comparison: content/hp8662a_3.rst
content/hp8662a_3.rst
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| 9 :series_index: 3 | 9 :series_index: 3 |
| 10 | 10 |
| 11 | 11 |
| 12 This is the part 3 on my series about my HP 8662A Signal Generator, and is | 12 This is the part 3 on my series about my HP 8662A Signal Generator, and is |
| 13 about the third main problems I found with this unit, as evocated in `part | 13 about the third main problems I found with this unit, as evocated in `part |
| 14 2 <{filename}hp8662a_2.rst>`_: Error 04 is lit and there are some very | 14 2 <{static}hp8662a_2.rst>`_: Error 04 is lit and there are some very |
| 15 unpleasant spectrums at some frequencies. | 15 unpleasant spectrums at some frequencies. |
| 16 | 16 |
| 17 | 17 |
| 18 Low Fequency Section | 18 Low Fequency Section |
| 19 ==================== | 19 ==================== |
| 22 also work), it also gives an Error 04, which is described in the Service Manual | 22 also work), it also gives an Error 04, which is described in the Service Manual |
| 23 as "Sum Loop Unlocked (Low Frequency Section)", and the troubleshooting | 23 as "Sum Loop Unlocked (Low Frequency Section)", and the troubleshooting |
| 24 procedure to follow in on the Service Sheet H. The general block diagram of | 24 procedure to follow in on the Service Sheet H. The general block diagram of |
| 25 this section is as follow: | 25 this section is as follow: |
| 26 | 26 |
| 27 .. image:: {filename}images/hp8662a/LF_block_diagram.png | 27 .. image:: {static}images/hp8662a/LF_block_diagram.png |
| 28 :class: image-process-large-photo | 28 :class: image-process-large-photo |
| 29 | 29 |
| 30 This Low Frequency Section consists in no less than 4 phase locked loops in | 30 This Low Frequency Section consists in no less than 4 phase locked loops in |
| 31 order to achieve adjustable frequency synthesis with the expected stability and | 31 order to achieve adjustable frequency synthesis with the expected stability and |
| 32 resolution. | 32 resolution. |
| 51 in which case the frequency doubler is used). | 51 in which case the frequency doubler is used). |
| 52 | 52 |
| 53 | 53 |
| 54 Here is a more detailed vue of the block diagram of the low frequency section: | 54 Here is a more detailed vue of the block diagram of the low frequency section: |
| 55 | 55 |
| 56 .. image:: {filename}images/hp8662a/sheet_H.png | 56 .. image:: {static}images/hp8662a/sheet_H.png |
| 57 :class: image-process-large-photo | 57 :class: image-process-large-photo |
| 58 | 58 |
| 59 | 59 |
| 60 Fixing the Error 04 | 60 Fixing the Error 04 |
| 61 =================== | 61 =================== |
| 105 | 105 |
| 106 Here is the curve after I adjusted both ends to be as close as possible as | 106 Here is the curve after I adjusted both ends to be as close as possible as |
| 107 their ideal values (the error is inversed to make the plot easier to read; most | 107 their ideal values (the error is inversed to make the plot easier to read; most |
| 108 of the time, I am below the expected value): | 108 of the time, I am below the expected value): |
| 109 | 109 |
| 110 .. plotly:: {filename}/json/hp8662a_vco_sl.json | 110 .. plotly:: {static}/json/hp8662a_vco_sl.json |
| 111 :width: 800 | 111 :width: 800 |
| 112 :height: 600 | 112 :height: 600 |
| 113 | 113 |
| 114 As you can see, the +/- 3MHz band is not achieved for most part of the curve. | 114 As you can see, the +/- 3MHz band is not achieved for most part of the curve. |
| 115 And it looks pretty bad since the max error is above 6MHz. However, I | 115 And it looks pretty bad since the max error is above 6MHz. However, I |
| 128 playing with the sweep controls, I found some pretty nasty behaviors at some | 128 playing with the sweep controls, I found some pretty nasty behaviors at some |
| 129 ferquencies. | 129 ferquencies. |
| 130 | 130 |
| 131 For example, at 100.3MHz, we have a decent signal: | 131 For example, at 100.3MHz, we have a decent signal: |
| 132 | 132 |
| 133 .. image:: {filename}/images/hp8662a/working_not_quite_3.jpg | 133 .. image:: {static}/images/hp8662a/working_not_quite_3.jpg |
| 134 :class: image-process-large-photo | 134 :class: image-process-large-photo |
| 135 | 135 |
| 136 .. image:: {filename}/images/hp8662a/working_not_quite_3_sa.jpg | 136 .. image:: {static}/images/hp8662a/working_not_quite_3_sa.jpg |
| 137 :class: image-process-large-photo | 137 :class: image-process-large-photo |
| 138 | 138 |
| 139 but at 101.0Mhz, it begins to looks pretty messy: | 139 but at 101.0Mhz, it begins to looks pretty messy: |
| 140 | 140 |
| 141 .. image:: {filename}/images/hp8662a/working_not_quite_2.jpg | 141 .. image:: {static}/images/hp8662a/working_not_quite_2.jpg |
| 142 :class: image-process-large-photo | 142 :class: image-process-large-photo |
| 143 | 143 |
| 144 .. image:: {filename}/images/hp8662a/working_not_quite_2_sa.jpg | 144 .. image:: {static}/images/hp8662a/working_not_quite_2_sa.jpg |
| 145 :class: image-process-large-photo | 145 :class: image-process-large-photo |
| 146 | 146 |
| 147 and 101.9Mhz shows "nice" side bands: | 147 and 101.9Mhz shows "nice" side bands: |
| 148 | 148 |
| 149 .. image:: {filename}/images/hp8662a/working_not_quite.jpg | 149 .. image:: {static}/images/hp8662a/working_not_quite.jpg |
| 150 :class: image-process-large-photo | 150 :class: image-process-large-photo |
| 151 | 151 |
| 152 .. image:: {filename}/images/hp8662a/working_not_quite_sa.jpg | 152 .. image:: {static}/images/hp8662a/working_not_quite_sa.jpg |
| 153 :class: image-process-large-photo | 153 :class: image-process-large-photo |
| 154 | 154 |
| 155 The problem seems quite clear: some PLL cannot lock at specific frequencies, | 155 The problem seems quite clear: some PLL cannot lock at specific frequencies, |
| 156 but the strange thing is that this unlock PLL does not produces an error. | 156 but the strange thing is that this unlock PLL does not produces an error. |
| 157 | 157 |
| 174 And when I finally tuned the FM Sum Loop VCO, for the procedure is very similar | 174 And when I finally tuned the FM Sum Loop VCO, for the procedure is very similar |
| 175 to the Sum Loop VCO one, the problem disappeared. | 175 to the Sum Loop VCO one, the problem disappeared. |
| 176 | 176 |
| 177 For example, a 101MHz signal which was very unstable before now looks like: | 177 For example, a 101MHz signal which was very unstable before now looks like: |
| 178 | 178 |
| 179 .. image:: {filename}/images/hp8662a/working_101.jpg | 179 .. image:: {static}/images/hp8662a/working_101.jpg |
| 180 :class: image-process-large-photo | 180 :class: image-process-large-photo |
