Tue, 28 Aug 2018 15:12:24 +0200
[prologix] minor improvments
101
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
1 | =============================================== |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
2 | HP8662A Synthetized Signal Generator - Part 3 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
3 | =============================================== |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
4 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
5 | :Author: David Douard |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
6 | :Category: Electronics |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
7 | :Tags: HP8662A, repair, test equipment, HP, Generator, RF |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
8 | :series: HP 8662A |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
9 | :series_index: 3 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
10 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
11 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
12 | This is the part 3 on my series about my HP 8662A Signal Generator, and is |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
13 | about the third main problems I found with this unit, as evocated in `part |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
14 | 2 <{filename}hp8662a_2.rst>`_: Error 04 is lit and there are some very |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
15 | unpleasant spectrums at some frequencies. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
16 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
17 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
18 | Low Fequency Section |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
19 | ==================== |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
20 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
21 | If the generator is now able to produce a signal (the AM and FM modulations |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
22 | also work), it also gives an Error 04, which is described in the Service Manual |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
23 | as "Sum Loop Unlocked (Low Frequency Section)", and the troubleshooting |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
24 | procedure to follow in on the Service Sheet H. The general block diagram of |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
25 | this section is as follow: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
26 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
27 | .. image:: {filename}images/hp8662a/LF_block_diagram.png |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
28 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
29 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
30 | This Low Frequency Section consists in no less than 4 phase locked loops in |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
31 | order to achieve adjustable frequency synthesis with the expected stability and |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
32 | resolution. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
33 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
34 | In fact, when in the main band of the generator, ie. when neither the output |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
35 | frequency doubler nor the down converter are in the signal path (that is, when |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
36 | the frequency range is between 120MHz and 640MHz). The frequency display |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
37 | consists in 11 digits, named DF0 to DF10, which are segmented to control |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
38 | several sets of PLLs: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
39 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
40 | :DF0 - DF2: are the fractional part of the fractional N-Loop (.1Hz, 1Hz and |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
41 | 10Hz digits), |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
42 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
43 | :DF3 - DF5: are the integer part of the fractional N-loop (100Hz, 1kHz and |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
44 | 10kHz resolutions) |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
45 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
46 | :DF6 - DF7: are used to set the pretune VCO value for the sum loop VCO (A3A7), |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
47 | the FM sum loop VCO (A3A8) as well as the N-Loop VCO (A3A4). These |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
48 | are the 0.1MHz and 1MHz resolution digits. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
49 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
50 | :DF8 - DF9: these control the high frequency section (DF10 can only be 0 or 1, |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
51 | in which case the frequency doubler is used). |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
52 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
53 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
54 | Here is a more detailed vue of the block diagram of the low frequency section: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
55 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
56 | .. image:: {filename}images/hp8662a/sheet_H.png |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
57 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
58 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
59 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
60 | Fixing the Error 04 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
61 | =================== |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
62 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
63 | The service manual describes the Error 04 as related to the Sum Loop, and the |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
64 | first troubleshooting step is to adjust the LF Sum Loop VCO on A3A7. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
65 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
66 | To do this, one must open the loop of the PLL to be able to adjust the |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
67 | frequency-to-voltage curve of the VCO. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
68 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
69 | It took me a while to really understand the service manual on this point, as it explains: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
70 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
71 | Remove the two jumpers on the A3A7 VCO Assembly a n d plug the board back |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
72 | into its socket. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
73 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
74 | The problem is that there are no jumpers on that board... In fact, these |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
75 | jumpers exists, but are just soldered wires, and not, as one would expect, |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
76 | jumpers that can be easily unplugged. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
77 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
78 | Once I finally understood this, I've been able to perform this adjustment. This |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
79 | consists in tweaking two potentiometers to tune both ends of this |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
80 | frequency/voltage curve. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
81 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
82 | The ideal curve is (all frequencies are in MHz): |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
83 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
84 | ===== =========== ========= ========= |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
85 | Freq N-Loop VCO Sum L VCO FM SL VCO |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
86 | +/- 3MHz +/- 3MHz +/- .3MHz |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
87 | ===== =========== ========= ========= |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
88 | 320.0 122 120 10.0 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
89 | 320.1 123 121 10.1 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
