You have more than one output?

Connect the positive of one output to the negative of another output, call this ground (or 0 volts).

The un-connected positive terminal is now + volts, and the un-connected negative terminal is now - volts.

o o---o o
-ve Gnd +ve

 

ya, I just did this and finally was able to get a -ve voltage.

Now I assume this requires that both channels be set to the same voltage or it'll be unbalanced.

Is that ground truly 0V though?

 

Balanced?

Truly 0V?

Ask yourself this What is voltage? (or more correctly what is ground)

 

ground is the 0V reference, it carries the unbalanced portion of a load to ground (or am I getting confused with AC and common)

but if channel 1 was set to 5V and channel 2 was set to 10V, sure my output reading would be 15V across both, but between ground there is an unbalance where one rail is 10V and the other is 5V

 

I just realized that running it in series mode adjusts both channels with the master adjustment.

There is some slight variance though, like at maximum voltage channel 1 is 30.9V and channel 2 is 31.5V

It's not a huge difference but I'm sure somewhere on this PSU are some trim pots to adjust the output ranges.

 

Have you measured the output voltages or are you assuming the LED/LCD display is correct?

 

I've measured, and get some differences I'd consider significant, but I'm not sure if it's my meter that's on it's way out, or if the PSU is that far out.

yesterday I had it set to 5V and was measuring 5.4, so I turned it down until my meter read 5V and then the PSU said 4.6.

 

I'd bet that the meter was correct.....

There should be a pot on the display board that you can tweak....

HTH Steve.

 

I'd bet that the meter was correct.....

There should be a pot on the display board that you can tweak....

HTH Steve.

Yeah I've seen those. So would they adjust the output? or are they basically just there to adjust the displays to the correct reading?


On the actual power supply/relay boards there is a pot, but I don't know what it does.

 

Correct the displays first, so that they show the actual voltage output as measured.

Then maybe post a schematic of the power supply, and we'll see what the other pot does....

 

Here is the only schematic available for this unit, and it isn't the exact unit.

 

The trimpot on the display board is to calibrate the display. It does not affect the PSU output.

Adjust the trimpot to match the PSU display with your DMM display.

 

that's what I figured, I wonder if there is a way to adjust the actual output. Once I calibrate the displays, then it may not reach 30V on the upper end.

 

I see three trimpots on the PSU schematic. One of them is to adjust the max range of the PSU voltage output. At this point I would have to analyze the circuit in order to tell you which one to adjust.

 

this is one of the power supply boards. There are two pots on it. and I think this is the only other place there are any pots.