Pete Alcock Posted November 4, 2016 Share Posted November 4, 2016 Hi B-R, I've had to build a replacement PSU for a standard Canford/Tecpro intercom system after the PSU went missing. I've got the 24V OK, but it's the terminating impedance I can't get a unified view on. Some say 4k7 Audio to Gnd, plus 220R in series with 10uF Audio to GND. (Bluecom project)Others say 2k2 Audio to GND plus 220R in series with 1uF. (Another post on B-ROthers say just 2k2 audio to GND. (Crowley intercom) Does anybody know what's used inside a genuine Tecpro PSU? Thanks as always, Pete. Link to comment Share on other sites More sharing options...
DrV Posted November 4, 2016 Share Posted November 4, 2016 According to the MS741 manual recommended termination is 200ohms in the audio band and 5K at D.C. 4k7 in parallel with (220R and 10uF in series) is a pretty good approximation using preferred values Edit for spellcheck intervention! Link to comment Share on other sites More sharing options...
boatman Posted November 4, 2016 Share Posted November 4, 2016 Does anybody know what's used inside a genuine Tecpro PSU? Yes, see this post The real thing can be found here. Link to comment Share on other sites More sharing options...
Pete Alcock Posted November 5, 2016 Author Share Posted November 5, 2016 Dr V, Boatman, Many thanks for your help on this, and for the circuit. Yep, all completely clear now, and I can finish the job. Hope I can do the same for you one day. Cheers, PA. Link to comment Share on other sites More sharing options...
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