90 | 320.2 124 122 10.2 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
91 | 320.4 126 124 10.4 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
92 | 320.8 130 128 10.8 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
93 | 321.0 132 130 11 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
94 | 322.0 142 140 12 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
95 | 324.0 162 160 14 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
96 | 328.0 202 200 18 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
97 | 329.9 221 219 19.9 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
98 | ===== =========== ========= ========= |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
99 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
100 | As you can see, ideal curves are pretty linear. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
101 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
102 | At first, I could not find a correct set of tunings: when I was setting the two |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
103 | ends of the curve to their ideal values (120MHz and 219MHz), the values for |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
104 | 324MHz and 328MHz did not match the +/- 3MHz criterion. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
105 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
106 | Here is the curve after I adjusted both ends to be as close as possible as |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
107 | their ideal values (the error is inversed to make the plot easier to read; most |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
108 | of the time, I am below the expected value): |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
109 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
110 | .. plotly:: {filename}/json/hp8662a_vco_sl.json |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
111 | :width: 800 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
112 | :height: 600 |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
113 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
114 | As you can see, the +/- 3MHz band is not achieved for most part of the curve. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
115 | And it looks pretty bad since the max error is above 6MHz. However, I |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
116 | compensated this by overshooting these two points as much as possible in order |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
117 | to try to keep the whole curve within this +/- 3MHz band. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
118 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
119 | Unfortunately I haven't taken numerical values after this tuning, since this |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
120 | was enough to clear the Error 04. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
121 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
122 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
123 | Other unstable PLLs |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
124 | =================== |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
125 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
126 | After this adjustement, the generator seems to works fine: it does produces a |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
127 | nice output signal (well, I though) and gives no more error. But eventually, |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
128 | playing with the sweep controls, I found some pretty nasty behaviors at some |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
129 | ferquencies. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
130 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
131 | For example, at 100.3MHz, we have a decent signal: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
132 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
133 | .. image:: {filename}/images/hp8662a/working_not_quite_3.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
134 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
135 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
136 | .. image:: {filename}/images/hp8662a/working_not_quite_3_sa.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
137 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
138 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
139 | but at 101.0Mhz, it begins to looks pretty messy: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
140 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
141 | .. image:: {filename}/images/hp8662a/working_not_quite_2.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
142 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
143 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
144 | .. image:: {filename}/images/hp8662a/working_not_quite_2_sa.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
145 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
146 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
147 | and 101.9Mhz shows "nice" side bands: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
148 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
149 | .. image:: {filename}/images/hp8662a/working_not_quite.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
150 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
151 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
152 | .. image:: {filename}/images/hp8662a/working_not_quite_sa.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
153 | :class: image-process-large-photo |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
154 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
155 | The problem seems quite clear: some PLL cannot lock at specific frequencies, |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
156 | but the strange thing is that this unlock PLL does not produces an error. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
157 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
158 | So I tried to figure out which boad assembly could be the culprit. With no |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
159 | error however, I had to troubleshoot without a procedure. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
160 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
161 | The funny thing was there was not clear 'pattern' of which frequencies produces |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
162 | the erratic behavior and which worked fine. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
163 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
164 | The problematic ranges were clearly cyclic upon the frequency range, but the |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
165 | limits were not very stable. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
166 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
167 | I spent a fait amount of time reading the service manual and reading the |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
168 | schematics to try to understand which board could be the culprit, and measuring |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
169 | value at any testpoint possible... |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
170 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
171 | At the end, as I did not make any progress, I decided to try to make all the |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
172 | "post-reapir" adjustments related to the Low Frequency section. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
173 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
174 | And when I finally tuned the FM Sum Loop VCO, for the procedure is very similar |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
175 | to the Sum Loop VCO one, the problem disappeared. |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
176 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
177 | For example, a 101MHz signal which was very unstable before now looks like: |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
178 | |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
179 | .. image:: {filename}/images/hp8662a/working_101.jpg |
4a94e81bff74
[hp8662a] part 3: fixing error 04 and unlocked loops
David Douard <david.douard@logilab.fr>
parents:
diff
changeset
|
180 | :class: image-process-large-photo |