DL3021 to DL3031 Conversion Discussion

[Pedrofabian]

Hi all,
so recently I've come in possession of a Rigol DL3031 350W E-Load with a broken screen. I already had a working DL3021, so naturally I swapped it's screen to the higher end model.

Sidenote: I did go back and replace the screen on the DL3021 for anyone interested. It's an LCD with a glass/plastic cover. LCD part number is TM043NBH02. There was no finding an original piece of cover glass, but I did fine a Glass resistive touch screen digitizer of the same dimensions (105x65mm) which fit perfectly, looks like new!

Upon opening up the DL3031, I was surprised to find that it appeared to have no more MOSFets or other parts that the DL3021. In part, this made some sense, as the insides of the DL3021 are far too robust for a 200W load. The MOSFets are all in the same place and have the same part number.

I've already flashed the DL3031 to the DL3031A and the DL3021 to a DL3021A using the method outlined here
https://www.eevblog.com/forum/testgear/need-help-hacking-dp832-for-multicolour-option/

Naturally the question comes up, can you turn the DL3021 into a DL3031?
As it appears to me, the only distinction between a 3021 and a 3031 might be firmware.

Sanity check before I burn my perfectly good DL3021? Pictures attached.
DL3021: https://imgur.com/a/Kjg2z5o
DL3031: https://imgur.com/a/OFUONn9

[electr_peter]

Conversion to *A models has been done with no negative effects, 21->31 conversion would be welcome
Also, it would be great to know if the same method via SCPI could work for this hack.

Just be 100% sure before any changes - are you certain that DL3031 unit was DL3031 from the factory? If so, this makes whole DL3000 range (DL3021/3021A/3031/3031A) differs only in FW and front panel markings. Current idea is that DL3031 has more stuff in it, but that could be a myth.

Images in your links look very similar (you can attach pictures on forum post as well). I can't see all the details, but shunt looks the same, power MOSFETs seem the same, circuitry around is the same..., i.e., looks very promising.

Now, as you have both DL3021 and DL3031, can you test few identical load scenarios on both loads? Say, one at 200W, one at 40A. Look for heat dissipation, try measuring control voltages.

[electr_peter]

Specs suggests no or almost no HW differences between DL3021A and DL3031A, as models differ only in:

• Maximum Power - 200W vs 350W
• Minimum Operating Voltage - 40A @ 1V vs 60A @ 1.3V (0.025 vs 0.022 estimated R_DS_ON)
• Current Slew Rate - 0.001 A/μs~0.3 A/μs vs 0.001 A/μs~0.5 A/μs
• Current Slew Rate - 0.001 A/μs~3 A/μs (>5 V) vs 0.001 A/μs~5 A/μs (>5 V)

Max power is SW limit; internal resistance is almost the same. Current slew rate is slightly faster, but it is explainable by different max current. From specs:

Current slew rate: rising slew rate for 10%~90% of the current (0-maximum current).

Firmware file is the same for all models of DL3000 range.
Looks even more promising

[Pedrofabian]

Yes I know I can upload pictures but it was too many, it exceed the size limit

Yes this is an original DL3031 (non A version)
I have the test running now. Will allow to run for a little while before checking heat and some voltages.

[Pedrofabian]

Ran both units at 200W for about 30 minutes
They both stabilized similarly to ~40C
I measured the voltages across most of the MOSFETs (the ones I could reach) and they are all biased with similar voltages.
Not super sure what else to check? Next steps or YOLO?

[Pedrofabian]

Hello. I'm impatient!
SO I went ahead and flashed the DL3021 to DL3031A
Here are the results and some notes:
1. Before flashing, I went ahead an loaded the DL3031(A) at 350W, specifically ~14V at ~24.5A for ~1 hour. It got pretty hot, but the temperature stabilized around 49.5C
2. I flashed the DL3021 to a DL3031A using the same method mentioned in the post. Sidenote: Apparently, you can set anything to the model number. I accidentally set the model number to DL3001A and it took it, it updated the system menu, but all the features reverted to the 3021 set and limits.
3. Once flashed, everything appeared nominal except for one bug, I could not set the current limit in CC mode while in the 60A range. I could set all the other limits in that mode and all the other modes. Neither the number pad or knob worked. Only way to circumvent was to go into the factory test mode and set it there. Returning to CC mode would have the updated limit. However this went away after leaving it loaded for 1 hour.
4. I left the DL3021 (31A) loaded at 350W, same as before ~14V at ~24.5A for ~1 hour. It got hot like the DL3031(A) and the temperature stabilized around 51.8C.

So overall a success.
I don't really have the means (Well not without a lot of effort on my part) to check the behavior at the limits, 5.8V at 60A, 150V at 2.3A.

[electr_peter]

Ran both units at 200W for about 30 minutes. They both stabilized similarly to ~40C

1. Before flashing, I went ahead an loaded the DL3031(A) at 350W, specifically ~14V at ~24.5A for ~1 hour. It got pretty hot, but the temperature stabilized around 49.5C
4. I left the DL3021 (31A) loaded at 350W, same as before ~14V at ~24.5A for ~1 hour. It got hot like the DL3031(A) and the temperature stabilized around 51.8C.

