comparison: content/LPD422FM.rst
content/LPD422FM.rst
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| 1 ============================= | |
| 2 Lambda LPD 422 FM Bench PSU | |
| 3 ============================= | |
| 4 | |
| 5 :Author: David Douard | |
| 6 :Category: Electronics | |
| 7 :Tags: test equipment, PSU | |
| 8 | |
| 9 This post is a quick presentation and teardown of a small bench power | |
| 10 supply I bought on ebay a few weeks ago for something like 40€. | |
| 11 | |
| 12 .. image:: {filename}/images/lambda/lpd422fm_overall.jpg | |
| 13 :alt: The Lambda LPD 422 FM dual regulated power supply. | |
| 14 | |
| 15 It's an old unit, not sure exactly it's exact age, but the components | |
| 16 inside the unit seem to hase date codes around 1971/1972. So my unit | |
| 17 is probably from the late 1972. (One of the available user manual on | |
| 18 the internet seems to be dated from 1987n but it's for the "A" | |
| 19 version.) | |
| 20 | |
| 21 Overview | |
| 22 ======== | |
| 23 | |
| 24 It's a dual regulated linear power supply which specifications are: | |
| 25 | |
| 26 - voltage range: 0V to 40V | |
| 27 - curent regulation: 0 to 1A current limitation | |
| 28 - voltage regulation: 0.01% + 1mV | |
| 29 - ripple and noise: 500 µVrms, 1.5mVpp | |
| 30 | |
| 31 | |
| 32 It seems to be "remote programmable", and have remote sensor entries | |
| 33 on the back of the unit. | |
| 34 | |
| 35 .. image:: {filename}/images/lambda/lpd422fm_back.jpg | |
| 36 :alt: Rear view of the LPD 422 FM dual regulated power supply. | |
| 37 | |
| 38 Inside the enclosure: | |
| 39 | |
| 40 .. image:: {filename}/images/lambda/lpd422fm_top.jpg | |
| 41 :alt: Top view of the LPD 422 FM dual regulated power supply. | |
| 42 | |
| 43 Each of the 2 power supplies have a regulator board on each side of | |
| 44 the enclosure. The power transformer is sitting at the center of the | |
| 45 enclosure and shows a nice "Component Location Diagram": | |
| 46 | |
| 47 .. image:: {filename}/images/lambda/lpd422fm_xformer.jpg | |
| 48 :alt: The power transformer of the LPD 422 FM dual regulated power supply. | |
| 49 | |
| 50 A regulator board looks like: | |
| 51 | |
| 52 .. image:: {filename}/images/lambda/lpd422fm_board2.jpg | |
| 53 :alt: Top view of one regulator of the LPD 422 FM dual regulated | |
| 54 power supply. | |
| 55 | |
| 56 .. image:: {filename}/images/lambda/lpd422fm_board1.jpg | |
| 57 :alt: Bottom view of one regulator of the LPD 422 FM dual regulated | |
| 58 power supply. | |
| 59 | |
| 60 The component, especially the big caps, looks like original parts and | |
| 61 the PCB is a bit burnt by the small power transistor, but nothing too | |
| 62 scary. | |
| 63 | |
| 64 The power supply works nice. No smoky or smelly behaviour on load, and | |
| 65 the regulation looks still reasonnable. | |
| 66 | |
| 67 | |
| 68 Available documentations | |
| 69 ======================== | |
| 70 | |
| 71 - `Lambda LP, LPD & LPT series catalog | |
| 72 <{filename}/pdfs/lambda/LAMBDA_LPD_LPD_LPT_series.pdf>`_ | |
| 73 | |
| 74 - `Instruction and Service Manual for Lambda LPD suffix A Series Power | |
| 75 Supplies <{filename}/pdfs/lambda/LambdaLPD.pdf>`_: this is not | |
| 76 exactly the same model, but it really very close. | |
| 77 | |
| 78 | |
| 79 | |
| 80 Quick mesurements | |
