comparison: content/hp8662a.rst
content/hp8662a.rst
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| 40 So I gave a more detailed look inside the unit, not only the PSU. I found the | 40 So I gave a more detailed look inside the unit, not only the PSU. I found the |
| 41 unit so dirty inside I decided to take it apart as far as I can to clean it | 41 unit so dirty inside I decided to take it apart as far as I can to clean it |
| 42 before even attempting to fix the PSU. | 42 before even attempting to fix the PSU. |
| 43 | 43 |
| 44 .. image:: {filename}images/hp8662a/dirty_hp.jpg | 44 .. image:: {filename}images/hp8662a/dirty_hp.jpg |
| 45 :class: image-process-large-photo | |
| 45 | 46 |
| 46 | 47 |
| 47 And I must say that if most of the unit is very easy to service due to the | 48 And I must say that if most of the unit is very easy to service due to the |
| 48 modular design of all RF modules, making is very easy to remove all the boards | 49 modular design of all RF modules, making is very easy to remove all the boards |
| 49 and modules, there are also many parts that are connected together with wires | 50 and modules, there are also many parts that are connected together with wires |
| 50 soldered point to point, which makes disassembling the case, motherboards and | 51 soldered point to point, which makes disassembling the case, motherboards and |
| 51 so very tedious. | 52 so very tedious. |
| 52 | 53 |
| 53 .. image:: {filename}images/hp8662a/top_before_2.jpg | 54 .. image:: {filename}images/hp8662a/top_before_2.jpg |
| 55 :class: image-process-large-photo | |
| 54 | 56 |
| 55 .. image:: {filename}images/hp8662a/bottom_before.jpg | 57 .. image:: {filename}images/hp8662a/bottom_before.jpg |
| 58 :class: image-process-large-photo | |
| 56 | 59 |
| 57 .. image:: {filename}images/hp8662a/front_after.jpg | 60 .. image:: {filename}images/hp8662a/front_after.jpg |
| 61 :class: image-process-large-photo | |
| 58 | 62 |
| 59 Also, there are hundreds of screws in this unit! it's insane. | 63 Also, there are hundreds of screws in this unit! it's insane. |
| 60 | 64 |
| 61 .. image:: {filename}images/hp8662a/top_after.jpg | 65 .. image:: {filename}images/hp8662a/top_after.jpg |
| 66 :class: image-process-large-photo | |
| 62 | 67 |
| 63 Whatever, I finally got to a point I could clean most of the parts of the unit, | 68 Whatever, I finally got to a point I could clean most of the parts of the unit, |
| 64 so I started to reassemble it. Unfortunately, I did not took enough pictures | 69 so I started to reassemble it. Unfortunately, I did not took enough pictures |
| 65 while the disassembling, so it took me some effort to have something that looks | 70 while the disassembling, so it took me some effort to have something that looks |
| 66 like an HP 8662A... | 71 like an HP 8662A... |
| 67 | 72 |
| 68 .. image:: {filename}images/hp8662a/reassembling_2.jpg | 73 .. image:: {filename}images/hp8662a/reassembling_2.jpg |
| 74 :class: image-process-large-photo | |
| 69 | 75 |
| 70 Once I had the structure of the generator back togother, with the back plane in | 76 Once I had the structure of the generator back togother, with the back plane in |
| 71 place but no other board nor module plugged in, I started to take care of the | 77 place but no other board nor module plugged in, I started to take care of the |
| 72 PSU. | 78 PSU. |
| 73 | 79 |
| 74 .. image:: {filename}images/hp8662a/reassembling_1.jpg | 80 .. image:: {filename}images/hp8662a/reassembling_1.jpg |
| 81 :class: image-process-large-photo | |
| 75 | 82 |
| 76 The PSU | 83 The PSU |
| 77 ======= | 84 ======= |
| 78 | 85 |
| 79 As I said, the first attempt to plug (and not even power on) the unit ended | 86 As I said, the first attempt to plug (and not even power on) the unit ended |
| 85 a small part of the control circuit of the main PSU. | 92 a small part of the control circuit of the main PSU. |
| 86 - The main switching power supply. The high voltage section is allways on, and | 93 - The main switching power supply. The high voltage section is allways on, and |
