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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But as I had never used an C before, I was not aware that the Hp8753d 1 should be yellow instead of orange But I could not find it for a while, until I got the info from another manyal of an C, where it was pictured. I could not believe my eyes.

Here you have the previous apparently good check of the YO coil drive, which showed some offset: As you can see, I was right about the offset being an anomaly.

8753C Network Analyzer, 30 kHz to 3 GHz

I hp88753c a scope with a DC input to the pin 2 and It was complete inside I had no way to know before getting the unit, so that was a very welcomed thing and some parts were obviously working, as power supply, fan, CPU, keyboard, display and so on.

Here you have a test pattern displayed on the Sony monitor subassembly yes, it is a Sony Trinitron tube!

The problem was with the device not powering on or restarting unexpectedly. The following part of the schematic shows the critical elements of the PWM controller. 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.

Unit as received I got the unit knowing it had several faults, so there was not surprise when I got the first display from it: The controller board before the fix. The Service Manual instructs to remove the boards nanual by one to identify which one may be causing the overload condition, which I did with no success.

EB5AGV’s Workbench: HP-8753C repair

You can see from page of the PDF what the different displays should be in a working janual. The bad C6 bypass capacitor was replaced with a new mica red one which can be seen in the center of the picture. The difference between the two was amplified and steered the PWM to regulate the output voltage of the pre-regulator. I hope you enjoy it!


If the overload condition was still present it caused the device to continuously cycle the power. Setting Observed frequency Error approx hp875c3 When the power switch was activated, the VNA appeared to be starting up but as soon as the CRT bp8753c was about to come up it produced a hissing sound and the device shut down and immediately restarted in a continuous loop.

Source adjustments As I said before, I was afraid of manul any test which would write on the configuration EEPROM, as I had no way to restore the previous configuration if things got worse But before doing them, I thought that a good way up8753c know if the rest of the system was OK, was to check the unit with an external reference.

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. Manula that the analyzer seemed to run fine with an external reference was a good thing, as it really pinpointed the A3 SOURCE as the real culprit.

Then all of a sudden the VNA began cycling the power again even with the display power disconnected. Here you have a sample display: The VNA class of instruments was not wide known to or used by the Ham Radio enthusiasts before recently because of very high cost of that h8p753c of equipment.

At least now the power supply was running and I was able to check the voltage and ripple levels on the pre- and post-regulators per the Service Manual and it all looked fine.

I soldered a new resistor in parallel to it but that did not help.

But as it runs on one side, internally to the frame, I needed to remove the display section to access it, so I left that for later work. During normal operations all the LEDs are on and start flashing when the shutdown circuitry detects a overcurrent, overvoltage or undervoltage condition.

Manuals – KO4BB

So that was a good starting point! Display color adjustment I had some info about the colors not being accurate on this unit. So I run all the tests which were related to it. Clicking sounds produced by the attenuator and switch relays could also be heard. I cut one of the legs off and connected the ohmmeter across the capacitor – it measured a resistance. Next step is to add an external storage unit to the VNA.


The board has LEDs along the jp8753c of the board that indicate power hp853c for each post-regulator channel. It was a small yellow axial 0. Also, it was unusual that this type of component, a small axial bypass capacitor, would develop resistance and caused that much of a problem, rendering the whole system unusable.

The Test Set basically has a frequency doubler to multiply the source signal frequency by 2, RF couplers on the two test ports and RF switches to swap the ports. So it appeared the problem was not in the display circuitry.

There was no a specific pattern that would allow to predict as to when this may happen next time. I got it out of the unit and, as expected, there were no external signs of problems. But I stopped early, as it suggested to do a recalibration and I was afraid that would only make things worse; I checked the RF OUT in CW mode with an spectrum analyzer and an oscilloscope, at different frequencies. It mnaual became apparent that the problem may be with the PWM controller which for some reason restarted intermittently.

Thanks to the used equipment market for producing such a nice opportunity to learn. So when one dies on you it is not a good feeling.

EB5AGV’s Workbench: HPC repair

Cleaning works I have done also some cosmetic work on the unit and have also fixed the gummy power button system. More to come soon Here you have what I got: But with some determination and efforts even a very complex equipment can be repaired.

So, yes, it seemed like the VNA was working fine!!!