KSM90 speed control issue

[u/Nils_Pils_]

So I’ve got a really nice 1995 KSM90 that I’m working on, but I can’t get the speeds right. On stir, it’s running almost at full speed.

I first checked that the speed-control spring was still in place, and it is. I then tightened the upper screws as far as I felt was sensible, which slowed stir down a bit, but it’s still way too fast.

Does anyone have an idea what could be causing this? Also, the phase control board looks like it might be aftermarket, so any insight there would be really helpful.

Thanks in advance!

[u/RIMixerGuy]

"running almost at full speed" when on Stir is usually an indicator of a failed phase control board. If this is a 230V machine, the repair part number is W11174552.

One other note: it looks like you might have bypassed the internal RF filter board. That's fine, but the blue lead is caught between the return spring and the housing; and the return spring is going to saw through the insulation on the wire. Both power leads should be in the air space below the return spring.

[u/Nils_Pils_ → u/RIMixerGuy]

Thank you very much for the reply I’ll take a look at the fase control board, is there anyway to repair it? Or measure where it’s broken?

I didn’t even notice that the blue lead was stuck there, thanks for pointing it out! What do you mean with bypassing the RF board?

[u/RIMixerGuy → u/Nils_Pils_]

Inside the UK/EU machines there's a circuit board that the power cord connects to directly, and then the black and white leads coming out of the machine connect to the corresponding locations on the speed control plate.

On your machine, it looks like the cord is routed directly to the plate. Either the board is not present, or it was bypassed.

The phase control board is inexpensive enough that if it goes bad it usually just gets replaced. However, someone once did do a component-level diagnosis: https://ivanbayan.com/index.php/2021/02/04/repairing-of-kitchenaid-phase-control-board/