Hi Jinxie,

If 0dB attenuation was damaged because of over voltage it would have damaged a lot more. It is very likely some mechanical problem like sticky o-rings. Your phase detector repair was a lot more complex, why don't you try repairing the attenuator first? Worst case is you need a new one so nothing to lose. It may be obvious but I will mention it: Once attenuator is out can test it with a DVM by terminating to 50-ohms at DVM and applying DC voltage. Just do 20*log(Vo/Vi). This attenuator doesn't have a DC block in it so DC would work.?

Ozan

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On Fri, Sep 6, 2024 at 10:14 AM, Jinxie wrote:

Hi Vladan,

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Many thanks indeed for your observations. I was certainly aware that the Analyzer would no longer 'know' what level of attenuation was being applied to the source RF and that I would have to manually account for it, but provided that doesn't put any of the downstream circuitry at risk of damage, it's an inconvenience I may have no alternative but to live with.

This SA was owned by an RF engineer and I purchase it from him about 10 years ago along with a faulty Marconi/Aeroflex RF signal generator with a disclosed fault. No faults were disclosed in regards to the SA, however. The sig gen I was able to repair and it's a valuable item of equipment to have for all sorts of reasons. Anyway the fact that the seller disclosed the sig gen fault leads me to believe he was honest and was unaware of any issue with the SA. However, I've never done anything with that SA which could burn out the 0 and 10dB settings either, having used it solely for monitoring the RF environment around me using a short telescopic antenna, so no physical connection to the RF input.

As I mentioned, I do have an HP 8495K 0-70dB attenuator which might save the day. I don't think there are any issues with that. However, it's NOT the same type as the one in the 8566B...