Plussing-Up the Heathkit IP-18 & IP-2728

My 50-year-old Heathkit IP-18 power supply, which has been serving me all these decades, needed something extra...

[@hopelessnerd6677]

I miss Heathkit. The "new" Heathkit is only a shadow of its former self.

[@dtss_smudge]

The only "21st Century" Heathkit that interests me, and that I've built, is the GC-1006 clock. And even then I've heavily modified it.

[@Joe-fb4eg]

Where did you find them?

[@analog_guy]

I have one I use as an everyday go-to power source. I like it except for the current limiting scheme. The output current goes through the wiper of the current limit adjustment potentiometer. The potentiometer was not designed to handle this much current through the wiper nor to force all the power dissipation to be only in the portion of the resistive element between the wiper and the end. Thus, it is easy to damage the potentiometer and get erratic current limiting below spec. I haven't figured out any easy way to correct this. I was hoping you may have found a modification to correct this problem.

[@dtss_smudge]

Not a problem for me, as I use it intermittently, and almost always with the current pot set at max. I imagine it would not be too difficult to totally re-engineer it into the same enclosure with a more modern design and parts...

[@kenmore01]

Hi. I solved the problem by replacing the pot with a rotary switch and fixed resistors. I even wrote the current outputs on the front panel so I can select what I want.

[@analog_guy]

@@kenmore01 That's a good solution. It is the next best thing to a continuously adjustable scheme. I suppose the pot could alternatively be replaced with a MOSFET, but that would introduce a temperature-dependency that would need to be compensated if the current is to be kept at a fairly-precise value.

[@kenmore01]

@@analog_guy My solution will be to replace the guts entirely with a new more powerful circuit. Wish me luck! 😀

[@analog_guy]

@@kenmore01 Best wishes for success, and good luck!

[@Joe-fb4eg]

Oh nvm I didn’t wait long enough

[@dtss_smudge]

No prob. They're still on Amazon as of now.