Electronics > Repair
E4407B Tracking Generator Repair
analogRF:
--- Quote from: smgvbest on October 01, 2020, 03:29:11 am ---
--- Quote from: analogRF on October 01, 2020, 03:26:15 am ---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.
--- End quote ---
when I say no DC/BIAS I mean there is no DC of any kind at the input to IGG5.
--- End quote ---
at its RF input you mean?
how many pins does it have? cannot be just an input and output!
smgvbest:
--- Quote from: analogRF on October 01, 2020, 03:31:54 am ---
--- Quote from: smgvbest on October 01, 2020, 03:29:11 am ---
--- Quote from: analogRF on October 01, 2020, 03:26:15 am ---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.
--- End quote ---
when I say no DC/BIAS I mean there is no DC of any kind at the input to IGG5.
--- End quote ---
at its RF input you mean?
how many pins does it have? cannot be just an input and output!
--- End quote ---
yes at RF in
12 pins total. 3 on each side. RFin, RFout, all others go to ground.
Could the part the arrow points to be the detector?
suj:
--- Quote from: smgvbest on October 01, 2020, 03:47:30 am ---...
Could the part the arrow points to be the detector?
--- End quote ---
You may be right. Input resistive divider, filter capacitors and signal to AD620. On the second input of AD620, setpoint . The error signal at the AD620 output (in the sense of the difference between the actual value and the setpoint) being the ALC signal. You need to check the DC levels at the AD620 inputs and output at different RF signal levels.
analogRF:
--- Quote from: smgvbest on October 01, 2020, 03:47:30 am ---
--- Quote from: analogRF on October 01, 2020, 03:31:54 am ---
--- Quote from: smgvbest on October 01, 2020, 03:29:11 am ---
--- Quote from: analogRF on October 01, 2020, 03:26:15 am ---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.
--- End quote ---
when I say no DC/BIAS I mean there is no DC of any kind at the input to IGG5.
--- End quote ---
at its RF input you mean?
how many pins does it have? cannot be just an input and output!
--- End quote ---
yes at RF in
12 pins total. 3 on each side. RFin, RFout, all others go to ground.
Could the part the arrow points to be the detector?
--- End quote ---
obviously there is no DC anywhere in the RF path. there shouldn't be.
yes, it is. If IGG5 has no other pin than the RFin/RFout and GND then it is only functioning as RPP.
And by the looks of it, that circuit you pointed is indeed the peak detector (that must be a schottky diode)
this makes it easier to probe in and also to repair if the problem is in this part.
you need to find out why at -10dBm setting and -2dBm setting the ALC_MON signal is so different
because the TG must have the same -2dBm output amplitude in both cases.
smgvbest:
--- Quote from: analogRF on October 01, 2020, 02:22:25 am ---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!
--- End quote ---
Did this. the only component that had effect using cold spray was the HMC346 it only shifted it down (lower db reading) but unlevel condition continued
tried the other board on the TG (one with OPAMPS and Analog Switch) , no effect there either
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