Telefunken S500 Turntable Speed regulation problem - Page 1
Forum section: electronics / repair

author: Matthew98
author_rank: Regular Contributor
timestamp: February 11, 2019, 12:28:50 pm
content: Hey, guys !I have a Telefunken 6001 hifi with S500 Turntable platform and Im really close to it being in pristine condition. There is a problem with speed regulation on the platform. After lets say ten minutes of playing or so it decides to run for it. It will keep speeding up until i stop it. That was at 33 rpm. I believe 45 worked fine even after that. Turn the turntable off for a minute, turn it on and its working great again. Any idea what could it be ? I cleaned the trimmers for the speeds, but no change.The turntable tends to get quite warm when playing, so it might have something to do with that. With luck its gonna be just a loose connection somewhere.Im sorry for asking before looking myself, but this turntable is quite valuable, my opening window to audiophile experience and I would kill myself by ruining itPs. Also, the circuitry for picking up the needle when it reaches end of the record doesnt work. I believe that the optical resistor (sorry, cant remember the name) just got old... Dont know if that is reusable or even If there is a potentiometer to set the sensitivity, but would appreciate any help on those problems.Thank you guys so much !

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 12, 2019, 12:19:54 am
content: Looking at schematic on Elektrotanya:https://elektrotanya.com/telefunken_s_500_hifi_sch_print.png/download.htmlThere are 4 electrolytic capacitors. C118 is not likely to be the cause, at least check voltageandripple at C117 and C111.If power is clean move on, you've cleaned the speed trimmers but have you cleaned (and measured values?) of all 4, the 2 on the table and the 2 on the PCB? Also clean contacts on PCB connector.Once you have been through this, I'd name 2 other suspects: C113 on tacho feedback and T109 on motor control. (BC338/25 I've seen plenty of these go wonky when warm...)For the auto-stop, light dependent resistor (LDR) is the name you are after, could be bad, could be dirty. Sensitivity is on trimpot R116.

author: floobydust
author_rank: Super Contributor
timestamp: February 12, 2019, 12:33:50 am
content: +1I would replace all electrolytic capacitors, this is 45 years old and they dry out. There are only 4.C118 - 220uF 16VC117 - 1,000uF 25VC113 - 47uF 10VC111 - 10uF 35V

author: Marin-Pache
author_rank: Newbie
timestamp: May 17, 2023, 06:26:12 am
content: Bonjour,Ce sujet a déjà été traité mais demeure assez ancien.Ma platine fonctionne bien pour une vitesse de 33 tr, mais en 45 tr elle s'emballe et en position stop au bout de quelques minutes elle se met a tourner et accélérer avec un faible couple moteur.J'ai mesuré les composants résistances et transistors, qui semblent bon, changé les chimiques.J'ai remplacé le transistor T109 qui pilote le moteur par un plus puissant mais aucun changement.Sur le schéma d'implantation, le collecteur et l'émetteur du T104 semble inversé.La valeur mesurée sur le collecteur du T104 n'est pas du tout dans les valeurs préconisées, et les potentiomètres R131 et R132 ne sont d'aucune efficacité et sont mesurés bon.Merci si quelqu'un peut me guider dans mes recherches