Cooling performance is identical (same size heatsink, same fan) and adequate for 350W.

2. I flashed the DL3021 to a DL3031A using the same method mentioned in the post.

Easy mod. USB connection with Rigol Ultra Sigma SW can be used to issue SCPI command.

3. Once flashed, everything appeared nominal except for one bug, I could not set the current limit in CC mode while in the 60A range. I could set all the other limits in that mode and all the other modes. Neither the number pad or knob worked. Only way to circumvent was to go into the factory test mode and set it there. Returning to CC mode would have the updated limit. However this went away after leaving it loaded for 1 hour.

Can you confirm that this bug disappeared after restart? Also, what CC ranges (4/40A in DL3021) and max limits (70A max in DL3021) do you see in CC settings menu?

I don't really have the means (Well not without a lot of effort on my part) to check the behavior at the limits, 5.8V at 60A, 150V at 2.3A.

Be careful with 150V, it can damage the instrument. I have access to 60A capable supply and DL3021(A), I will have to ask.

[Pedrofabian]

OK
So no the bug didn't go away, it reappeared after restart. It's easy enough to circumvent with the factory test mode but annoying since it's the only tiny flaw. I'm going to try to re-flash firmware. Maybe something went wrong when I entered the wrong model number during the 3021 -> 3031A conversion.

Yes, everything is as you'd expect from the 3031A, 6A/60A ranges, 155 V-Limit, 70A C-Limit

I decided to be thorough and conducted a last test @60A. I scrounged up every last power supply and 5V power adapter and threw them in parallel. Managed to just scrape 60A @ 5V = 300W, though its pretty sketchy, had to actively cool my banana <-> spade converters.
Before I tested with the cover off, but this time taped my thermistor inside and ran the wires out of the cover, just to be extra thorough, so its completely nominal conditions. I ran the test for 60 minutes.
It rose to 63C pretty quickly, in around 15 minutes, and then stayed there. Well within the operating range of anything inside.

I'm going to call this good. Congrats to all 3021 owners, and my apologies for those who payed $1000 for the 3031.

[Pedrofabian]

About the bug I mentioned.
The bug is this specifically: the unit starts up in CC mode with a current limit of 40A in the 60A range. Then you cant change the current limit, only if you switch to the 6A range. Normally when you start the unit you start with a 0A limit in the 6A range.
So I reflashed the firmware, which fixed it after 1 reset, but further resets presented the same problem. Somethings the issue would go away after fiddling with the range and 6A range current limit.
I then went into utilities and reset the configuration which seems to have fixed the issue. 10 resets and counting.

[idolclub]

After change to DL3031A, just do a Reset to defaults in Utiltity Menu once and Power Off, that's all.

[electr_peter]

Successful conversion to DL3031A. Model number is shown as DL3031A, no bugs were noticed (did system reset before & after mod). Tested with 350W and 60A loads, all is fine. Thanks to @Pedrofabian for confirmation that hardware is the same for all DL3000 range

To anyone interested in how to do the mod between RIGOL DL3021/3021A/3031/3031A models:

• turn on DL3000 load, make a system reset via menu, stick in prepared USB stick
• connect to DL3000 and open SCPI/serial terminal: via USB (Rigol Ultra Sigma or serial terminal) or via RS232(Rigol Ultra Sigma or serial terminal) or via LXI LAN (telnet or RigolBildschirmkopie)
• enter command "*IDN?" (without quotes, should show current model number - if not, something went wrong in step #2)
• enter command ":PROJ:SET MODEL,DL3031A" (without quotes, model number is from a set {DL3021/DL3021A/DL3031/DL3031A})
• enter command "*IDN?" (without quotes, should show new model number - if not, something went wrong with step #1 or #4)
• restart device, make a system reset
• enjoy

[tv84]

What about DL3051?

[thm_w]

What about DL3051?

Yeah someone please test.
There are 10 FETs installed, and then 6 empty positions available. So this would imply original spec of 300W, with all 16 FETs = 480W, close enough.

IRFP250 is easy enough to purchase, not sure about the opamp and other passive components. and if a recal is necessary. Or if they simply operate all these FET drive circuits in parallel, then maybe installing more has no effect on the software, its just a simply watt limit.

[electr_peter]

What about DL3051?

Tested DL3051A option. Model number changes (*IDN? -> RIGOL TECHNOLOGIES,DL3051A,DL...........,00.01.05.00.01)
On boot it shows error "Self-test error for OCP reference voltag" (after canceling error doesn't reappear until next boot).
Current ranges changed to 9/90A (compared to 4/40A or 6/60A), but max current limit remains unchanged at 70A (same as for DL3021/3031).
Max power setting increases to 500W (compared to 200 or 350W).
Other than that, seems to work, accuracy and functions remain unchanged.

