EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: JacquesBBB on October 12, 2014, 02:24:42 pm
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Dear all,
I get hold on a 30 V 3A dual bench power supply Selectronic SL-1731SB, which seems to be the same
as the Velleman PS23023, and maybe some other ones.
Both canals are OK, but when I coupled them in series, the coupling is totally wrong
example
Tracking not activated : A : 5.4 V B: 10.3 V (photo 2)
Tracking activated : A :25 V B : 10.3 V (photo 3)
While one would expect to see both channels at 10.3V
I could find a schematic of the PS23023 on the web
https://www.velleman.eu/downloads/2/ps23023gbnlfresd.pdf (https://www.velleman.eu/downloads/2/ps23023gbnlfresd.pdf)
But I cannot locate the place I should look for some faulty component.
In the power supply, apart from the display section,
there are two same boards for each channel, an additional board for
the 5V channel, and a small board with lots of diodes that
I do not identify the role. (photo 1)
Can anybody help me, by telling me where to search for
the faulty tracking behavior ?
Thanks
jxlbbb
(http://)
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Are you sure that the Vellerman manual corresponds to your power supply? The manual indicates two power transformers; I can only see one in the photo!
The small board with diodes is possibly providing floating power supplies for the four panel meters.
In independent mode, do the two channels function properly through their entire range? If they do, I would strongly suspect poor contacts on the two push buttons. Try exercising the push buttons and/or some contact cleaner.
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Thanks Andy,
Are you sure that the Vellerman manual corresponds to your power supply? The manual indicates two power transformers; I can only see one in the photo!
The photo is a partial view. There is a second transformer. I have also added a photo of the main board where the components can be easily identified. There is no doubt the power supply is the same as in the schematics of Velleman PS23023.
The small board with diodes is possibly providing floating power supplies for the four panel meters.
Thanks, I checked a few components there and everything seems OK.
In independent mode, do the two channels function properly through their entire range? If they do, I would strongly suspect poor contacts on the two push buttons. Try exercising the push buttons and/or some contact cleaner.
Yes, the two channels were OK over the whole range. I tested them with a 22 ohm load and a multimeter.
I will test the push button. Thanks for the hint !
Jacques
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Bingo !
Andy, you were right !
I measured the resistors at the pins of the push button. It was well conducting when closed,
but seems to be problems for the open state. I dried everything with the hair dryer,
fiddle a little bit with it, and then it went right in the proper state. The slave now follows the
master properly within 0.1 V. Maybe it remains to do a little bit of tuning.
Does anybody know the proper sequence for tuning the RP1, RP2, and RP9 pots on the board of
this power supply, following the schematics of the PS23023.
https://www.velleman.eu/downloads/2/ps23023gbnlfresd.pdf (https://www.velleman.eu/downloads/2/ps23023gbnlfresd.pdf)
Thanks
Jacques
PS : The answer to the latest question has been given in the following thread
https://www.eevblog.com/forum/repair/tuning-a-ps23023-power-supply/ (https://www.eevblog.com/forum/repair/tuning-a-ps23023-power-supply/)