Sadly, I decided to present the 2020B with a 0.5 A load and the voltage dropped significantly. The current limit knob is set to its maximum position (i.e., turned all the way clockwise), so I am not being current limited. Also, the voltage range lamp doesn't flash to indicate that current limiting in effect. It is just misregulating.
At a 5 V, almost perfect setting with no load, I am only getting 4.319 V into the 10 ohm resistive load. I removed the bottom panel and noticed that there are three additional trim pots on the main board. Trim pot R8 controls the maximum current output. I have adjusted it for a 2.1 A output using a setting of 5 V, as instructed in the manual. Trimmer pot R104 is a mystery - I have no idea what it does and its function is not stated on the circuit diagram in the Operating Guide.
At larger voltages, such as 15 V, I am getting a drop of something like a volt and a half into a 1.5 A load (this time), again without any sort of current limiting kicking in.
Also, I noticed that the label above the current knob says, "Pull to set." However, the current limit can be adjusted without pulling the knob (tested with both an ammeter connected directly to the DC-/DC+ terminals and with a load present combined with an ammeter in series). What is even weirder is that if I do pull out the Current adjustment knob all that happens is that the current is limited to half of the available current range (i.e., instead of a 0-2 A adjustment, it becomes approx. a 0-1 A adjustment) further reducing the current output capability of the device while the knob remains pulled out. It doesn't make any sense to me. How the heck is this knob supposed to function when it's pulled out vs. pushed in?
Here is a high quality high resolution picture of the front of the 2020B's main circuit board (To see it in full resolution, click on the image and then click again on the resulting image in your browser to zoom in to 100%):
I would like to get the supply's load voltage to match its no load voltage, so any help would be appreciated. Maybe
U1b (current limiting amplifier) is bad, but if that was the case, why is the voltage into no load almost spot on? The shape and color of R38 is suspicious, I will measure it to see if it's good.
Update: I thought that R38 (the resistor that looks like a burned marshmallow under the topmost blue trimmer pot) looked a bit weird, but it checks out fine at its rated 0.15 Ohms.