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| E4407B Tracking Generator Repair |
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| analogRF:
--- Quote from: smgvbest on September 28, 2020, 11:34:45 pm ---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. --- End quote --- good, so we know that at +3dBm the TG must output 3dBm (no attenuation after that) and at -10dBm the TG should output -2dBm (only 5dB jump) your numbers did jump but not by 5dB between the two cases. The control voltage for HMC346 clearly show the controller has gone into saturation in order to minimize the attenuation to retain the 3dBm output but has failed. HMC346 control voltages must always remain between 0 and -2.5V and the maximum tolerable range (before killing the chip) is +1V to -5V. So for +3dB the controller is driving the HMC346 very hard to lower its attenuation. In my opinion this is probably just a symptom and may not be the actual cause of the unlevel issue. For example, still IGG5 may wrongly report a low level and therefore the controller loop will drive the HMC346 into saturation because of that. But it also could be the source of problem, I mean maybe the DAC on A2A1 is giving out wrong voltage or the opamp circuits driving V1,V2 on HMC346 have problem. it would be useful to check the ALC monitoring signal that goes out from TG to A2A1 board in the two cases and some levels in between to see how it changes |
| seronday:
--- Quote from: seronday on September 27, 2020, 11:44:38 pm ---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. --- End quote --- 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. |
| seronday:
Second lot of files. |
| analogRF:
--- Quote from: seronday on September 29, 2020, 03:42:26 am --- --- Quote from: seronday on September 27, 2020, 11:44:38 pm ---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. --- End quote --- 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. --- End quote --- This one is a completely different beast. Has no resemblance to the 3GHz version. |
| analogRF:
--- Quote from: smgvbest on September 28, 2020, 11:12:04 pm ---HMC346 3dB unlevel, then -10dB reading level all vDC --- Code: ---V1 = 0.181/-1.7 v2 = -4.191/-2.48 I = -0.585/-5.85 --- End code --- --- End quote --- 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 |
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