Peek Inside These Same-But-Different Power Supplies

When [Kerry Wong] found an Amrel PPS 35-2 Programmable Power Supply from the late 90s on eBay, he recognized it as the single-channel version of another unit he owned, the dual-channel Amrel PPS-2322. Naturally, he purchased it and did a compare and contrast of the two models.

From the outside, they look fairly different but weigh about the same. But the similarities on the inside make it quite clear that they share a common design. There are a few things that grab your eye and the 35-2 doesn’t seem quite as well thought out, with some components being soldered into awkward-looking places. Capacitors bristle like barnacles where they are soldered directly to a connector, and a blob of hot glue anchors two resistors that rise up out of the board like a couple of weeds.

The link above shows some high resolution side-by-side photos between the two models, and [Kerry] thoughtfully provides a link to the manual for the PPS series as well as a dump of the firmware (.zip) for the 35-2. A teardown video is embedded below.

Benchtop power supplies are important tools, but we’ve also seen how modern breadboard power supplies are remarkably full-featured.

5 thoughts on “Peek Inside These Same-But-Different Power Supplies

  1. OK, just saying…
    The title photo showing the power supply and the electronic load misled me into thinking those were the “same-but-different power supplies”.

    I did like the video.

  2. These Amrel (or Motech or Tecpel) supplies are a great value… they’re cheap on the auction sites and it’s pretty simple to hook up a serial to usb adapter to the newer ones (see an example by Matthias over at Sigrok), or just add serial to one that doesn’t have it.

  3. This is nothing new. I’ve seen inside A LOT of lab grade hardware from everyone from HP/Agilent/Keysight to Anritsu to Rohde & Schwarz to NI to Teradyne to Lecroy/Teledyne and they all do some pretty hacky stuff. Bluewires is the norm, not the exception… At this point I am kind of shocked when I don’t see some wire wrap wire bridging something, or decoupling caps tacked on like some afterthought or a pot replaced by a trio of resistors in some flux capacitor looking fashion.
    You kids need to take more stuff apart…

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