comparison: content/hp8662a.rst
content/hp8662a.rst
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| 12 remember exactly in what condition it was advertized when I purchased it, but | 12 remember exactly in what condition it was advertized when I purchased it, but |
| 13 it was most probably advertized as non working (otherwise it would have been | 13 it was most probably advertized as non working (otherwise it would have been |
| 14 cheap enough, more, what the fun in buying properly working test equipment?) | 14 cheap enough, more, what the fun in buying properly working test equipment?) |
| 15 | 15 |
| 16 I wanted to make a break in my current other repair project, the `EIP 545B | 16 I wanted to make a break in my current other repair project, the `EIP 545B |
| 17 Microwave Fequency Meter <{filename}eip545b.rst>`_, also having a properly | 17 Microwave Fequency Meter <{static}eip545b.rst>`_, also having a properly |
| 18 working unit such as this incredible signal synthetizer would be quite useful | 18 working unit such as this incredible signal synthetizer would be quite useful |
| 19 to perform several adjustement tasks on the EIP 545B. | 19 to perform several adjustement tasks on the EIP 545B. |
| 20 | 20 |
| 21 Carrying the unit from my cellar to my appartement was some kind of a job: it's | 21 Carrying the unit from my cellar to my appartement was some kind of a job: it's |
| 22 a robust 30kg device I had to climb the 7 levels: no lift in the old | 22 a robust 30kg device I had to climb the 7 levels: no lift in the old |
| 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 | 44 |
| 45 .. image:: {filename}images/hp8662a/dirty_hp.jpg | 45 .. image:: {static}/images/hp8662a/dirty_hp.jpg |
| 46 :class: image-process-large-photo | 46 :class: image-process-large-photo |
| 47 | 47 |
| 48 | 48 |
| 49 And I must say that if most of the unit is very easy to service due to the | 49 And I must say that if most of the unit is very easy to service due to the |
| 50 modular design of all RF modules, making is very easy to remove all the boards | 50 modular design of all RF modules, making is very easy to remove all the boards |
| 51 and modules, there are also many parts that are connected together with wires | 51 and modules, there are also many parts that are connected together with wires |
| 52 soldered point to point, which makes disassembling the case, motherboards and | 52 soldered point to point, which makes disassembling the case, motherboards and |
| 53 so very tedious. | 53 so very tedious. |
| 54 | 54 |
| 55 .. image:: {filename}images/hp8662a/top_before_2.jpg | 55 .. image:: {static}/images/hp8662a/top_before_2.jpg |
| 56 :class: image-process-large-photo | 56 :class: image-process-large-photo |
| 57 | 57 |
| 58 .. image:: {filename}images/hp8662a/bottom_before.jpg | 58 .. image:: {static}/images/hp8662a/bottom_before.jpg |
| 59 :class: image-process-large-photo | 59 :class: image-process-large-photo |
| 60 | 60 |
| 61 .. image:: {filename}images/hp8662a/front_after.jpg | 61 .. image:: {static}/images/hp8662a/front_after.jpg |
| 62 :class: image-process-large-photo | 62 :class: image-process-large-photo |
| 63 | 63 |
| 64 Also, there are hundreds of screws in this unit! it's insane. | 64 Also, there are hundreds of screws in this unit! it's insane. |
| 65 | 65 |
| 66 .. image:: {filename}images/hp8662a/top_after.jpg | 66 .. image:: {static}/images/hp8662a/top_after.jpg |
| 67 :class: image-process-large-photo | 67 :class: image-process-large-photo |
| 68 | 68 |
| 69 Whatever, I finally got to a point I could clean most of the parts of the unit, | 69 Whatever, I finally got to a point I could clean most of the parts of the unit, |
| 70 so I started to reassemble it. Unfortunately, I did not took enough pictures | 70 so I started to reassemble it. Unfortunately, I did not took enough pictures |
| 71 while the disassembling, so it took me some effort to have something that looks | 71 while the disassembling, so it took me some effort to have something that looks |
| 72 like an HP 8662A... | 72 like an HP 8662A... |
| 73 | 73 |
