Short quick review - TENMA 72-7245 bench PSU

[Tony.]

Just picked up one of these:

http://www.newark.com/tenma/72-7245/power-supply-bench-30v-60v/dp/22H6396

BUT.... I did not buy it there. I was able to score a new one on eBay for less than $150 shipped to California.
At that price I think it's a pretty sweet deal. It's my first bench PSU.

Pros

2 independent channels 0-30v @3A
series and parallel tracking
Seems to be pretty well built, knobs and switches seem to be pretty good quality.
Selectable mains voltage input
Down to 0A and 0V no prob
Current and Voltage LCDs look great, excellent contrast.
CV, CC green/red LED indicators
Came with 2 pairs of nifty aligator leads

Cons

Only 1 load switch for both channels.
No multi turn pots! Grrr
LCD only has 100mV and 10mA resolution
Have to short output to set current limit

Unfortunately I don't have my Oscope to measure noise and overshoot under load and the like. I'm in the market for a new one of those as well.
Anyways, I like this power supply quite a bit. It wouldn't be great for most EE work. In that case you'd want precision rather than power. But I love the power capabilities. It's great for testing and profiling high power LEDs and laser diodes. I do alot of RC and robotics stuff too so it makes testing motors and servos convenient. Since the LCDs don't offer much resolution you can sort of forgive the lack of 10 turn pots. Shorting the outputs to set the current is annoying, but it's to be expected at this price point. I did have a peek inside, and as far as my first semester EE knowledge goes it looks pretty well designed and laid out. Temp sensors on the semi heatsinks, nice beefy toroidal transformer, lots of open airflow inside, killer fan... I'll rip it apart again and post pictures if enough of you are curious.

Other thoughts
When you turn the load switch off the current LCD drops to zero as you'd expect. But, so does the voltage reading. In fact I was using the PS to charge a li-ion battery and when I shut off the load the display showed the voltage from the battery. In other words if you feed a voltage into the unit with the load switch off the LCD acts like a volt meter. Not sure if thats a good thing or not. I was kinda hoping it would always display the voltage setting even when the output was off.

Tenma seems to be highend low range or mid range quality stuff.
I hope it lasts a long time.

[c4757p]

The voltmeter thing is common in cheaper power supplies. They have to get the reading right off the panel jack so it isn't affected by current losses in the wires, so naturally it is in front of the load switch. The load switch would have to be DPDT and switch the sense line as well. Most of these don't have any sort of microcontroller that can do this intelligently.