Re: HP-8753E S11 Intermittent Results - Switch or Bridge?
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Yes, I plan on maintaining what I can. I have fixed a few issues with the other CPU Board (now my spare), with the GPIB Interface. I am trying to get my hands on enough spares to keep on hand. It is clear from the service manual, none of this was meant to be troubleshot in the field. I also need to get my hands on some extender boards too. I have been looking at the HP-438A, and appropriate sensor. I see people have gotten good deals on the 438's too. Not to mention, my Millivac (made by Boonton) is getting a bit long in the tooth, but its very useful for some of the low frequency work I do.? Rich I was actually looking at a 438A with the appropriate sensors.?
On Sunday, March 6, 2022, 11:51:54 AM EST, Lothar baier <lothar@...> wrote:
If you plan on using and maintaining your 8753 than I strongly recommend for you to get you a powermeter and sensor , 4418A/B (E441A)? have gotten fairly cheap ($200-300 but sometimes you can catch one with best offer for less )? or you can buy a 437B cheap ,? as well as a 8482A , if you have a option 006 unit a 8481A . You need those to run the source as well as sampler correction tests/adjustments if you ever repair anything ,? you also need a GPIB cable to connect it to the VNA ? Sent from for Windows ? From: Rich Miller via groups.io
Sent: Sunday, March 6, 2022 10:11 AM To: [email protected]; [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP-8753E S11 Intermittent Results - Switch or Bridge? ? Lothar: ? That was a good warning!? Yes my A5 Sampler is a part number 5087-7001. My donor unit only has P/N 5087-7000. The donor unit was an OPT11, which may explain the difference in Samplers. I would not have caught that one right away!
? On Sunday, March 6, 2022, 11:04:59 AM EST, Lothar baier <lothar@...> wrote: ? ? A few comments on this , I have hardly ever seen any issues with the signal processing past the sampler , as far as changing the sampler keep in mind that the R and A,B channels use a different part number so pay attention ,? also I want to point out that changing the sampler will require you to run the sampler adjustment tests ? Sent from for Windows ? From:
Rich Miller via groups.io ? I checked all the cables around A5 which is the Sampler attached to Port 1. These all look good physically. I am unable to change the response by moving them or shaking them. Next, I will remove the A5 Sampler and replace it. After looking at block diagram provided in the service manual (not great for troubleshooting), I will not attempt the removal/replacement of the A11 board. It seems to me, that if there was a problem beyond the sampler, I would expect to see an alarming result on Port 2 if the A11 board were bad. If I am wrong on this, please advise.? ? Rich ? On Sunday, March 6, 2022, 12:23:46 AM EST, n8zmTWH@... <n8zmtwh@...> wrote: ? ? I think you can just move the cables that connect the couplers to the samplers without having to move hardware around. ? From: [email protected]
<[email protected]> On Behalf Of Rich Miller via groups.io ? I think I confused everyone, sorry!? ? What I have done now is swapped both couplers. The problem stays does not follow. It is something in the Port 1 line beyond the coupler. I do have extra samplers here, I suppose no harm in trying it.? ? I should note, I am now seeing these wild results below 3GHz, but nowhere as bad as I see it above 3GHz. 4 - 5 GHz is where it's most consistently bad. ? Let me take a look at the service manual, and determine which sampler I need to swap. Would be nice if that were the issue! ? Rich?? ? On Saturday, March 5, 2022, 11:34:04 PM EST, n8zmTWH@... <n8zmtwh@...> wrote: ? ? Agreed, but does the switch ¡®know¡¯ about the band change? That¡¯s what is curious here. ? ¸é¾±³¦³ó¡You said that the problem follows. Do you mean that the problem still occurs with the port 2 coupler? So it did not follow the coupler, but remained on the port 1 side. ? I wonder if it is a sampler problem instead. Maybe a bad cable from the coupler to the sampler, or from the sampler to the A/D? ? There is also a clue in that it stays OK when first turned on, until it is actually switched. ?
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On Behalf Of Lothar baier ? You are correct about the source switching above 3GHz BUT nothing changes at the source if you switch between S11 and S22 , if you have a source issue than its almost always symmetrical which means it appears on S11 and S22 . The Switch is a solid state switch that is a cascade of multiple cells to increase isolation , each branch has ESD protection diodes which are supposed to protect the switch cells from ESD if those diodes get damaged the effects appear most significant at higher frequencies than at lower ones first S11 and/or S22 of the switch also degrades which affects the source operation asymmetrical ! ? Sent from for Windows ?
