Hi Antonshutte , I understand I read your Forum today and I am also a Owner of this Yizreel Electronics Osiciloscope OS3 which I bought during my sturdy in Electronics in Lodon during 1978 ... Now this Scope has been Btoken down for years ans I lost the User Manual with Circuit o it ... I hope by now you may already got the Circuit diagram and I wish you could send me a Copy in order I can do a repair on it . Thak you very much for your kindness . I remain.