| 81 ================= | |
| 82 | |
| 83 In these quick measurements, I've not used the voltage remote sensing | |
| 84 of the power supply. | |
| 85 | |
| 86 First, a view of the noise at the output of the PSU; 0V, no load: | |
| 87 | |
| 88 .. image:: {filename}/images/lambda/DS1Z_QuickPrint2.png | |
| 89 :alt: Noise level of the LPD422FM - 0V/0A | |
| 90 | |
| 91 Same at 20V, no load: | |
| 92 | |
| 93 .. image:: {filename}/images/lambda/DS1Z_QuickPrint3.png | |
| 94 :alt: Noise level of the LPD422FM - 20V/0A | |
| 95 | |
| 96 And at maximum voltage (40V, no load): | |
| 97 | |
| 98 .. image:: {filename}/images/lambda/DS1Z_QuickPrint4.png | |
| 99 :alt: Noise level of the LPD422FM - 40V/0A | |
| 100 | |
| 101 Then, with the `ZPB30A1 electronic load <{filename}/ZPB30A1.rst>` | |
| 102 connected but not consuming any current (20V, 0A): | |
| 103 | |
| 104 .. image:: {filename}/images/lambda/DS1Z_QuickPrint5.png | |
| 105 :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0A | |
| 106 | |
| 107 As you can see, there is a much higher injected by the electronic | |
| 108 load. When measuring the visible pattern: | |
| 109 | |
| 110 .. image:: {filename}/images/lambda/DS1Z_QuickPrint6.png | |
| 111 :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0A | |
| 112 | |
| 113 it's a 20ms pattern, ie. it's the mains 50Hz being injected... Let's | |
| 114 turn the load on (20V, 0.5A): | |
| 115 | |
| 116 .. image:: {filename}/images/lambda/DS1Z_QuickPrint7.png | |
| 117 :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0.5A | |
| 118 | |
| 119 The injected noise from the mains has vanished, and the RMS noise | |
| 120 level is back to the same value as it ws with no load (around 40mV). | |
| 121 | |
| 122 At 1 amp, it's roughly the same: | |
| 123 | |
| 124 .. image:: {filename}/images/lambda/DS1Z_QuickPrint8.png | |
| 125 :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/1A | |
| 126 | |
| 127 Now, trying to capture the transient curve when activating and | |
| 128 deactivating the load. As I cannot remote control the load, I cannot | |
| 129 create a nice square load pattern which make this measurement much | |
| 130 easier. So I've just adjusted the trigger level to single capture the | |
| 131 moment I press the 'on/off' button of the load: | |
| 132 | |
| 133 .. image:: {filename}/images/lambda/DS1Z_QuickPrint10.png | |
| 134 :alt: Transient response of the LPD422FM connected to the ZPB30A1 - 20V/1A -> 0A | |
| 135 | |
| 136 .. image:: {filename}/images/lambda/DS1Z_QuickPrint11.png | |
| 137 :alt: Transient response of the LPD422FM connected to the ZPB30A1 - 20V/0A -> 1A | |
| 138 | |
| 139 The overshoot is around 75mV and takes around 200ms to vanish, and the | |
| 140 undershoot is a bit less (50mV) and lasts 150ms. | |
| 141 | |
| 142 At one amp, the ripple voltage is around 8mVpp and 3mVrms: | |
| 143 | |
| 144 .. image:: {filename}/images/lambda/DS1Z_QuickPrint13.png | |
| 145 :alt: Ripple voltage of the LPD422FM connected to the ZPB30A1 - 20V/1A | |
| 146 | |
| 147 It's quite out of spec: ripple should be less than 500µVrms and | |
| 148 1.5mVpp, but it's not really a surprise considering the age (over 40 | |
| 149 years old!) of the PSU. A future recap may improve its performances to | |
| 150 its original specifictions. | |
| 151 | |
| 152 |
