Hi Marco,

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The diode Macom MA4E1338B1 would be OK, I had also found this equivalent.

There was also TPM2840-03, a little bit more performing than the original diode, but really very close...only 5V protection however.

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I found a picture showing the section about the first converter of the 8591E which is different from the 8591A.

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The method I used:

• I replaced cr1 and cr2
• I close the lid and I test, I see if the signal to the monitor at 0Hz, is lower than ideally, at the first division (upper left, picture 8591 LO leakage).
• If the diodes are not matched well enough, the carrier at 0Hz will exceed the first division at the top of the left screen.
• In such a case, change CR2 only, because easier to replace and redo the test.
• It may work from the first attempt as in my case, but I had still tried a second attempt out of curiosity, and got slightly better, so I did not continue with further attempts.
• I successfully closed, tested and calibrated everything because there was no other problem.

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I will do some tests with the screen capture program controlling the rs-232 port.

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Yves

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