Given that I apparently collect old measurement instruments, here follows some info that may not appear obvious:
HP 11729C Phase noise testset – Get option 130, avoid the rest as these remove functions. This box is more or less a collection of parts, not a complete instrument. Disconnecting the AGC IF amplifier, and moving this so that it is only used on the microwave bands gives better performance. If you want to measure oscillators below 50MHz, install a 2-3MHz LPF in front of the low noise amplifier or this will saturate because of the 2F product from the phase detector.
HP8970A Noise figure meter – E80 and E26 is the backup battery. This is a CR2025. (Old meters with an analog meter may have a 3V NiMh that leaks). Change battery, then connect a 15dB ENR noise source and key in SP 33.0 to have the meter generate its new cal constants. Simon suggests using a 2.6A primary lithium battery. if you can, avoid the A version, the B version has some features like plots via GPIB, and support for 8971A.
HP 8662A Signal Generator – If status is 99, and BLUE + status gives 04 or 05 it’s probably LF sum loops. These are notorious for drifting, and dead capacitance diodes. There is no reasonable replacement for the diodes to hold the specified phase noise, so time to get a parts unit. Unless you need it for the 11723 or similar phase noise measurements, it may be worth looking at other generators. Make sure to clean card connectors with isopropyl alcohol when servicing them.
HP8660A/B/C Signal Generator – Avoid A and B versions like the plague. Both soldering problems and logic that randomly dies due to lack of process control. Unless you have the 18GHz plugin, there are better generators around.
Tektronix 492A /B Spectrum Analysator – Try to get the B version or the 494A since this has better oscillator control, and allows use of a 10MHz reference. KE5FX has a good document describing the common problems.
HP141 Spectrum Analysator – worthwhile to have if you can spare the space, and accept that there is no readout, nor locking of the LO. Uses only chips that are common catalog parts, making repairs easy. Will require changing capacitors as they dry out. A method of transferring the screen to the computer can be done with a arduino or similar driving the analog sweep input and reading the Y out. Some analog parts are needed to convert the signals and interface with the microcontroller.
HP8566A/B and HP 8568A/B These uses the same IF/Display unit. To power Display without RF section, jumper A1A8TP1 to A1A8TP2. To generate the test pattern, jumper A3A6TP3 to A3A6TP6. Press the small white reset button on A3A7 and the picture should come to life.
For all of the instruments, when fault-finding, start by confirming the voltages from the power supplies. Confirming that the ripple is low, and that the electrolytic capacitors is ok with a scope should be the next step. Make sure that all card connectors are cleaned. I use isopropyl alcohol on a regular typing paper, and rub this over the contacts.
Extenders for HP card edge boards are found on eBay. both original and reproductions. Extenders for Tektronix 490 series may be available from Matt North at Norway labs in Portland, Oregon, USA.
RF and electronics blog LA3PNA 