Rusty Chroma 6334 DC Load power mainframe

For modern power solutions and automated testing Taiwanese manufacturer Chroma is a well known and recognized brand. I’ve used 6314A mainframe with modules for many years back at EVGA to verify stability of DC-DC converters and power supplies. Now it’s time to repeat the tradition and establish similar 6334 DC load unit at

Enjoy the teardown and some quick test results.

It has seen better days with steel frame parts rusted by the corners and on outer surfaces. All boards are reasonably clean, so it was not a flood or water damage, perhaps just high humidity storage.

Whole battery of good quality Chemi-con capacitors is used to regulate isolated DC output rails for each of the 8 slots that mainframe can accept. It is important for isolated operation per each module. I expect there are multiple transformers under the board with caps (hinted by same battery of diode rectifiers and weight of the side) but didn’t take it apart further to confirm. It would be bit of a challenge with all the cables and wires.

Mainframe alone without any modules draws about 30W from mains power (120VAC 60Hz).

Power draw from mains for the full mainframe with four 63303 modules goes up to around 92-100W.


Modules I got are single-channel only but hardware design on control PCB actually have layout designed for both channels. This module have same feature set as 63103:

  • Constant current (CC), constant resistance (CR) and constant voltage (CV) operation modes.
  • Programmable slew rate, load levels, load periods and conduct voltage (Von).
  • Programmable dynamic loading with speed up to 20KHz.
  • Minimum input resistance allows load to sink high current even with low input voltage (1 V).
  • Selective voltage and current ranges.
  • Remote sensing capability.
  • 100 sets of memories to save/recall user-definable setups.
  • 10 sets of programs to link files for automatic test.
  • 15-bit A/D converter with precision measurement.
  • Short circuit simulation.
  • Automatic GO/NG inspection to confirm UUT within spec.
  • Independent GO/NG signals for each channel
  • The typical temperature coefficient is 100 ppm.

Particular module 63303A have single channel with maximum current 60A, power up to 300W and load voltage from 1V to 80V. Resolution for current setting is 15mA in high-current mode, or 1.5mA in low current mode, with 0.1% accuracy. Current slew rate is programmable from 10mA to 2.5A/µs

Module size is 81 × 172 × 495mm (WxHxD) with 4.2kg of weight.

This 63303 module from year 2007 is older to 63103A dated 2011 year and has some minor component changes. Overall design and specifications in series are identical.

One of great things that this Chroma DC load can achieve is high current loading capability at very low voltages, like shown in test photo below:

25 A can be drawn from power supply at just 0.73 VDC. Perfect for high-current low-voltage regulators verifications, common with FPGA, modern SOC and ASIC products.

Stay tuned and let us know your feedback on this post! Discussion about this and related stuff is also welcome in comment section or at our own IRC chat server: (port six-zero-ten-zero, channel: or via e-mail.

Author: Ilya Tsemenko
Created: Nov. 22, 2023, 7:57 a.m.
Modified: Dec. 10, 2023, 10:25 p.m.