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| 1 ========================================== | |
| 2 HP3562A Dynamic Signal Analyzer - Part 4 | |
| 3 ========================================== | |
| 4 | |
| 5 :Author: David Douard | |
| 6 :Category: Electronics | |
| 7 :Tags: HP3562A, HP1345A, repair, test equipment, DSA | |
| 8 :series: HP 3562A | |
| 9 :series_index: 4 | |
| 10 | |
| 11 This is the part 4 of the series about my | |
| 12 `HP 3562A Digital Signal Analyzer <{filename}hp3562a.rst>`_, | |
| 13 quickly describing the HP 1345A Digital Display unit as well as | |
| 14 the repair I had to do on it. | |
| 15 | |
| 16 | |
| 17 Display | |
| 18 ======= | |
| 19 | |
| 20 The display unit is a HP1345A Digital Display without the option 714 | |
| 21 (wich adds a 4K x 16 bits Vector Memory), so it must driven by a | |
| 22 dedicated display controller (which is on the A38 memory board): | |
| 23 | |
| 24 .. image:: {filename}images/hp3562a/a8_a17_display.png | |
| 25 | |
| 26 The unit is a 6 inch monochrome display producing true vector graphics | |
| 27 with a resolution of 2048x2018 points. It can display up to 3226 | |
| 28 inches of vectors at 60Hz. It also embeds a character generator. | |
| 29 | |
| 30 It's a true vector display; vectors are drawn by moving the CRT beam | |
| 31 on the screen (it's not a pixel based display). | |
| 32 | |
| 33 .. image:: {filename}images/hp3562a/hp1345a_raster_vector.png | |
| 34 | |
| 35 It can diplay: | |
| 36 | |
| 37 - solid lines | |
| 38 - solid lines with intensified end points | |
| 39 - short dashed lines | |
| 40 - long dashed lines | |
| 41 - dots at end points | |
| 42 | |
| 43 with 3 differents visible brightness levels. It also allows to specify | |
| 44 4 beam velocities: | |
| 45 | |
| 46 - 0.13cm/µs | |
| 47 - 0.25cm/µs | |
| 48 - 0.38cm/µs | |
| 49 - 0.51cm/µs | |
| 50 | |
| 51 Allowing more brightness control of the vectors. | |
| 52 | |
| 53 .. image:: {filename}images/hp3562a/hp1345a.jpg | |
| 54 | |
| 55 | |
| 56 If not connected with a controller, it shows a test pattern for | |
| 57 adjustments. | |
| 58 | |
| 59 .. image:: {filename}images/hp3562a/hp1345a_test_pattern.png | |
| 60 | |
| 61 The unit looks like: | |
| 62 | |
| 63 .. image:: {filename}images/hp3562a/hp1345a_side.jpg | |
| 64 | |
| 65 .. image:: {filename}images/hp3562a/hp1345a_side2.jpg | |
| 66 | |
| 67 .. image:: {filename}images/hp3562a/hp1345a_top.jpg | |
| 68 | |
| 69 | |
| 70 Adjustment and repair | |
| 71 --------------------- | |
| 72 | |
| 73 While the instrument was apart, I wanted to see if I can recalibrate | |
| 74 the display, especially try to adjust the overall brightness of the | |
| 75 CRT since mine is a bit dimm (I have to set the intensity knob FCW to | |
| 76 see the whole picture). I also wanted to improve a bit the focus and | |
| 77 precision of the lines. | |
| 78 | |
| 79 So I took the display unit off the instrument, which is | |
| 80 straighforward, powered it using my benchpower supplies, and began to | |
| 81 read the adjustment procedure and turn the pots, when suddenly the | |
| 82 display shut off. | |
| 83 | |
| 84 Using an ohmmeter, the diagnostic was easy: the +15v and -15v rails on | |
| 85 the A1 board were short. Fortunately, the schematic is available, so I | |
| 86 started to look for all decoupling capacitors (directly connected | |
| 87 between a power rail and the ground). It took me a little while before | |
| 88 identifing the real culprits, since the only solution to check them is | |
| 89 to desolder (at least one end): A1C45 and A1C48. | |
| 90 | |
| 91 .. image:: {filename}images/hp3562a/hp1345a_dead_caps.jpg | |
| 92 | |
| 93 | |
| 94 These 2 small (tantalum) caps near U3 were short. Not sure why they | |
| 95 died when I powered the display unit with my power supplies, maybe I | |
| 96 set them to a bit higher voltage then what the HP3562A generates. | |
| 97 | |
| 98 I replaced them with the closer spare I found (4.7µF tantalum caps), | |
| 99 and the Display Unit was up and running again. | |
| 100 | |
| 101 I knows these old tantalum caps are prone to fail, and I should | |
| 102 probably change them all, but I don't have enough spare for now. | |
| 103 | |
| 104 After that, I could resume my adjustement procedure. And indeed there | |
| 105 is an adjustment that allowed me to improve noticebly the brightness | |
| 106 of the screen (the Intensity Cut-Off Level). Now I can run my HP3562A | |
| 107 without the intensity knob FCW. | |
| 108 | |
| 109 | |
| 110 Brief description | |
| 111 ----------------- | |
| 112 | |
| 113 .. image:: {filename}images/hp3562a/hp1345a_block_diagram.png | |
| 114 | |
| 115 .. image:: {filename}images/hp3562a/hp1345a_stroke_generator.png | |
| 116 | |
| 117 | |
| 118 .. image:: {filename}images/hp3562a/hp1345a_ramp_generator.png | |
| 119 | |
| 120 | |
| 121 .. image:: {filename}images/hp3562a/hp1345a_vector_processor.png | |
| 122 | |
| 123 .. image:: {filename}images/hp3562a/hp1345a_vpc_architecture.png | |
| 124 | |
| 125 | |
| 126 |
