Hi,

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For the relay problem:

- I decided to try the disassembly again and it worked correctly this time.

- step#1: remove the cover, there are two screws, one of which is hidden under the label.

- step #2: you have to dismantle the relay coil to go further and it is difficult.

- step#3: I had no choice but to cut the screw head, drill and remove the debris from the screw. The replacement screw was a 2-56.

- step #4 and #5, shows the RF base including the mechanics of the relay without the activation coil.

- step #6: dismantling the external mechanics of the relay.

- step #7: separation of the RF and mechanical part of the relay. At this point the goal was to clean the gold-plated blades and contacts and reassemble that part. Reassembly was quite difficult because it requires precision. After this step was done, I tested with the VNA and when I manually pushed on the blade above the spring that we see in steps #8 and #9, everything was going well with the VNA.

- After step #7, I redid the assembly without the cover and tested everything to realize that it was not yet working correctly.

- I ended up understanding that the problem was the distance between the blade pushing on the spring base which didn't have enough pressure. So I did the disassembly in step #6, I adjusted the thin blade attached to a metal part, so that the blade barely touches the base of the spring as shown in step #9... and this solved the problem.

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So, here is my advice: do steps 1,2 and 3 and look at the blade shown in 8 and 9. If it does not touch the base of the spring, do step 6, adjust the blade to get a result like step 9 and reassemble everything without the cover and do a test on your workbench. The relay operates at +15V (97mA), pay attention to polarity. The test can be done with an oscilloscope, if you do not have a VNA or Spectrum. Choose a low frequency for the test first, for example 50 MHz, you will quickly see if the signal passes when the relay is activated. If unfortunately, the relay still has the same erratic behavior, then you will have to go further and do step 7...and that is not easy at all.

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I did the same test as you to compare, and it's difficult to explain this behavior.

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I also did this automated performance test, which is the error of the output frequency vs the programming of that frequency.

The acceptance limit is ±0.5%, but typically the error should be close to ±0.1%. This test checked all programmable frequencies from 31.3MHz to 3.5GHz in steps of 100kHz, therefore 34688 frequencies, so this test lasted several hours. The error result also includes that of thermal drift during the test.

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Tomorrow I'm going to go see a friend to do a comparative test regarding frequency stability on another 8133A.

I will probably have the opportunity to do a test on a Tektronix 11801B with SD-26 and I will check the trigger mode with a signal from the 8133A. I will give you my comments if this test can ever be done.

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Yeah,

I did ran the command and I get following, so It seems calibration is OK (it is linear)

:DIAG:CAL:YIG?
+2.02000E+09,+9.55000E+02,+2.56030E+09,+1.54500E+03,+3.02723E+09,+2.05600E+03,+3.49605E+09,+2.56700E+03,+3.95992E+09,+3.07200E+03

I re measured and plotted the set frequency and the output frequency on ch1 (using frequency counter). I see below plot. Yellow trace is the YIG frequency from 2 to 4Ghz (expected) and the blue trace is the actual frequency output, x axis is the set frequency. I measured manually from 33 Mhz to 500Mhz. Its clear that the output frequency has some issues and not linear with set frequency.


I still do not understand how 12 bit DAC translates to the YIG output, May be some bit of DAC is an issue?.

By the way, My timing board was coming from Israel, and due to what's going on over there, it is not certain if I will get it or not.?

If you end up fixing RF relay, then I will follow your pursuit and fix mine also. :)

Thanks alot.