East Tester ET5411 cheap programmable 500V DC electronic load

[duckduck]

East Tester sells cheap (~USD220 delivered to USA) programmable DC electronic loads. The ET5411 is their high-voltage model (500V max). I bought it to test out vacuum tube guitar amplifier power supplies, also USB chargers, wall warts, etc.

The screen is bright and clear but the fonts are unnecessarily small. The user interface is clunky.

The fan runs on low (pretty bearable sound level) until you hit 90W and then it runs on high (loud) until a minute or so after you drop below some threshold (maybe 90W?).

Build quality is pretty cheap, and like all cheap test equipment, you should take it apart before you turn it on to make sure there are no loose pieces and that all of the power lines go to the right places and the grounds are good. The grounds go from the IEC plug to the chassis/tranny frame and then from the other side of the tranny frame up to the top power-MOSFET PCB. Well, the connections were not good because from the ground line on the IEC plug to where the ground connects to the top PCB there was 6 kOhm. I think the issue is the thick clear lacquer on the tranny frame and, ultimately,  (for you "five whys" / Kaizen / lean / Six Sigma fans) a lack of concern by the manufacturer. I replaced the M4 screws and nuts with better hardware and several interior-toothed lock washers to bite through the lacquer / powder coat. I measured again and the PCB ground line to IEC plug resistance dropped to 0.1 Ohms. I could have sworn that I measured input-level DC on the main heat sink (relative to earth ground) before I fixed the ground connections, but I couldn't get even one volt afterwards.

The power switch is a real disconnecting switch, and it switches the line (hot) input. Strangely, the fuse is on the neutral, so after blowing, the unit will still be energized until the power switch is pressed or the IEC cable is disconnected.

My most powerful (working) DC power supply only puts out 60V @ 3A (I've got more broken ones on the way soon).

NOTES:

I used two M4 Kep nuts (use a 7mm wrench), four internally-toothed lock-washers and two M4x12 screws to remount the transformer and chassis grounds.

Firmware: 1.02.2045.030

Front panel PCB is dated 2019.06.21

High V range (the reason why you would buy this model):
   Imax: 3.1A
   Vmax: 510V
   Pmax: 420W

High I range:
   Imax: 16A
   Vmax: 21V
   Pmax: 420W

Fan is blows through heatsink front->back

Heatsinks are isolated from case by thin fiberglass supports in front and a plastic holder in back.

Banana jacks seem very OK.

There is a top PCB with 3 power MOSFETS and a 32-bit ARM, a bottom PCB with 3 power MOSFETS, and the front panel PCB with a 32-bit ARM.

Top and bottom PCBs are mounted to heatsinks with 3mm brass standoffs.

Six IRFPF50 power MOSFETs (3 on top PCB, 3 on bottom PCB). These do not use mica or silpads, just thermal grease.

Displayed amps matches my Fluke 179 very closely at 1A, 2A, and 3A.
Displayed volts matches my Fluke 179 very closely when unit is not sinking power.
Indicated volts drops a little low when sinking power.

PM me if you want me to take more pictures or test anything.

EDIT:

Related ET54xx threads:

https://www.eevblog.com/forum/testgear/et5410-electronic-load-mod-add-external-sense/ (might work for ET5411 as the hardware looks similar)

https://www.eevblog.com/forum/testgear/et5410-or-dcl6104-or-a-third-programmable-electronic-dc-load-in-the-budget-cat/ (posted spec sheet for ET54xx DC electronic loads)

https://www.eevblog.com/forum/testgear/et5410-electronic-load-cccv-and-cccr-modes-what-do-they-do/ (What are CC+CV and CC+CR modes?)

https://www.eevblog.com/forum/testgear/program-that-can-log-from-many-multimeters/ (Datalogging application that might work with ET54xx-series DC electronic loads)

https://www.eevblog.com/forum/testgear/cheap-dc-load/ (discussion about various cheap DC loads)

There are others. Use the search 

[duckduck]

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[duckduck]

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[thm_w]

Unique method of coupling the NTC thermistor.. Probably just bending it over and putting some thermally conductive silicone would work also.

[Hydron]

Thanks for the photos!
Have you done any testing in constant-R mode - is it stable (especially when fed by a switchmode supply)? My DCL6104A (very similar unit, also 500V) is a bit iffy in that situation.

Also, what is it like at low currents? That's the other area where the DCL unit is a little limited (not such a problem for me given I have a SMU as well) - minimum is 10mA, and it has a few mA ripple and offset (ripple much reduced by some mods I made, documented here: https://www.eevblog.com/forum/testgear/et5410-or-dcl6104-or-a-third-programmable-electronic-dc-load-in-the-budget-cat/), but there is still some ripple from the fan magnet spinning next to the current shunt.

[lvictorlucas]

Does anyone have a schematic for the East Tester ET5411 programmable DC electronic load?  My screen does not light up but the fan works when the power button is turned on.  I am hopping the problem is in the power supply circuit.  I have removed the cover but could not find any loose connectors or burned parts.  I hate to scrap it and buy another.  Thank you

[electr_peter]

User interface of ET5411 is disappointing - rotary knob is slow (misses pulses on faster rotation, probably due to insufficient debouncing), screen value update rate is slow, numbers and symbols are super tiny (no way to increase font). Numbers and text on screen seem to be put in row*column matrix with very narrow rows - it is very limiting. Few screens have 2-row*3column format, not easy to interpret. Mode select brings up tiny grey 2-row*5-col table with even smaller font. Number changes are not 100% consistent in different settings, changed decimal is not remembered next time you change the number. Screen real estate is used poorly and it could be improved easily.
Overall, GUI works, but massive improvements could be made with better FW.

There is small enamel mod wire in the middle of ET5411 PCB (top board), it is not visible in OP photos. Could it be improvement or quality control? Need to compare board versions.

Have you done any testing in constant-R mode - is it stable (especially when fed by a switchmode supply)? My DCL6104A (very similar unit, also 500V) is a bit iffy in that situation.

ET5411 seems to oscillate at CR mode, but that depends on attached PSU (PSU control loop has an influence, thus many DC loads can oscillate in specific conditions). Do you have some PSU as reference with setup parameters that creates instability in CR mode?

Also, what is it like at low currents? That's the other area where the DCL unit is a little limited (not such a problem for me given I have a SMU as well) - minimum is 10mA, and it has a few mA ripple and offset

1-2mA and higher seems to be possible in low current range. Current ripple has't been tested yet.

[Swake]

User interface of ET5411 is disappointing
GUI works, but massive improvements could be made with better FW.

That's an understatement... The GUI is ugly, difficult to read and use, non-coherent and unpractical. Same for the buttons, they have bizarre unpractical functionality. It is as if the engineer writing the code never had to use the load.
It is a little frustrating because apart from the worthless GUI it is a good machine for the price. If I had the skills to hack into that stm32f103vct6 arm CPU and write new code for it I would.

[MarkKn]

For my simple needs, it does the job. On CC, the current tracks to my bench meter, the voltage a few percent off.

One specification I am not able to locate is how many volts the negative terminal can be from ground—maybe this is called ground isolation. When using my dmm in dual mode, the ammeter must be in series with the negative leg. Or maybe if I hooked up the dmm with common on the positive side, this would not be a concern. In any case, I like to know this particular spec if anyone knows. I could not find in the manual. thanks

PS. Thinking this through a bit—if the max voltage is 500v, in theory one could set the voltage to 10v with the negative sitting at 490v… If it works that way, meets my needs—but kind of a guess on this scenario.