So full mod to 150V/90A/500W DL3051A would require some work with FW (OCP reference?, max current limit) and HW (MOSFETs and driving circuitry).

[Wintel]

What about DL3051?

Tested DL3051A option. Model number changes (*IDN? -> RIGOL TECHNOLOGIES,DL3051A,DL...........,00.01.05.00.01)
On boot it shows error "Self-test error for OCP reference voltag" (after canceling error doesn't reappear until next boot).
Current ranges changed to 9/90A (compared to 4/40A or 6/60A), but max current limit remains unchanged at 70A (same as for DL3021/3031).
Max power setting increases to 500W (compared to 200 or 350W).
Other than that, seems to work, accuracy and functions remain unchanged.

So full mod to 150V/90A/500W DL3051A would require some work with FW (OCP reference?, max current limit) and HW (MOSFETs and driving circuitry).

Can you get over 200W in CR mode with flashed DL3021 to DL3031A?

[Pedrofabian]

Installing the missing MOSFETs and control circuitry seems pretty involved but fairly easy.

Now if only we had calibration documentation for these loads.

[Pedrofabian]

What about DL3051?

Tested DL3051A option. Model number changes (*IDN? -> RIGOL TECHNOLOGIES,DL3051A,DL...........,00.01.05.00.01)
On boot it shows error "Self-test error for OCP reference voltag" (after canceling error doesn't reappear until next boot).
Current ranges changed to 9/90A (compared to 4/40A or 6/60A), but max current limit remains unchanged at 70A (same as for DL3021/3031).

Max power setting increases to 500W (compared to 200 or 350W).
Other than that, seems to work, accuracy and functions remain unchanged.

So full mod to 150V/90A/500W DL3051A would require some work with FW (OCP reference?, max current limit) and HW (MOSFETs and driving circuitry).

Did you try resetting the settings again after changing the model? Maybe that would fix the max current limit issue

[tv84]

Tested DL3051A option. Model number changes (*IDN? -> RIGOL TECHNOLOGIES,DL3051A,DL...........,00.01.05.00.01)
On boot it shows error "Self-test error for OCP reference voltag" (after canceling error doesn't reappear until next boot).
Current ranges changed to 9/90A (compared to 4/40A or 6/60A), but max current limit remains unchanged at 70A (same as for DL3021/3031).
Max power setting increases to 500W (compared to 200 or 350W).
Other than that, seems to work, accuracy and functions remain unchanged.

So full mod to 150V/90A/500W DL3051A would require some work with FW (OCP reference?, max current limit) and HW (MOSFETs and driving circuitry).

   Thanks for testing!

[electr_peter]

Can you get over 200W in CR mode with flashed DL3021 to DL3031A?

Modded DL3031A can get over 200W in CR mode. Keep in mind that in lower 0.08 Ohm ~ 15 Ohm range voltage is limited to 8V (beeps and stops otherwise). Higher range (2 Ohm ~ 15 kOhm) does not have voltage limit.

[electr_peter]

Did you try resetting the settings again after changing the model? Maybe that would fix the max current limit issue

Reset did not help, limit seems to be hardcoded in FW. Same 70A limit was available for 40/60A versions (i.e. no overlimit under normal conditions).

[electr_peter]

Comment from EEVblog #1023 - Rigol DL3021 Electronic Load Teardown confirming same HW in DL3021/DL3031.

My company uses a Rigol DL3031 load. I took it apart and looked at it too. It is no different from Rigol DL3021. MOSFET quantity 10 pcs. The same IRFP250N. Maximum current limitation is performed by the program. These transistors are controlled by the MC33078 chip without marking. The shunt has a resistance of 0.0005 ohms. From this shunt amplifies the signal, the ADA4522-1 chip is unmarked. Still without marking, 3 chip OP27G. I haven't identified the DAC chip yet. If anyone knows what it's called, write.

[ben_r_]

This is great news! Saved me $700USD by not having to buy the DL3031A! Thank you all for your fearless testing! 

[probe]

Another successful conversion from a DL3021 to a DL3031A! Embarrassingly enough I wasn't able to connect to it through USB on a Linux machine, neither Kali on a RPi4 or Ubuntu in a VM (MacOS Ventura as a host), all I got was "access denied". I had to install UltraSigma on a Windows 10 machine and the moment I sent the SCPI command the screen on the load turned to the color interface. No issues after a reboot and it is recognised in LXI-tools when connected via LAN. Unfortunately no print screen function available in LXI-tools for this device but all in all happy days.

[Mouse69]

Thanks so much guys, another successful conversion from a DL3021 to a DL3031A.
I used to install UltraSigma on a Windows 11 (please don't judge me) machine, the moment I sent the SCPI command the screen on the load turned to the colour interface 

[ben_r_]

Thanks so much guys, another successful conversion from a DL3021 to a DL3031A.
I used to install UltraSigma on a Windows 11 (please don't judge me) machine, the moment I sent the SCPI command the screen on the load turned to the colour interface 

Just double checking, what firmware version were you running? It looks like the latest is: 00.01.05.00.01