Re: HP Agilent 8753ES VNA repair [Help]
Sorry for delay, ? For high band VCO must be 39.84Mz and VCO at 39.996MHz for lowband <16MHz. Divider: 4kHz for low frequency and 160kHz for high frequency. ? VCXO 40 MHz, your SPAN of Spectrum is to wide, use narrow span to see more detail, VCXO but is working. Test VCXO with input generator 10 MHz with a step of 100Hz…measure at TP VCXO, see picture below test VCXO. Divider to 160kHZ works but bad frequency. For CW 10MHZ, LO2 TP14 will be 10.4MHz…for low frequency it’s OK. No DC correction for PLL of VCO…defective phase comparator, integrator or mixer…and 21V is very high voltage. ? 
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