Reapair & Calibration of HP8485A 26.5GHz power sensor & HP437B Meteter Microwave measurements.

We repair a defective HP8485A 26.5GHz RF Power Sensor that refuses to Zero & its meter HP437B & calibrate the N port cal signal against the Marconi 6204B Microwave Test Set, (Scalar Analyser) utilising a Marconi 6910 power sensor for reference since this Marconi kit is calibrated we use the Marconi test gear to calibrate the HP Meter & confirm its sensors are accurate.

[@digitalradiohacker]

I bought an Anritsu Sitemaster S331 on Ebay a few years ago.
It was "for parts not working" and wouldn't switch on, but it came with the padded case, software (floppy disc I think) serial lead, phase-stable patch lead, OSL standards all in the factory supplied peli case.
Turns out that the battery had leaked on the PCB in the meter, and had rotted a few traces. Those traces were non-critical logic circuits, so it was an easy fix with some bodge wires. While it was apart, I put a new battery pack together with something like 10x the capacity (runs the meter for weeks between charges).
The lovely Anritsu power sensor that came with it all lasted about a week before I connected a UHF handheld radio and chucked 4W up it with no attenuator. The INSTANT I pressed the PTT, I released it and sucked air in through my teeth. Yep - toast.
My tip for people working with the same radio gear day in and day out is to put a pair of attenuators on the sensor, and leave them there. The idea is, if you connect a 50w mobile / repeater, the attenuators will scale things to be safe and measurable. If you want to measure a 4w handset, you have to go to some extra effort to remove one of the attenuators every single time. Done this way, you have to go to extra effort to make the sensor vulnerable, rather than having to go to extra effort to make it safe.

[@talebbachir869]

Tnx good work

[@TheGmr140]

Nice power meter

[@willthecat3861]

The older "HP 8485A Power Sensor Operating and Service Manual" and the newer "Keysight 8480 Series Coaxial Power Sensors Operating and Service Manual" have exploded drawings, instructions on how to open the case, and circuit diagrams. And yes, many a 8485 HP power sensor has been destroyed through severing the gold wire(s) connecting the thermocouple ... usually by people who can't be bothered to read the excellent free docs.

[@willthecat3861]

Those are APC-3.5 mm connectors, I believe.

[@willthecat3861]

I don't see how the gold can "melt" because of soldering. Gold melts at around 2000 F and tin lead solder at about 500 F. Do you mean that the gold dissolves into the solder? HP used to... long ago, gold plate the tracks of PCB. Solder worked fine there.

[@zdzisiek1979]

Czy miernik HP437B posiada baterię litową 3V ? Pozdrawiam

[@willthecat3861]

I agree...many a HP power sensor has had the thermocouple, or the diodes, blown into low earth orbit, by connecting them to too much power. It only takes a second, and that's the end of the thermocouple. That includes connecting them to the cal output on the power meters, without the 'reference' attenuator that is supposed to be used with some of them. Long ago, HP used to sell kits, so users could replace them...but that's long ago. If you pop it... it's done. You can't fix it. Many for sale, as for 'parts or repair' The part you most often need for the repair is the thermocouple (or diodes), and that's usually blown in these. Don't buy them.