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n8zmTWH via groups.io ? ¸é¾±³¦³ó¡ ? From your picture, the problem is above 3 GHz. The Source oscillator does a major band switch at about 3 GHz, which suggests that might be where the problem is. The SS switch ¡®could¡¯ be erratic, but it just doesn¡¯t seem likely, especially since you are not seeing any power level changes. ? When you power up and just let it run for a while without changing anything, does it stay good? ? If you put a through between ports 1 and 2, and look at S21and S12, what happens? ? Also, does S22 behave properly? From your original post, I believe it must be OK, but I¡¯m double checking that conclusion. ? One caution about cables. They can build up static charge between the center and outer, which dumps into the ports when? connected. Usually only a concern with long cables, but¡ ?
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On Behalf Of Rich Miller via groups.io ? I just got done measuring the power out at Port 1. To my surprise, I cannot detect any significant power output fulgurations. I have tried 3GHz, 3.707GHz (worse offender in S11 Response), 4GHz and 5GHz.? They all look very stable, when switching back and forth. I am using a power meter which is not rated for accuracy at 3 - 6 GHz, but I can set the output to 0dBm look at the measurement, and switch back and forth and look for any relative change. It is not fluctuating whatsoever.? ? I also checked 3GHz with my MDO, and that is a accurate power measurement. Now I am scratching my head again.
? On Saturday, March 5, 2022, 07:16:43 PM EST, Lothar baier <lothar@...> wrote: ? ? Try to find a cheap working 85047A ,? it uses the same inerts as the 8753D/E/ES including the solid state switch and you get 2 couplers as added bonus . ? Take one word of caution though ,? when handling the switch use a ESD mat and wriststrap or at least put some esd caps or terminations on the SMA connectors ,? those suckers are really sensitive to ESD ? Sent from for Windows ?
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on behalf of Rich Miller via groups.io <av8torrich@...> ? Yes, I am leaning this way (switch being the issue). I think it could also be that I was running a bunch of two port calibrations using a Agilent 85093 this morning (testing eCal out). I had some averaging on, 1601 Points, and 300KHz of IF B/W Set. Needless to say there was a lot of switching going on today. Let me check the power output now, and then flip it over and pray that one of the connectors on the switch is loose. ? Looks like the parts hunt is likely on! ? Rich ? On Saturday, March 5, 2022, 06:55:27 PM EST, Lothar baier <lothar@...> wrote: ? ? The reversing switches are notorious for failures especially if a unit is used in a environment that is not ESD protected .? what you can also do and you have to be cautious if you do this is to remove the switch , remove the hardline from the switch to coupler port 1 and connect the coupler directly to the source , if your trace is consistent then you definatly have a bad switch ! ? ? Sent from for Windows ?
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Rich Miller via groups.io ? Hi Lothar: ? It just started failing Port 1 Test. I was doing this just as this email came in. It is failing it consistently. I do not have a power meter, but I can take a look with my Spectrum Analyzer to see if there are power fluctuations at 3GHz. This problem seems to focus at frequencies higher than 3GHz.? ? Once I have a look at the output power, I will open and have a look. This is a new problem, as I never saw this before. ? Rich ? On Saturday, March 5, 2022, 06:38:56 PM EST, Lothar baier <lothar@...> wrote: ? ? If the S11response changes when you switch back and forth than this would point towards a repeatability issue with the solid state switch the fact that this changes with temperature would also point towards this direction , so here are a few things to try : ?
? Sent from for Windows ?
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Rich Miller via groups.io ? All: ? ? I have an issue with S11 (Port 1). It showed it's head now that I am running two port calibrations, thus I have not detected it just yet. My hunch is I have a problem with the switch, but not the Bridge. Here is what I am observing: ? 1. Upon boot up I get a good/normal S11 RL Response into a good 50 Ohm Load. This Condition will persist until I do one of the steps below. ? 2. If I switch to Port 2 (i.e. S22 Measurement), and then back to Port 1 the S11 Response has gone nutty (See Attached Picture).? ? 3. I have noticed, that if I depress the S11 MEAS multiple times, the S11 RL Response returns to normal.? ? 4. If you look at the enclosed picture, I have captured what I refer to as a normal S11 response, which I saved to memory (Smooth), and what it looks like after pressing S11 again (Wild variations in response). ? I have noticed there is a stark difference between instrument, cold and warm on S11. I do not however see this behavior our of any of the Port 2 Measurements regardless of temperature. Is there anywhere else this could be coming from other than the Solid State Switch, or am I way off base in my thinking here?? ? ? Rich? ? ?
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