CONRAD Elektronics is possibly Germanys largest and certainly the most popular Electronic Parts Reseller. Some time in the 1980s i bought a stabilized 13.8V, 3A (5A) DC Power Supply that served my needs for decades now. Lately i accidentally dropped it to the floor and after re-checking it, it seems to send out pretty much “unregulated” 22.7V DC Power to the output jacks. Since its still handy to have a regulated little PS around i want to try a repair action on it.
Sadly neither CONRAD nor the Internet seems to have the Schematics online, so i started to investigate and reverse-engineered it. I put all Parts as far i was able to identify into a EAGLE Cad Schematic incl. Values and all. Those Parts i was not able to identify i unsoldered and measured manually. Like the strange looking Zener-Diodes with their ugly pretty much non-speaking Labeling.
Here are the Schematics i finally hammered together in EAGLE. Click on Image to enlarge or download PDF or Schematics.
UPDATE: The Schematics now should be pretty much CORRECT. The T2 Transistor BD317 (TO3 Casing) is a NPN type. Dont get confused by some obscure DataSheet on the Internet saying it would be a PNP. The SF826D (T1) ist also a NPN universal purpose Transistor. However if you still found a mistake, please let me know by sending me an eMail to firstname.lastname@example.org.
UPDATE: The Power Supply meanwhile has been fixed. Thanks to some gentle Users on Dave Jones's EEVBlog Forum who gave me the final hint, i was able to measure a DEAD T1 which been conducting all the time. The Transistor seemed to conduct from Collector to Emitter and vice versa without any Base-Current. I replaced it with some rotten desoldered BC338 i had lying around since the 80s :). The Circuit is not very good on stabilizing compared to modern Voltage Regulators. Without a LOAD it provides round about 14Volts while on pulling about 2.5-3A it drops down to about 13V. However, its good enough for most everyday Apps.
THANKS TO ALL THE USERS ON THE EEVBLOG FORUM WHO HELPED ME WITH THAT! THANKS TO ANY MAKER WHO FREELY SHARES KNOWLEDGE, VIDEOS, TUTORIALS AND OTHER FREE LEARNING MATERIAL ON THE INTERNET! Keep information free for everyone!
THANKS and C U! — Axel Werner 2011-11-06 22:45