Hi Alex,

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Based on my experience with the 4401B, there could be a number of causes:

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* Blown front end

* Faulty 50 MHz internal test signal

* Bad mixers or

* IF issues

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You really can’t tell from just the error message.? The service manual will help you identify which major component/board is the likely cause.? Once you have that, you will need the CLIP to determine the problem in that component.? To trace down the issue in the signal path, you will need active RF probes as Amir has mentioned, and test equipment capable of measuring the 1^st and 2^nd IF stages.? This is where I am currently stalled on my 4401B, while I wait for more capable equipment to arrive.

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Depending on the price of the unit, and your needs, it could be an interesting learning experience on RF probing and troubleshooting.? However, if you are looking to have a functional unit that you can start using soon, you should probably keep looking.

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Cheers,

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Mike

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Sorry to barge in with this, but I have my sights on a 4411B (I assume it is similar to the 4401B being discussed here) that has a message on the startup screen that says "Align RF Skipped, No align signal". Is it possible this is just being caused by some setting being wrong, or could it be a similar problem as discussed here?

I am new to these units and considering getting one (~cheap) for the barn.
Any insight into this appreciated.

Thanks.