Philips PM5110 RC Generator 10Hz to 100kHz 1986 test teardown

[@fredsmith5473]

It's a Wien bridge oscillator stabilised by either a special thermistor (not an incandescent lamp) for low distortion, or some other means for fast settling but higher distortion, as set by the switch on the back. I have one and checked the distortion with an HP8903E. IIRC it was 0.008% at 1 kHz and became higher towards the low end and over a few kHz. That's what you'd expect for a good design stabilised with a thermistor, and is enough for most distortion testing. There are audio generators which produce much lower THD, but the PM 5110 is small and light. I could never find much about the PM 5110 on the WWW, but when I just looked Elektrotanya now has a service manual, which consists of a circuit diagram only. It would be nice to have the set up procedure and parts list, but the circuit diagram on its own is very useful. The frequency calibration on mine was slightly out, but it was got right by carefully altering the presets. After all, it's a Wien bridge oscillator.

[@Edisson.]

Hi Thomas, the THD is luxurious, it's funny how the curve on the oscilloscope swings like a monkey on a rubber band when switching. I have an arrow-shaped LED in the PWM controller I made as a source for microtools - they show me the direction of rotation. Nice day 🙂 Tom

[@CornelisJoh]

In my experience, when I post links (URLs) in a comment, the comment gets automatically deleted (or is made invisible) by youtube. Anyway, some information including specs of the PM5110 can be found in a document named "Philips-1987~8Cat-p209~226_600bw". It is a pdf document on the website of a company called casa. Since I have not mentioned a direct link, I hope that my comment is not deleted by youtube.

[@TeardownOZ2CPU]

Thanks it is a good trick, and thanks for the info

[@Sine1040]

These triangle LEDs are getting more difficult to find, 20 years ago they where no problem since they where used in tape drives and the sort.

[@TeardownOZ2CPU]

i dont think i own a single one.. lucky this one works, if broken i would most likely just glue a tiny white led to its back side, and solve it that way.