Hello Phil, OK - didn't know that about PWM - so used to plonking in caps with other PSU type things - will pull it out.
I do agree that it's looking like the oscillator isn't running - am basically going to pull the circuit apart on paper and trace each pad/ trace and component to ensure no errors, then replace the op-amp chip in case it cooked off. only issue I found on the first pass over the cct was the terminal for V+ had cracked when I tightened on the 2.5mm2 cable - so it wasn't making a reliable contact. - I ended up removing the the terminals for the supply and motor and drilled appropriate sized holes in the PCB and attached short lengths of 2.5mm2 cable going off to chocolate block terminal strip for a more robust connection.
either way this cct is coming out of the application and being replaced with one which doesn't have the 5s "soft start" option - the application here is a lather and it's disconcerting for the user to press the "start button" and then not have something happen within a second or so.
the embarassing bit is that I used to be reasonably good at the hardware side of things, but too many years in programming, it've fallen out of touch
- this was/ is my foray into trying to regain some familiarity - and it's fallen into a heap.
thanks all, i'll be in touch once I get this fixed (along with the PC which died, and sort out some other issues...) too many jobs, not enough time. Thanks again for the pointers, Des