| 74 .. image:: {filename}images/hp8662a/reassembling_2.jpg | 74 .. image:: {static}/images/hp8662a/reassembling_2.jpg |
| 75 :class: image-process-large-photo | 75 :class: image-process-large-photo |
| 76 | 76 |
| 77 Once I had the structure of the generator back togother, with the back plane in | 77 Once I had the structure of the generator back togother, with the back plane in |
| 78 place but no other board nor module plugged in, I started to take care of the | 78 place but no other board nor module plugged in, I started to take care of the |
| 79 PSU. | 79 PSU. |
| 80 | 80 |
| 81 .. image:: {filename}images/hp8662a/reassembling_1.jpg | 81 .. image:: {static}/images/hp8662a/reassembling_1.jpg |
| 82 :class: image-process-large-photo | 82 :class: image-process-large-photo |
| 83 | 83 |
| 84 The PSU | 84 The PSU |
| 85 ======= | 85 ======= |
| 86 | 86 |
| 92 before being able to actually use the device when turned on), This also power | 92 before being able to actually use the device when turned on), This also power |
| 93 a small part of the control circuit of the main PSU. | 93 a small part of the control circuit of the main PSU. |
| 94 - The main switching power supply. The high voltage section is allways on, and | 94 - The main switching power supply. The high voltage section is allways on, and |
| 95 the mani switch on the front panel only activate the switching. | 95 the mani switch on the front panel only activate the switching. |
| 96 | 96 |
| 97 .. image:: {filename}images/hp8662a/PSU_simplified_schematic.jpeg | 97 .. image:: {static}/images/hp8662a/PSU_simplified_schematic.jpeg |
| 98 :class: image-process-large-photo | 98 :class: image-process-large-photo |
| 99 | 99 |
| 100 The 4 boards the PSU is made of are: | 100 The 4 boards the PSU is made of are: |
| 101 | 101 |
| 102 - a main board (A7A4) on which are the first stages of the AC rectification and | 102 - a main board (A7A4) on which are the first stages of the AC rectification and |
| 112 (+/-100mV), -10V (/- 40mV) and -40V (+/-200mV), | 112 (+/-100mV), -10V (/- 40mV) and -40V (+/-200mV), |
| 113 | 113 |
| 114 - a daughter board (A7A2) with the switching control circuit. The switching | 114 - a daughter board (A7A2) with the switching control circuit. The switching |
| 115 regulation being made on the 5.2V rail, which is not regulated by A7A1. | 115 regulation being made on the 5.2V rail, which is not regulated by A7A1. |
| 116 | 116 |
| 117 .. image:: {filename}images/hp8662a/PSU_block_diagram.jpeg | 117 .. image:: {static}/images/hp8662a/PSU_block_diagram.jpeg |
| 118 :class: image-process-large-photo | 118 :class: image-process-large-photo |
| 119 | 119 |
| 120 So I gave a close look at thes boards, beginning by the main board, the I found | 120 So I gave a close look at thes boards, beginning by the main board, the I found |
| 121 the culprit for the smoke: the input protection thermistor. Strangely, it still | 121 the culprit for the smoke: the input protection thermistor. Strangely, it still |
| 122 measures a decent resistance value, but hey. | 122 measures a decent resistance value, but hey. |
| 124 The thermistor is described the old fashion way: it's a 5Ω @25°C with a | 124 The thermistor is described the old fashion way: it's a 5Ω @25°C with a |
| 125 temperature coefficient of -3.8%/°C. I did not find an exact replacement in my | 125 temperature coefficient of -3.8%/°C. I did not find an exact replacement in my |
| 126 junk parts; only a slighty highter value one (a XXX, which is more like | 126 junk parts; only a slighty highter value one (a XXX, which is more like |
| 127 20Ω @25°C). Not ideal, but for now, it seems to work fine. | 127 20Ω @25°C). Not ideal, but for now, it seems to work fine. |
| 128 | 128 |
| 129 .. image:: {filename}images/hp8662a/smoking_thermistor.jpg | 129 .. image:: {static}/images/hp8662a/smoking_thermistor.jpg |
| 130 :class: image-process-large-photo | 130 :class: image-process-large-photo |
| 131 | 131 |
| 132 After this first step forward, I was not confident enought to plug the boards | 132 After this first step forward, I was not confident enought to plug the boards |
