 2 errors associated with the TG
Source LO Unlevel (whcih I am not getting) and points to the LO being a problem on the Control Board.
Source Unlevel (which I am getting) points to a problem on the A2A2 (BITG) board.
I've disconnected and terminate the LO coming from the control board and still get same errors.
The only reason to check those FETS and PIN diodes was because at least a few of the FETS had been replaced and that's me doing my due diligence it looking at them
the good thing with the BITG is it sits high enough that if I leave the shield off I can likely probe the board.
I've spent most my time right now documenting these board as there's nothing out there on the TG.
Now that I have its time for troubleshooting.
I welcome any advice I can get here. RF is not my specialty by any means. I think I see the signalpath (not trying to steal their name or anything) so there's not many places I can see it could go bad on the BITG
analogRF:
some thoughts...
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