Tracing it so far. It does not go directly to the RF side of the A2A2 board
Goes thru a analog switch which switches between a fet op amp and J3 which is not connected, then to Q1 which I haven’t been able to find yet. It’s a 6 pin can. See Attached
Tracing it so far. It does not go directly to the RF side of the A2A2 board
Goes thru a analog switch which switches between a fet op amp and J3 which is not connected, then to Q1 which I haven’t been able to find yet. It’s a 6 pin can. See Attached
Oye, I just did a SUT, I was not tracing TUNE on Pin5 I was tracing ALC_EXT on Pin10. I don't' know where I got Pin10 from but pretty much ignore my previous post. I'll go retrace Pin5 for Tune and see where it goes.
So when you trace the correct PIN its pretty easy to find.
See attached
(Attachment Link)
So not a exact replacement if this is what wrong. I found this the attached.
The pinout is very close, mainly NC pins on the side that do not appear on the device in the unit.
I will pull out the Rigol tomorrow and probe before and after that component with the TG set to zero span and 50Mhz. at -9dB i do not get the Source Unlevel, at -10dB I do. so the output will be well withing the range of the Rigol SA, I can also probe the 600Mhz in and the VCO. I will get that done soon with a poor mans rf probe.
this chip does not have any peak detector output for level control loop. the one in your TG does RPP and has level detector.
it's good strategy to probe before and after that IGG5 when the error appears and when it doesn't
also at that point I suggest checking the control voltage that goes to the HMC346 variable attenuator and see if it is changing or not
and also check the the PWR_LVL signal that comes from A2A1 to the connector pin 8 and also the ALC_MON at pin 6.
these are all DC so easy to probe and document what you see
1-what are these numbers? what does -57 mean?
2-what did you measure them with? I mean was it scope or a spectrum analyzer?
3-the most important thing is what probe did you use?
4-for VCO this is very strange! but we dont know what that pin is so please measure the VCO
at the RF input to the mixer (pin 3) and also more importantly measure the IF output
you can measure at pin 2 of mixer but better is to measure at the output of the big filter which is the input pin of the blue "LF3" filter
V1 = 0.181/-1.7
v2 = -4.191/-2.48
I = -0.585/-5.85
Everything is in dB on first photo
Measured with Rigol 1.5 ghz SA
scope probe. Still waiting on sma to make that diy probe you mentioned
Interested in relative values in this case. Should show if amps working
And IGG5 has same in/out
For VCO I measured with just a 50 ohm lead first. Then probe. Got same value except probe was lower dB
I’ll check areas you mention.
I did check the Bias on the MCL29 which read 3.57vDC and the MCL59 which was 4.7vDC
at the front panel connector. Normally (not necessarily) for anything above 0dBm there should be no attenuator switched in but for -10dBm there is perhaps a section switched in like 8dB for example then your BITG must produce -2dBm at output.
at the -10db it says the 8db attenuator is active.
I will have to trace the board to find the op amp the pwr_lvl goes to.
Sandra,
I have just started reading this topic.
Correct me if I have misunderstood one of your earlier posts, but I understand that you have the schematic drawings for the 3Ghz A2A1 Driver board but not for the 3Ghz A2A2 RF board.
I have a printed copy of the drawings for the 1.5Ghz version of the tracking generator A2A2 RF board which I may be able to try to have scanned if this will be of any use to you. (There are 13, A3 size sheets).
Regards.
Sandra,
I have just started reading this topic.
Correct me if I have misunderstood one of your earlier posts, but I understand that you have the schematic drawings for the 3Ghz A2A1 Driver board but not for the 3Ghz A2A2 RF board.
I have a printed copy of the drawings for the 1.5Ghz version of the tracking generator A2A2 RF board which I may be able to try to have scanned if this will be of any use to you. (There are 13, A3 size sheets).
Regards.
I have managed to scan these drawings. Some of the scans may not be very good as the printed copies are very feint.
There is a total of around 8Mb so I will split the files across a couple of posts.
Also included is a scan of the 1.5Ghz A2A1 Interconnect drawing for reference.
Hopefully they will be of some use.
Regards.
First lot of files.
HMC346
3dB unlevel, then -10dB reading level
all vDCCode: [Select]V1 = 0.181/-1.7
v2 = -4.191/-2.48
I = -0.585/-5.85
change the level setting from -10dBm to 3dBm, 1dBm at a time and at each step monitor these signals (all DC) : the ALC monitor that goes from TG to A2A1. The PWR LVL that comes from A2A1. and V1,V2 on HMC346
these numbers look pretty consistent with each other (except one thing that I will mention below) and i cannot see which part might be the main culprit. which part is failing that causes the ALC loop go into saturation. maybe someone else can draw a better conclusion
however here is my take and my recommendation
1-the PW_LVL signal coming from a DAC on A2A1 was supposed to be between 0 and -11V (says on the schematic) here it does not go below -9.7
it does not necessarily mean anything and it could have been designed that way because for example V1 should not go too much positive but still
it's worth to check if that circuit (PWR_LVL) is ok both on A2A1 and also on the TG board because that signal eventually generates V1 (so what is between V1 and PWR_LVL)
2-The only inconsistency that I see in your measurements and that may be the path to the root cause is that all numbers are and must be similar (very close) for -2dBm and -10dBm settings. Because the TG has to generate -2dBm for both cases. However there is ONE voltage which is very different between the two cases and that is the ALC_MON. In fact between -3dBm and -2dBm it suddenly jumps -1V which never occurs anywhere else. At -10dBm where TG must be generating -2dBm the ALC_MON correctly stands at about -0.17.
What happens to ALC_MON at -2dBm and above looks like the TG OFF state. Since I believe the ALC_MON is coming directly from the IGG5 hybrid (please confirm whether this is right or not) the issue may be the IGG5. Or maybe a supply voltage to IGG5 if it has one?
3-Your 5V rails looks a bit low. Is it clean? did you check it when the failure occurred?
4-since the failure moves to lower amplitude as time passes, it is probably affected by heat. Why dont you spray some freeze spray (aim very locally) at different components and see if the error goes away. starting with that IGG5!
basically IGG5 should not need any DC bias, it has a peak detector and should generate a DC proportional to the power level
and that voltage after some amplification and conditioning by opamps or transistors will become ALC_MON
w.r.t. supplies, I think only the 5V rail seems a little low. check for any ripple/noise specially when the error happens and also for current draw.