At IBM their motto was K.I.S.S. Keep It Simple, Stupid. Time is valuable, so is having a reliable and professional soldering station that I could easily construct myself quickly and cheaply.
I used the same soldering station pictured by JK27x for the basics. It provided the cabinet and handle holder for the Hackko Station conversion.
Just one on/off Sw, One knob on one pot to set temperature, just one LED for power indication, one LED to show the handle has reached the proper temperature.
My station automatically remembers the last temperature because the knob on the pot is already set to the correct temperature. No ROM look-up tables.
My controller requires no tweaking of op-amps, build it on a simple breadboard or perfboard, and just about any op-amp will work(LM741,4558, LM308,etc.) just must be an op-amp with max power supply rails >= +-12V.
The old station also had a 5-pin connect that could be adapted to the Hakko 8801 handle by removing the center pin from the Hakko connector..
Time to construct..about an hour to fabricate on perfboard. No digital display, no complicated calibration, all I had to do is just twist the knob to find the right temperature and bingo, calibration complete!
And the bonus is that I can also just plug in a Weller WTPTC TCP-7 700 deg F magnetically tip temp set handle | have by modifying its connector, just shorting pins 5-6 (thermistor connections) on its connector. This gives me an additional handle and tip to do work with interchangeable tips that automatically regulate temperature with very good thermal sensing. It also gave me a very good soldering tool that was easy to solder with to make my own Hackko.
I wouldn't waste any time buying that $1.50 handle I posted when a very good quality 888D handle is available at low cost.