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HP 8595E SYTF 5086-7803 PIN switch problem
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I've got a 8595E which works perfectly fine in the high band but it's about 24-26dB down (almost flat) in the low band (9K-2.9G)
Long story short, by doing various measurement, I have confirmed that the PIN diode switch inside the SYTF when switches to the low band is dead (exactly 24-26dB loss over the band) so it does not pass the signal through to the mixer everything after the SYTF works fine when I directly inject low band signal. The YIG filter itself is of course fine, too. It seems to me that the PIN diode in the shunt arm of the switch is shorted perhaps due to excessive input power. It also overloads the switch voltage that comes from A7 board, instead of -9.8V it becomes -3.6V when that switch is supposed to close. But for eh other pole of the switch (high band) it is -9.8V as it should Anyways, since I have never opened a SYTF or any YIG tuned stuff before I have a couple of questions I was hoping someone on this forum can help me with: 1-what are my chances of repairing the switch and not messing up the YTF? 2-Are the switch and the YTF in two separate compartments? If I attempt to open it up is there anything that might fall off and mess the whole thing up? 3-is the switch made of wire bonded microcircuit elements? I don't have access to any wire bonding stuff. Only my soldering iron! thanks |
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...Another solution that I am considering is to buy a microwave SPDT switch (even SPST can do)
and put it between the attenuator and the input of YTF. For the high band the switch will pass the signal to the SYTF and it does its job perfectly but for the low band the switch will divert the signal (pass through) directly to the dual mixer. The biggest issues are generating compatible switching and power supply voltages from what is already on the A7 board for that I will have to put is some transistors and stuff somewhere! and the next issue is where to mount the switch in the RF compartment. There are some small spaces here and there and maybe I can squeeze it somewhere... However, the type of the switch is critical. First I was looking at relay switches for example from Teledyne which have extremely good specs and relatively cheap but then it struck me that the switching times must be very small compared to the sweep speeds of the SA Relay switches are rated at 5ms-15ms switching times. The might work OK for most of the time but if it happens that your frequency span covers the transition between low band and high band and the sweep time is in the range of 10's of ms then it becomes a mess...that's exactly why? the HP designers only used PIN switches in all places in the RF section. Modern analyzers use GaAs FET switches. The switching times for PIN diode switches is? around 5-20nsec but of ocurse the can never achieve the insertion loss and isolation specs of relay switches. not even close.. Now the only thing I have been able to find was Minicircuits ZYSW-2-50DR and ZYSWA-2-50DR with reasonable specs up to 3GHz and even applicable up to 5GHz but not to 6.5GHz as I need. Any suggestion about a PIN diode RF switch that I can buy at reasonable price is welcome? |
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Hi First, the diodes will be small bonded ones, either beam lead or wire bonded. I have not opened one of these, but I have looked in one that also contains the high band mixer, so I'm pretty sure it will be in the same compartment as the yig, and things will be very small with wire bonding's around. You don't want to use a mechanical relay for several reasons, switching time as you noted, life span will be short when it has to switch every sweep, and you don't want to listen to the relay constantly switching. I don't have any advise for a switch you can use, but maybe someone else here knows of one. BR, Askild On Sun, Feb 3, 2019 at 8:31 PM amirb <amir.borji@...> wrote: ...Another solution that I am considering is to buy a microwave SPDT switch (even SPST can do) |
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Contact Louis, he can almost certainly repair it.
/g/HP-Agilent-Keysight-equipment/topic/new_group_on_chip_and/24781695?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,40,24781695 Vladan |
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I have also used National Test Equipment for some microcircuit repairs. I believe that when HP consolidated u-circuit manufacturing, then laid off that work force, quite a few of those folk got hired by National. They probably bought some of the fab equipment too. You should request a quote with your description of the fail mode. If we check we could post a list of their component repair capabilities.
Don Bitters |
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