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| Agilent 8753ES A24 Microwave transfer switch substitute |
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| inaxeon:
I have another question too... How come this thing has so many large tantalums on it? |
| inaxeon:
The original repair option I was thinking of a custom PCB with some off the shelf switches like the one attached (I had mostly designed it before starting this post) I'm using two HMC1118's back to back, which should get 100 dB isolation. Frequency range and insertion loss look to be OK for this too. RF resistors for the termination (whatever I can get my hands on, very little at the present time) and a fair bit of care taken to provide clean supply / control too. I know this will impair the instrument, but I'm just a hobbyist here. So long as I can make some approximate measurements with it and not stress over a $1000 bill if I have an accident that would be brilliant. |
| Joel_Dunsmore:
The back to back switch might work. I found parasitic ground inductance really wreaks havoc with isolation on the switches; as well as radiation leakage. I'd be curious how it turns out. I started with such a structure and could only get about 60 dB isolation at 6 GHz, but of course entirely different switches in 1986. But you might also try tor repair your switch. It will either be the GaAs IC switch that went bad or the protection diode. If it is the protection diode you can just reach in with a tweezers and pluck it off. I outline in blue the protection diode. now that I see inside, I recognize that's a redesign of the PC board with new SMT parts which happened when something on the through-hole board went obsolete; done by our production engineering team. The Tantalum capacitors are needed to bypass all the control lines (6 of them) plus the voltage inverter (I think that's the LT1054). We need a lot of bypassing to keep 100 dB isolation at 10 kHz. Oh, I should say you can test it without the lid just to see if it is working after plucking the protection diode. When you go to put the lid back on, take the grey conductive rubber bits off the base and stick them back in the lid first. |
| inaxeon:
I am going to try repair the one I have. When I get a chance I'll pluck that diode and see what happens... |
| inaxeon:
While I have you on the line, would you be able to identify the numbered components for me? I'm just interested to know... |
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