Re: HP Agilent 8753ES VNA repair [Help]
开云体育Hi, ? This means that one of the PLLs does not have the right frequency. The frequency near 22.5kHz will not pass through the filters which are for 4kHz at the DIGITAL IF. ? You should check the second LO, it arrives through the motherboard, not easy to access. Connect a test wire as in the picture to measure the output of the second LO on A12 PCB. ? For a frequency below 16MHz, the frequency will be CW FREQ+4kHz, for example, for 100kHz output Port#1, you will have 104kHz. For frequencies of 16MHz and above, you will have 996kHz. ? Yves ? ? De?: [email protected] <[email protected]> De la part de MattSNE via groups.io ? Hello Yves, ? Thank you for your screenshoot. Here is what I got on my board. ? TP20 B (with look cable between port 1 and port 2):? ? ? TP18 A (OPEN loop between port 1 and port 2): ? ? TP16 R: ? ? I check the TP1 5V and the voltage is OK here.? ? Two points here : - I had to put the probe level in x2 mode in my scope to measure the same voltage than you in peak to peak mode. The voltage I measure initially was divided by two. I don't think this is important.? ? ? |