changeset
[LPD422FM] new blog about the LPD 422 FM regulated power supply
Sun, 17 Apr 2016 18:12:25 +0200
- author
- David Douard <david.douard@logilab.fr>
- date
- Sun, 17 Apr 2016 18:12:25 +0200
- changeset 48
- 0a7b1c6b1796
- parent 47
- c2a88ad9de68
- child 49
- 26e34edd2984
[LPD422FM] new blog about the LPD 422 FM regulated power supply
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/content/LPD422FM.rst Sun Apr 17 18:12:25 2016 +0200 @@ -0,0 +1,152 @@ +============================= + Lambda LPD 422 FM Bench PSU +============================= + +:Author: David Douard +:Category: Electronics +:Tags: test equipment, PSU + +This post is a quick presentation and teardown of a small bench power +supply I bought on ebay a few weeks ago for something like 40€. + +.. image:: {filename}/images/lambda/lpd422fm_overall.jpg + :alt: The Lambda LPD 422 FM dual regulated power supply. + +It's an old unit, not sure exactly it's exact age, but the components +inside the unit seem to hase date codes around 1971/1972. So my unit +is probably from the late 1972. (One of the available user manual on +the internet seems to be dated from 1987n but it's for the "A" +version.) + +Overview +======== + +It's a dual regulated linear power supply which specifications are: + +- voltage range: 0V to 40V +- curent regulation: 0 to 1A current limitation +- voltage regulation: 0.01% + 1mV +- ripple and noise: 500 µVrms, 1.5mVpp + + +It seems to be "remote programmable", and have remote sensor entries +on the back of the unit. + +.. image:: {filename}/images/lambda/lpd422fm_back.jpg + :alt: Rear view of the LPD 422 FM dual regulated power supply. + +Inside the enclosure: + +.. image:: {filename}/images/lambda/lpd422fm_top.jpg + :alt: Top view of the LPD 422 FM dual regulated power supply. + +Each of the 2 power supplies have a regulator board on each side of +the enclosure. The power transformer is sitting at the center of the +enclosure and shows a nice "Component Location Diagram": + +.. image:: {filename}/images/lambda/lpd422fm_xformer.jpg + :alt: The power transformer of the LPD 422 FM dual regulated power supply. + +A regulator board looks like: + +.. image:: {filename}/images/lambda/lpd422fm_board2.jpg + :alt: Top view of one regulator of the LPD 422 FM dual regulated + power supply. + +.. image:: {filename}/images/lambda/lpd422fm_board1.jpg + :alt: Bottom view of one regulator of the LPD 422 FM dual regulated + power supply. + +The component, especially the big caps, looks like original parts and +the PCB is a bit burnt by the small power transistor, but nothing too +scary. + +The power supply works nice. No smoky or smelly behaviour on load, and +the regulation looks still reasonnable. + + +Available documentations +======================== + +- `Lambda LP, LPD & LPT series catalog + <{filename}/pdfs/lambda/LAMBDA_LPD_LPD_LPT_series.pdf>`_ + +- `Instruction and Service Manual for Lambda LPD suffix A Series Power + Supplies <{filename}/pdfs/lambda/LambdaLPD.pdf>`_: this is not + exactly the same model, but it really very close. + + + +Quick mesurements +================= + +In these quick measurements, I've not used the voltage remote sensing +of the power supply. + +First, a view of the noise at the output of the PSU; 0V, no load: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint2.png + :alt: Noise level of the LPD422FM - 0V/0A + +Same at 20V, no load: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint3.png + :alt: Noise level of the LPD422FM - 20V/0A + +And at maximum voltage (40V, no load): + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint4.png + :alt: Noise level of the LPD422FM - 40V/0A + +Then, with the `ZPB30A1 electronic load <{filename}/ZPB30A1.rst>` +connected but not consuming any current (20V, 0A): + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint5.png + :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0A + +As you can see, there is a much higher injected by the electronic +load. When measuring the visible pattern: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint6.png + :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0A + +it's a 20ms pattern, ie. it's the mains 50Hz being injected... Let's +turn the load on (20V, 0.5A): + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint7.png + :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/0.5A + +The injected noise from the mains has vanished, and the RMS noise +level is back to the same value as it ws with no load (around 40mV). + +At 1 amp, it's roughly the same: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint8.png + :alt: Noise level of the LPD422FM connected to the ZPB30A1 - 20V/1A + +Now, trying to capture the transient curve when activating and +deactivating the load. As I cannot remote control the load, I cannot +create a nice square load pattern which make this measurement much +easier. So I've just adjusted the trigger level to single capture the +moment I press the 'on/off' button of the load: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint10.png + :alt: Transient response of the LPD422FM connected to the ZPB30A1 - 20V/1A -> 0A + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint11.png + :alt: Transient response of the LPD422FM connected to the ZPB30A1 - 20V/0A -> 1A + +The overshoot is around 75mV and takes around 200ms to vanish, and the +undershoot is a bit less (50mV) and lasts 150ms. + +At one amp, the ripple voltage is around 8mVpp and 3mVrms: + +.. image:: {filename}/images/lambda/DS1Z_QuickPrint13.png + :alt: Ripple voltage of the LPD422FM connected to the ZPB30A1 - 20V/1A + +It's quite out of spec: ripple should be less than 500µVrms and +1.5mVpp, but it's not really a surprise considering the age (over 40 +years old!) of the PSU. A future recap may improve its performances to +its original specifictions. + +
