I have purged 4 times and so far with no errors. Also have tested a handful of times with the vacuum test on the machine. Got the 1000W step down on Amazon for $59 and used the Craftsman $35 2.5 gallon wet dry vac (smallest I could find) from Lowes since the original one was 8L. Had to wire the plug from the shop vac onto the step down to work with the end on the printer, they do sell the same plug at Lowes, but didn't see it till after I wired it. Wasn't any big deal since the shop vac was burnt up anyway.
Here are the links:
Step Down:
https://www.amazon.com/dp/B07XQ5WYF7?psc=1&ref=ppx_yo2ov_dt_b_product_details
Vac:
https://www.lowes.com/pd/CRAFTSMAN-2-5-Gallon-Corded-Portable-Wet-Dry-Shop-Vacuum-Corded/5013057707
If all goes well, I will probably check it in 6 months, because the old one was burnt up and I read somewhere that someone's caught on fire. I purchased this machine used about 4 months ago so not sure if it has been changed before, but I am guessing so based on what I have read. I added white ink to the machine and it purges a lot and I don't want it to catch on fire at night or weekends when no one is here. Seems like the machine trashes more white ink than it actually prints. Seems about as half baked as using a $35 shop vac and charging $550 for it.
Also, does anyone know where to get the printheads for the HP750 that are not thru HP? I think I read they are a Richo Gen 3 printhead? Can anyone confirm or share where you get? Seems like they are close to $2k thru HP.