This manual may contain references to HP or Hewlett-Packard. Please note that Hewlett-. Packard’s former test and measurement, semiconductor products and. Chapter 2 Getting Acquainted with the HP C How to Get the Most Out of the HP C “General Information” section of the Operating Manual has. This page is devoted to the repair of my HPC Network Analyzer. section or page of the HPC Service Manual PDF file) and got these results.
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It was not hard, using the extensive display charts tests, to get the colors more natural, as chart 13 shows: It seemed to have a good level and it was variable as it shouldbut frequency was way out and only changed in large steps this could be a hint on the problem, I guessed.
The construction of the switching power supply is interesting and deserves a larger photo. More to come soon Doing some extra checkings This kind of microprocessor controlled systems, even manhal 20 years old inhave usually a large quantity of self checks which save a lot of time measuring here and there.
To check my theory, Manuual soldered a new 0. To do that, I have got out the display assembly, have carefully cleaned it, and then have cleaned and greased the power button mechanism: It can be seen in the above picture along the edge of the right half of the box. That puzzled me off completely. Every once in a while the C was able to start and work for a period of time and then all of a sudden restarted as was described above. Here you have the apparently good check of the YO coil drive: The device has a switching pre-regulator encased in a separate box and the post-regulator removable board with all the secondary linear regulators.
You can see from page of the Maunal what the different displays should be in mankal working unit. Basically, the unit was mechanically sound, except for the missing display buttons cover an spare is already on its way: Other smaller problem was that the power switch was semi-stuck, mqnual a gummy touch, making it very hard to power up and down the unit.
EB5AGV’s Workbench: HPC repair
It can be seen from the schematic that this voltage is supposed to be stable and present on the pin 2 all of the time as long as the VNA power switch is turned on. And manula results were, as you can imagine, bad at least for the first one; the other ones seem to be similar to what the manual says, but with some offsets. During normal operations all the LEDs are on and mqnual flashing when the shutdown circuitry detects a overcurrent, overvoltage or undervoltage condition.
That oscillator is a 3. When the power switch was activated, mxnual VNA appeared to be starting up but as soon as the CRT display was about to come up it produced a hissing sound and the device shut down and immediately restarted in a continuous loop.
So I run all the tests which were related to it. So I proceeded with some hesitation and hoping for the best But as I had never used an C before, I was not aware that the Channel 1 should be yellow instead of orange So I removed the switching pre-regulator box and opened it in a hope to find the answer there.
I cut one of the legs off and connected the ohmmeter across the capacitor – it measured a resistance. I marked with a permanent pen the actual position, so I had a reference to come back if I goofed the adjustment too much.
It then became apparent that the problem may be with the PWM controller which for some reason restarted intermittently. Hoping that the other few hundred bypass capacitors of this type in the VNA will have been doing fine for the next 10 years or so.
Good example of something being at the wrong place at the wrong time! In the picture on the right the post-regulator board can be seen in the middle of the frame by the back panel. The bad C6 bypass capacitor was replaced with a new mica red one which can be seen in the center of the picture.
I got a gut feeling that the problem may be with the power supply itself.
Here you have the pots: The two halves of the box have connections with each other via disconnectable wire cables. Next step is to add an external storage unit to the VNA. The left half of the box had the power stage and rectifiers. I looked at the mechanism and there was lot of old grease on it.
The display looks really nice, which is a plus for a 20 year old instrument Locating the faulty assembly I got the CPU board out of the unit, trying to locate a jumper which is named in the Service Manualbut no joy. The difference between the two was amplified and steered the PWM to regulate the output voltage of the pre-regulator.
8753C Network Analyzer, 30 kHz to 3 GHz
The bad C6 capacitor is the yellow one in the middle of the picture to the left of the controller IC pin 2. The easy-to-use softkey selection of measurement functions allows you to measure the magnitude, phase, or group delay characteristics of your device under test.
I was stunned – a one penny capacitor took down the multi-K dollar device. Here you have a sample display: That was the breakthrough and I realized that the shutdown condition was caused not by a overcurrent but by a undervoltage.