HP-E3646A dual output power supply onboarding

HP-E3644A Dual output power supply

I've been looking for a decently priced dual-output PSU for a while and finally pulled the trigger on this almost-new E3646A, of recent vintage given the Keysight branding. In fact this is the first Keysight piece of equipment that I guy with the intention of keeping. Given how clean and new it looks there is probably not much to say, but hey, that hasn't stopped me before. Plus who knows what we'll find inside...

Always nice to see an intact calibration tag, but this is not going to stop me...

The power supply is easy enough to open, and this model doesn't have the badly designed rear bezel of many other HP instruments of the era (you know, those that are always broken when removing the bumpers). After getting rid of the calibration sticker we only need to remove 4 screws in the back as well as the two screws of the handle. Then we're in!

Inside the HP E3646A

The insides are nothing special and looks very similar to the other members of the E364xA series: transformer in the front, electronics in the back. The top board contains all the digital circuits and is quickly removed by removing two screws and sliding it off. Nice construction. Here's a quick shot of the verso of the digital board, which predictably only contains a few passives:

Back side of the digital board

After the removal of the digital board

We can also zoom on the four strange back-to-back transistors that are linked together with a white plastic goo. Never seen this type of transistor pairing (or heat dissipation).

Main board detail with strangely paired transistors

Now let's flip this baby and look at the back side...

Bottom side

... and discover some horrors! (?) At least things I don't like to see. First there's a bunch of fingerprint marks that seem to be made with solder mask. Therefor in the PCB factory. WTF?

Booo fingerprints

Then there's some white stains all over the board, likely from hand soldering of some components. Not nice.

White stains

Even more stains

The solder joints for the front panel terminals are also showing white marks. But we've seen so much already I'm going to give them a break. The joints themselves look a bit amateurish though. Not clean, some look like cold solder joints. Seems like I'll have to get there with some good ol' lead solder and fix this...

Not great soldering, more stains

Ditto

Finally we have to look at the mains input filter section because even though this model is very recent (built in 2019 or so), there could still be...

RIFA CAPS! Gaaaa!

Some are already cracked!

And some are already cracked. Booooo Keysight Booo! Anyway, there's some little odd things here and there that are not kosher but otherwise a great PSU, in full working order and in near-pristine cosmetic condition. Noice.