ACME PS2L-1000 - 1000W Electronic Load Teardown

[Jay_Diddy_B]

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 Max

This 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.

Manual

The manual can be found here:

http://userequip.com/files/specs/3577/ACME%20PS2L-500,%20PS2L-1000%20Operating%20&%20Troubleshooting%20Guide.pdf

The manual contains partial schematics.

Pictures




The leads are long enough to allow the front panel to be laid down.






This shows the back of the front panel.

Heatsink assembly







The 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 Details

There are nine T0-3 transistor on each heatsink:




The transistors are mounted in sockets. Each transistor has 0.4 emitter 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 Board

Here is a picture of the control board. It is a single sided board. I will replace the electrolytic capacitors.




Regards,
Jay_Diddy_B

[Jay_Diddy_B]

Hi,

I have replaced the electrolytic capacitors on the control board:





Capacitors used

Code: [Select]

ACME PS2L-1000 Capacitors

Digikey QTY Description MFG MFG No Notes

1572-1126-ND 2 CAP ALUM 330UF 20% 50V AXIAL Illinois Capacitor 337TTA050M
4050PHCT-ND 1 CAP ALUM 150UF 20% 40V AXIAL Vishay Beyschlag/Draloric/BC MAL202137151E3
4023PHCT-ND 1 CAP ALUM 1000UF 20% 16V AXIAL Vishay Beyschlag/Draloric/BC MAL202190518E3 was 820uF
56-MAL203038228E3CT-ND 4 CAP ALUM 2.2UF 63V AXIAL Vishay Beyschlag/Draloric/BC MAL203038228E3


I 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

[bnetz]

Thanks for the great write up! Do you have a working link to the manual? I recently got one and plan on refurbing it