Subject: Fujimoto CP-30 3H Slot 1 temp runaway / won't hold 35 C + drain hose size?

[yairs]

CP-30 3H (mechanical controls, no digital panel).
Symptoms (short):

• Slot 1: either runs away to ~55–60 °C or barely heats. The knob is hyper-sensitive, tiny turns change temp a lot. If I back it off, the heat can cut out and not come back until I turn it to the right, and then it goes nuts
• This started after an ~8-hour session where Slot 1 overheated; since then, 35 °C is not stable/repeatable.
• Slot 2: rock-solid at ~33.6 °C.
• Slot 3: unheated (OK).

Ask 1: What fails here typically?
For those who’ve fixed this exact behavior on a CP-30 3H: which component usually causes it, and what did you replace/adjust? Any quick mechanical calibration steps or checks you recommend?
Ask 2: Drains/tubing size:
The original hoses crumbled. I’d like to replace them and preferably use push-in tubing inside the drain bore (not over a barb). A wood dowel 8–10 mm fits (8 mm seems closer). What ID/OD tubing are you using successfully on CP-30 3H drains, and any inline-valve setup you like?
Photos, part numbers, and sizes would be super helpful.

I'd appreciate any help possible cuz I like it so much over a drum use
Thank you!

 

[mshchem]

Welcome to Photrio

 

[koraks]

Welcome to Photrio!

Ask 1: What fails here typically?

Sounds like a broken thermostat. Like the thermostat in fridges, ovens etc, they sometimes give up the ghost. These thermostats are based around a simple assembly of a bimetal contactor; this can get stuck (sometimes intermittently), wildly inaccurate (bent out of shape) or otherwise show intermittent operation due to e.g. corrosion or arcing of the contacts. Forget about calibrating it; there's nothing to calibrate there. Find a new thermostat. On sites like AliExpress there's a wide range of thermostats; you may be able to find something that fits the bill. The parts used in machines like these would be generic types you'd come across in all manner of equipment. The trick is to find a good substitute. Sometimes it's easier to just implement a new digital temperature control system around a PID controller or something.

Can't help you on the hosing; sorry. I'd probably order a bunch of different sizes in the hope something fits.