Hi all,
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I recently acquired another 8753D unit for parts. It turned out that the YTO is completely dead.
I've followed the source check flow chart including verifying the YO Coil Drive waveforms with Analog Bus and oscilloscope.
I've also hooked up the 5086-7934 module directly to 5V, 15V and coil current, no output at all. The 3.8GHz LO works as expected.
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After finding lots of useful info, mainly in this groups archive I see the following repair options:
- See if Luis Cupido - CT1DMK still repairs these.
- Buy an expensive A3 or 5086-7934 from eBay
- Adapt another YIG oscillator
- Create VCO synth replacement
So let's evaluate the options:
- Messages in this groups says he is out of FET transistor replacements to be able to do this repair but it would not hurt to ask anyway.
- Always a gamble and for how long will it work if it works?
- I happen to have a Wiltron YIG oscillator that works across the frequency range but its main coil drive consumes more power: 123mA 2.5GHz and 345ma for 7GHz compared to 70mA-160mA. The FM coil also works on the Wiltron YIG oscillator. One could build an adapter board but some more analysis needs to be done. For instance will the current MC and FM drivers handle the increased power usage or does that also need adaptation. -5V supply to the Wiltron YIG is another but -15V is available. Supplying 24V to the Wiltron heater is one more thing to handle, but could probably be ignored to start with. My epxerience with YIGs is that the heater just runs for a few minutes after power up.
- Seems there are attempts from various semiconductor manufactures to do this. for instance. The problem as I see it how to adapt the FM coil control to ensure phase noise stability.
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Comments about the options? Or any other suggestions?
I'm leaning to start trying option 3 or maybe option 4.
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Best regards
Marcus, SA5PMG
