Re: TEK PS 2521


Siggi
 

Hey Michael,

I can’t think of anything common to all three channels other than the
digital logic. What are you using for load? What’s the current limit you
set? Are the current and voltage read back displays accurate?
What happens if you set the current limit at max, and then load the supply
below max current?

The design of the digital control and read back is pretty old school.
There’s a single DAC per channel, and a serial communication protocol to
it. There’s MUXing downstream from the DAC. Read back is by successive
approximation, by comparing the DACs output against measured current or
voltage.
I assume there’s also dedicated read back of CC/CV/OVP, though I haven’t
studied the schematic in that regard.

Siggi

On Tue, Nov 12, 2019 at 18:28 Michael Yellin <michaelhq54@gmail.com> wrote:

Siggi,

Thanks for the response, and the link. Yes, the CC lights when the load is
connected. However, I believe I have properly set the current limits.
From memory, I choose the output I want to adjust, then choose volt set,
and input the voltage I desire and enter. Then press current set, enter
the current I want, and enter. Then enable the outputs. I also would
assume user error, its my go to most of the time. But in this case, I
actually RTFM.

Thanks,
Michael

On Tue, Nov 12, 2019 at 2:12 PM Siggi <siggi@undo.com> wrote:

Hey Michael,

the schematics for the PS2520G/PS2521G recently surfaced. See
http://bama.edebris.com/manuals/tek/ps2520g/.
When your outputs collapse, do you see the CV/CC indicators change? I
wonder if this is - ehem - operator error and you're in fact tripping
over
the previous owner's (inherited) low, low current limit.
I have one of those supplies and I can say that the user interface on
these
power supplies is ... hard to love.

Siggi

On Tue, Nov 12, 2019 at 4:58 PM Michael Yellin <michaelhq54@gmail.com>
wrote:

Hello,

Recently acquired a Tek 2521G, which appears to be in great shape.
Inspected the inside, and nothing jumps off and the caps looks fine.
However, whenever a load is placed on any of the outputs, the voltage
drops. With no load, the voltage is accurate as set, and when a load
is
placed, the amperage is dead on for the setting. But, as mentioned,
as
soon as a load is placed on any of the outputs, the voltage for that
output
drops significantly. I have run through the calibration, with out
fixing
the unit. I plan to do the complete calibration shortly (all outputs
in
order), but am beginning to think it is not a calibration issue. Can
anyone think of what might cause all the outputs to act exactly the
same.
My understanding is that the unit essentially is three separate
"boards"
so I find it strange that all three outputs are behaving the same. I
have
some basic repair skills, and a fair compliment of test equipment. Any
help would be greatly appreciated.

Thanks,
Michael







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