ACME PS2L-1000 - 1000W Electronic Load  Teardown - Page 1
Forum section: electronics / testgear

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 14, 2020, 10:26:52 pm
content: Hi,There is a lot of interest in electronic loads. I am going to share some pictures of an Acme PS2L-1000 load that I was working on.This load is 60V Max, 110A Max, 1kW MaxThis load is about 40 years old, but it shows how the load was constructed. I had the unit apart for cleaning and electrolytic capacitor replacement. The load will work in constant current and / or constant resistance modes.ManualThe manual can be found here:http://userequip.com/files/specs/3577/ACME%20PS2L-500,%20PS2L-1000%20Operating%20&%20Troubleshooting%20Guide.pdfThe manual contains partial schematics.PicturesThe leads are long enough to allow the front panel to be laid down.This shows the back of the front panel.Heatsink assemblyThe heatsink assembly can be removed, for maintenance. The transistors are electrically connected to the heatsink. The heatsink doubles as the positive bus bar.There is a large stud diode and stud SCR. These are for reverse polarity and Over-voltage protection. They will blow the 130A fuse.Transistor DetailsThere are nine T0-3 transistor on each heatsink:The transistors are mounted in sockets. Each transistor has 0.4emitter resistor.There is no shunt. The current is measured by averaging the voltage across all the emitter resistors.There are 34 transistors, that is 1000/34 = 29W per transistor.Control BoardHere is a picture of the control board. It is a single sided board. I will replace the electrolytic capacitors.Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 21, 2020, 02:10:10 am
content: Hi,I have replaced the electrolytic capacitors on the control board:Capacitors usedCode:ACME PS2L-1000 CapacitorsDigikeyQTYDescriptionMFGMFG NoNotes1572-1126-ND2CAP ALUM 330UF 20% 50V AXIALIllinois Capacitor337TTA050M4050PHCT-ND1CAP ALUM 150UF 20% 40V AXIALVishay Beyschlag/Draloric/BCMAL202137151E34023PHCT-ND1CAP ALUM 1000UF 20% 16V AXIALVishay Beyschlag/Draloric/BCMAL202190518E3was 820uF56-MAL203038228E3CT-ND4CAP ALUM 2.2UF 63V AXIALVishay Beyschlag/Draloric/BCMAL203038228E3I did my best to match the sizes of the originals. It some cases it meant that I had to go to a higher voltage.Regards,Jay_Diddy_B

author: bnetz
author_rank: Newbie
timestamp: April 24, 2024, 08:01:17 pm
content: Thanks for the great write up! Do you have a working link to the manual? I recently got one and plan on refurbing it

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 25, 2024, 01:18:56 pm
content: One maybe stupid question about big electronic loads: Why does it seem all commercial electronic loads use power transistors to dissipate everything?In DIY-loads I usually diverted a DC-DC converter from its original use by modification of the control loop. In the end I had a DC-DC-converter that "sends" a controllable amount of power to an external dissipation device like a water kettle or incadescent lamp.By this setup, you only need a high quality heatsink for the switching losses of the converter - the major part of the load power can be wasted in a part that can be much hotter or is easier to cool by e.g. boiling water. Sometimes I even used an e-bike battery as a "waste device" so that in the end the energy was not lost at all.Maybe you could even connect a micro inverter like it´s used for small domestic PV-generators and recycle the power to the AC-grid.PS: A little googling showed that many larger scale battery test loads nowadays backfeed into mains. Would have been to strange if no one else would have had this idea