| 133 back in place and try again (I am always worried when I repair switching | 133 back in place and try again (I am always worried when I repair switching |
| 134 PSUs... they can fail in flame and glory sometimes). So I checked all the | 134 PSUs... they can fail in flame and glory sometimes). So I checked all the |
| 145 | 145 |
| 146 But when I tried to turn power on, the voltege OK green LEDs flickered once but | 146 But when I tried to turn power on, the voltege OK green LEDs flickered once but |
| 147 did not stay on, and the error LED did turn on. All the voltages produced by | 147 did not stay on, and the error LED did turn on. All the voltages produced by |
| 148 the inverter board were very low. Somethin was wrong. | 148 the inverter board were very low. Somethin was wrong. |
| 149 | 149 |
| 150 .. image:: {filename}images/hp8662a/PSU_inverter_schematic.jpeg | 150 .. image:: {static}/images/hp8662a/PSU_inverter_schematic.jpeg |
| 151 :class: image-process-large-photo | 151 :class: image-process-large-photo |
| 152 | 152 |
| 153 Looking at the schematics and the boards, I did find several failure points: | 153 Looking at the schematics and the boards, I did find several failure points: |
| 154 | 154 |
| 155 - one of the 2 150µH inductors on the 160VDC rails (L6 anf L7 on A7A3) ) looked | 155 - one of the 2 150µH inductors on the 160VDC rails (L6 anf L7 on A7A3) ) looked |
| 159 replaced it with a brand new inductor I recently bought when I repaired an | 159 replaced it with a brand new inductor I recently bought when I repaired an |
| 160 old analog scope (Metrix OX734) for a friend of mine (I allways buy several | 160 old analog scope (Metrix OX734) for a friend of mine (I allways buy several |
| 161 more parts than I really need, when these are cheap, just in case; seems to | 161 more parts than I really need, when these are cheap, just in case; seems to |
| 162 be a good idea), | 162 be a good idea), |
| 163 | 163 |
| 164 .. image:: {filename}images/hp8662a/broken_choke.jpg | 164 .. image:: {static}/images/hp8662a/broken_choke.jpg |
| 165 :class: image-process-large-photo | 165 :class: image-process-large-photo |
| 166 | 166 |
| 167 .. image:: {filename}images/hp8662a/replacement_choke.jpg | 167 .. image:: {static}/images/hp8662a/replacement_choke.jpg |
| 168 :class: image-process-large-photo | 168 :class: image-process-large-photo |
| 169 | 169 |
| 170 - there are 2 small 400mA fuses on the inverter board to protect the base of | 170 - there are 2 small 400mA fuses on the inverter board to protect the base of |
| 171 the 2 switching (bipolar!) transistors (first time I see the base of an NPN | 171 the 2 switching (bipolar!) transistors (first time I see the base of an NPN |
| 172 transistor protected by a fuse, but it's also the first time I repair a | 172 transistor protected by a fuse, but it's also the first time I repair a |
| 174 MOSFET or so). These are small BUSS GMW 4/10 (400mA) fuses, they look nice | 174 MOSFET or so). These are small BUSS GMW 4/10 (400mA) fuses, they look nice |
| 175 and so but are very expensive (and a bit hard to find): something like 15€ | 175 and so but are very expensive (and a bit hard to find): something like 15€ |
| 176 each. So for now, I've replaced it with a simple 5x20 glass fuse: not as | 176 each. So for now, I've replaced it with a simple 5x20 glass fuse: not as |
| 177 skookum but does the job for a few cents. | 177 skookum but does the job for a few cents. |
| 178 | 178 |
| 179 .. image:: {filename}images/hp8662a/fuse_replacement.jpeg | 179 .. image:: {static}/images/hp8662a/fuse_replacement.jpeg |
| 180 :class: image-process-large-photo | 180 :class: image-process-large-photo |
| 181 | 181 |
| 182 | 182 |
| 183 After these fixes, I reassembled the PSU and tried again: the result was quite | 183 After these fixes, I reassembled the PSU and tried again: the result was quite |
| 184 promising, but not a complete success: the PSU seemed to start, but very | 184 promising, but not a complete success: the PSU seemed to start, but very |
