The topic of function generators came up at Squidwrench a while ago (Sophi was tinkering with LCD shutters) and I finally picked up one of those JYE Tech FG085 DDS function generators to see how they work:
Short answer: adequate, if you’re not too fussy.
The board arrived with a bizarre solder defect. It seems a solder stalk yanked one terminal off a ceramic SMD caps:
The schematic and adjacent parts suggested the victim was a 10 uF cap, so I replaced it with one from my stash that worked fine.
However, after soldering enough of the switches to do something useful, the board wouldn’t power up. With a bit of poking around, I discovered the power jack had +15 V from the wall wart, but the center terminals on the DPDT power switch that should have been connected to the jack showed maybe 0.3 V. Jumpering around the failed via and a short trace on the bottom surface let the board power up correctly:
If you’re building one of these, solder one pin of each switch, push all the switch caps in place, shove the faceplate over all of them, tape it to the PCB, make sure all the switches are push-able, then solder the remainder of the switch pins. If you do them one by one, you’re certain to end up with a few mis-aligned switches that will either prevent the faceplate from sliding over them or wedge firmly against the side of their assigned hole. Just sayin’.
It lives in a case from Thingiverse:
I tweaked the dimensions slightly to fit the (slightly larger, possibly new, maybe tolerance-eased) front panel, but the bottom mounting screw hole spacing depends on the front panel size, not a specific set of dimensions, leading me to relocate those holes by abrasive adjustment. I didn’t bother with the lid (which doesn’t clear the BNC jack anyway) or the printed plastic feet (having a supply of silicone rubber feet).
The fancy vent gridwork along the sides printed surprisingly well, even in PETG. I’d have gone with larger slots, although I doubt the thing really needs vents in the first place.
The DDS sine wave output is rough, to say the least:
The spectrum shows oodles of harmonic content:
A closer look:
Stepping back a bit shows harmonics of (and around) the 2.5 MHz DDS sampling frequency:
For comparison, my old Fordham FG-801 analog function generator has nice smooth harmonics:
Closer in:
Of course, that crusty old analog dial doesn’t provide nearly the set-ability of a nice digital display.
The Smell of Molten Projects in the Morning 
Hi Ed, I don’t think I would buy one of those simply based on the build quality of the PCB. Most of the components shown in your pics are really poorly soldered. Whoever soldered it needs training.
Well, I’ll take credit for the crappy jumper soldering… [grin]
The rest came directly from their wave soldering tank, so perhaps a temperature control issue produced that stalk and the granular SMD fillets. Although we’ll never know the rest of the story, some of the comments on the product page suggest this isn’t the only not-quite-right PCB in the wild.
That cap with the solder stalk is the only one of the bunch that actually shows signs of the solder wetting the terminals. My SWAG is that the wave solder was too cold/parts not terribly clean, and the stalky part was hand “repaired”. OTOH, my brief experience with surface mount manufacture dates to the mid ’70s, so take it with some salt.