| 87 the mani switch on the front panel only activate the switching. | 94 the mani switch on the front panel only activate the switching. |
| 88 | 95 |
| 89 .. image:: {filename}images/hp8662a/PSU_simplified_schematic.jpeg | 96 .. image:: {filename}images/hp8662a/PSU_simplified_schematic.jpeg |
| 97 :class: image-process-large-photo | |
| 90 | 98 |
| 91 The 4 boards the PSU is made of are: | 99 The 4 boards the PSU is made of are: |
| 92 | 100 |
| 93 - a main board (A7A4) on which are the first stages of the AC rectification and | 101 - a main board (A7A4) on which are the first stages of the AC rectification and |
| 94 filtering, | 102 filtering, |
| 104 | 112 |
| 105 - a daughter board (A7A2) with the switching control circuit. The switching | 113 - a daughter board (A7A2) with the switching control circuit. The switching |
| 106 regulation being made on the 5.2V rail, which is not regulated by A7A1. | 114 regulation being made on the 5.2V rail, which is not regulated by A7A1. |
| 107 | 115 |
| 108 .. image:: {filename}images/hp8662a/PSU_block_diagram.jpeg | 116 .. image:: {filename}images/hp8662a/PSU_block_diagram.jpeg |
| 117 :class: image-process-large-photo | |
| 109 | 118 |
| 110 So I gave a close look at thes boards, beginning by the main board, the I found | 119 So I gave a close look at thes boards, beginning by the main board, the I found |
| 111 the culprit for the smoke: the input protection thermistor. Strangely, it still | 120 the culprit for the smoke: the input protection thermistor. Strangely, it still |
| 112 measures a decent resistance value, but hey. | 121 measures a decent resistance value, but hey. |
| 113 | 122 |
| 136 But when I tried to turn power on, the voltege OK green LEDs flickered once but | 145 But when I tried to turn power on, the voltege OK green LEDs flickered once but |
| 137 did not stay on, and the error LED did turn on. All the voltages produced by | 146 did not stay on, and the error LED did turn on. All the voltages produced by |
| 138 the inverter board were very low. Somethin was wrong. | 147 the inverter board were very low. Somethin was wrong. |
| 139 | 148 |
| 140 .. image:: {filename}images/hp8662a/PSU_inverter_schematic.jpeg | 149 .. image:: {filename}images/hp8662a/PSU_inverter_schematic.jpeg |
| 150 :class: image-process-large-photo | |
| 141 | 151 |
| 142 Looking at the schematics and the boards, I did find several failure points: | 152 Looking at the schematics and the boards, I did find several failure points: |
| 143 | 153 |
| 144 - one of the 2 150µH inductors on the 160VDC rails (L6 anf L7 on A7A3) ) looked | 154 - one of the 2 150µH inductors on the 160VDC rails (L6 anf L7 on A7A3) ) looked |
| 145 a bit odd to me: it was not sitting flat on the PCB, which it should for this | 155 a bit odd to me: it was not sitting flat on the PCB, which it should for this |
| 158 and so but are very expensive (and a bit hard to find): something like 15€ | 168 and so but are very expensive (and a bit hard to find): something like 15€ |
| 159 each. So for now, I've replaced it with a simple 5x20 glass fuse: not as | 169 each. So for now, I've replaced it with a simple 5x20 glass fuse: not as |
| 160 skookum but does the job for a few cents. | 170 skookum but does the job for a few cents. |
| 161 | 171 |
| 162 .. image:: {filename}images/hp8662a/broken_choke.jpg | 172 .. image:: {filename}images/hp8662a/broken_choke.jpg |
| 173 :class: image-process-large-photo | |
| 163 | 174 |
| 164 After these fixes, I reassembled the PSU and tried again: the result was quite | 175 After these fixes, I reassembled the PSU and tried again: the result was quite |
| 165 promising, but not a complete success: the PSU seemed to start, but very | 176 promising, but not a complete success: the PSU seemed to start, but very |
| 166 quickly stops itself with an error LED on: the overvoltage protection was | 177 quickly stops itself with an error LED on: the overvoltage protection was |
| 167 shuting down the power. | 178 shuting down the power. |
