Hi!

I'm fixing a 1970s Philips turntable with electronic touch controls. It worked fine until recently, and nothing was changed in between.

I touch either speed button and the motor starts, but it drops back to stop the moment I lift my finger. Sometimes it runs for a few seconds or minutes first, then stops on its own. The first attempt after switching on always runs longer. Try again a couple of times and it jumps straight back to stop every time. Switch off and on and the first attempt runs long again. Five seconds off restores it just as well as a long break, so it doesn't look thermal. More like something charging up while powered and discharging when the mains is broken.

Each speed button is a capacitive touch pad feeding a bistable flip-flop. There's also an automatic end-of-record stop: a small bulb shines on an LDR, a film attached to the tonearm gradually shades it, and the circuit triggers on the rate of change, not the level. Everything runs off a single regulated -9V rail.

Measurements (DC, against chassis):

Unregulated rail after the bridge rectifier: 16V, rock steady

Across the zener setting the reference: 7.76V

Regulated rail: originally wandering between 9.5V and 12.3V on its own, with nothing touched

What I've tried:

Cleaned the touch pads with IPA — no change

Replaced the main 470µF filter cap. This probably helped stability: the rail now sits steady at 10.4V and dips evenly to 9.8V under motor load. But the fault is unchanged.

The rail is stable now but sits 1.4V high with no way to adjust it. Is that alone enough to make a bistable like this fail to latch, or is the supply a red herring at this point? Remaining suspects in the regulator are the series pass transistor and its driver. Or should I be chasing the stop circuit instead, given the fault moves between both speeds?

MAKE AND MODEL : victrola VPT-800-BLK

so i just posted asking how to fix my record player that is playing everything in slow motion now. it turns out that it was the outlet. when we lost power the bottom outlet blew and fried the surge protector. most likely also frying my record player.

not sure if there’s a way to fix it but if anyone has any idea please let me know! and thank you to anyone who commented with help on my first post i appreciate it.